RICERCA ITALIANA     

Diagnostic and therapeutic implications of the new clinic and molecular knowledges of medullary thyroid carcinoma del .

Università di Pisa

Abstract

BACKGROUND: Medullary thyroid carcinoma (MTC) is a well-differentiated thyroid tumor that arises from C cells. It is a rare neoplasia with a prevalence of 5-10% among all thyroid cancer. Mutations of RET gene are the unique genetic alterations found in MTC. Both somatic and germline RET point mutations are able to constitutively activate the intracellular MAP kinase pathway, which ends up in a uncontrolled cell proliferation. RET point mutations are responsible for the development of virtually all inherited MTCs and of about 40% of sporadic MTC. However 60% of sporadic MTC are still “orphans” of causative oncogene. Since the clinical and pathological features of RET positive and RET negative MTC are very similar, it is conceivable that the same MAP kinase pathway activation can drive the tumoral transformation in the two groups. Other mechanisms of RET activation should be explored as possible alternative causes of MAP kinase pathway activation.
Genetic screening of RET gene is now a powerful diagnostic tool for MTC. Even if this discovery greatly improved the diagnosis of MTC, the definitive cure of the MTC patients can be achieved only in case of an early diagnosis and a total thyroidectomy, performed when the tumor is still intrathyroid. Therefore, the survival rate is 50% at 10 years and decreases to 10% in cases with distant metastases at diagnosis. At present no markers of tumor progression and no specific prognostic factors are used in the clinical practice.
AIMS: The project is planned to investigate the weakest aspects of MTC clinical management: the pathogenesis of RET negative cases, the prediction of the outcome and the therapy of advanced and metastatic MTC. To develop the project we will focus into 3 major objectives: a) analysis of the molecular features of MTC and identification of alternative mechanisms of tumoral transformation. b) identification of new prognostic factors and new disease biomarkers; c) identification of target therapies in advanced MTC.
PROCEDURES: to reach the 3 objectives, the 5 Units involved in the proposal and characterized for their specific competence on the MTC research field, will collaborate to develop the following tasks: a) To improve the knowledge of molecular features of MTC new RET mutations will be characterized, and RET positive and negative MTC samples will be compared at molecular level. The activation of MAP kinase pathway will be verified in RET negative cases and, if confirmed, alternative mechanisms of RET activation, such as RET mRNA overexpression or gene amplification, will be searched for. Alterations of other intrasignalling cascades (eg Notch pathway) will be also evaluated. The possibility to have activating mutations in tyrosine kinase genes other than RET will be also studied [this part of the project will be mainly developed by the Units of Pisa, Naples and Rome] b) The role of the RET mutations and polymorphisms as prognostic factors will be assessed by correlating their presence with the clinical and pathological features of patients and their final outcome. Since in animal models the alteration of RET signalling is associated with kidney disgenesis, the frequency of renal malformations in patients affected by hereditary MTC will be compared with that in patients with sporadic MTC. For the identification of new prognostic and diagnostic markers, the comparison of serum and tissue proteomic profiles of different groups of patients affected by MTC, such as sporadic and hereditary, RET positive and RET negative, etc. will be analysed [this part of the project will be mainly developed by the Units of Pisa, Siena and Perugia] c) To find new therapies for cases unresponsive to conventional therapy some new developed tyrosine kinase inhibitors, already shown to be highly effective in vitro, will be tested on advanced MTC patients. Furthermore, the in vitro anti-neoplastic effects on MTC cells of new pyrazolo-pyrimidine derivates will be analyzed, with special attention to the possible inhibition of the activation of the MAP kinase or Notch pathways. Finally, the possible role of tyrosine kinase inhibitors or COX-2 inhibitors as adjuvant for conventional chemotherapies, which are poorly effective for the treatment of advanced MTC, will be in vitro investigated [this part of the project will be mainly developed by the Units of Rome, Pisa]
EXPECTED RESULTS: this research should be able to find new RET mutations and/or other mechanisms of activation of the MAP kinase pathway especially in RET negative cases. New molecular and serum biomarkers to be used both to predict the aggressiveness and the prognosis of the MTC are also expected. New drugs and/or therapeutic strategies should be obtained with the in vitro and in vivo studies. All these results should allow to greatly improve the clinical management of this rare but lethal disease. <<<

Principal Investigator

Rossella Elisei Università degli Studi di PISA

Research Objectives

The general aim of the present project is to investigate the molecular features of Medullary Thyroid Carcinoma (MTC), to identify alternative mechanisms of tumoral transformation, to find out new prognostic factors and to identify new therapies. Since this thyroid neoplasia is rare (0.05-0.1% of all human tumors) the studies are always performed in small series and with short term follow up. Despite its rarity, it is a killing tumor and the survival rate at 5 years is 50% and decreases up to 10% when the tumoral stage at diagnosis is advanced. Conventional therapies, such as chemotherapy and radiotherapy are ineffective and are only used as palliative therapies. Since the pathogenesis of MTC is related to the activation of RET protooncogene, which encodes for a tyrosine kinase receptor, new tyrosine kinase inhibitors are under development and clinical evaluation. However, while 99% of hereditary MTC are associated to RET germline mutations, only 40-50% of sporadic MTC show a somatic mutation of this gene. It is conceivable that other oncogenes or other mechanisms of RET activation may be responsible for the tumoral transformation of the remaining 50-60% of MTC cases. Thus, the identification of these alternative mechanisms or genes involved in the development of MTC will be of great clinical impact not only for better understand the pathogenesis of the tumor but also for the development of other new therapeutic strategies that are really urgent for these patients.
The present project is aimed to reach 3 main objectives:
• OBJECTIVE 1 Analysis of the molecular features of MTC and identification of alternative mechanisms of tumoral transformation.
This object is aimed to better understand the molecular mechanisms of tumoral transformation and in particular to analyze the possibility that other mechanisms than point mutations could be responsible for the activation of RET gene and, as consequence, of MAP kinase pathway. This objective will be developed through the realization of specific aims:
a) identification of classical and new RET point mutations in a large group of MTC;
b) analysis of the biochemical and biological features of RET rare mutants that have never been studied with respect to their property of activating RET
c) identification of alternative mechanisms of RET activation, in particular RET mRNA overexpression and gene amplification, to explain the pathogenesis of RET negative cases;
d) analysis of the sequence of tyrosine kinome (90 genes encoding for all the tyrosine kinases present in human genome) in different types of MTC (familial, sporadic, RET-positive and RET-negative), in order to explore whether, beside RET, any other tyrosine kinase is mutated in such tumours;
e) analysis of the kinase activation in different types of MTC by determining the relative level of phosphorylation of Receptor Tyrosine Kinases and several serine/threonine kinases, in both MTC cell lines, primary culture and tissue samples.
Beside the RET pathway, different mechanisms of tumoral transformation are known. For this reason we will also:
f) evaluate the expression and alteration of the Notch pathway members and their target genes firstly by using in “in vitro model” (MTC cell lines) and thereafter by using human MTC tissue samples, taking into account the presence or absence of RET somatic mutation.
• OBJECTIVE 2 Identification of new prognostic factors and new disease biomarkers
Since the success of the therapy is mainly related to the early diagnosis and completeness of the surgical treatment, new biomarkers specifically related to the presence of MTC are desirable both to anticipate the diagnosis and to predict the degree of aggressiveness. Some insights on the possible role of RET somatic mutation as prognostic factor have been already reported. However, published series are small and with short term follow up. Further studies are required to confirm these data and also to find alternative markers.
It is known that RET proto-oncogene and its ligand GDNF play also an essential role in renal morphogenesis. The recent evidence of an association between hereditary MTC and renal abnormalities, arose the question of whether this association was occasional or related to the RET mutation. The possibility that a new disease (eg renal/urinary abnormalities) might be included in the multiple endocrine neoplasia syndrome and its relationship with specific RET mutation will be explored
For the development of this objective the following aims will be pursued:
a) evaluation of the role of somatic RET mutations and RET single nucleotide polymorphisms (SNPs) as prognostic factors in a series of MTC with a long term follow-up;
b) correlation of RET mutations with renal malformations in patients with hereditary MTC and, as control, in patients with sporadic MTC;
c) analysis of screening of the glycoproteins expression profiles in serum and tissue samples of MTC patients and correlation between profiles of RET positive and RET negative cases
OBJECTIVE 3 Identification of target therapies in advanced MTC
Since MTC patients that are not cured at the first surgical treatment are refractory to conventional therapies, new therapeutic strategies are needed to treat these patients. Aim of the project is to study new therapeutic strategies based on MTC cell proliferation blockade, by interfering with the hormonal growth signaling. In this part of the project alternative treatments will be evaluated both in vitro and in vivo.
Aims of this objective will be:
a) to investigate the in vitro effects of COX-2 inhibitors on the growth rate of MTC derived cell line and especially the possibility to increase the effect of drugs, such as vinorelbine, in the treatment of MTC patients.
b) to assess the antiproliferative effects of a series of molecules, pyrazol-pyrimidine derivates, acting as inhibitors of tyrosine kinase proteins involved in signal transduction or modulation of cellular proliferation in MTC cells.
c) to analyse the presence of a synergistic effect by combining the tyrosine-kinase inhibitors with known antineoplastic drugs
d) to evaluate the MTC cell lines response to tyrosine kinase inhibitors (pyrazol-pyrimidine derivates) according to Notch pathway status
e) to evaluate the therapeutic efficacy and clinical benefits of some specific tyrosine kinase inhibitors in clinical trials. <<<

First Results

The main purpose of this proposed project is to investigate some molecular aspects of Medullary Thyroid Carcinoma (MTC) that should allow to identify alternative mechanisms of tumoral transformation and find new markers for the diagnosis and prognosis of this very rare disease. New therapies will be also searched for because, when advanced and metastatic, this tumor is lethal. We feel that the project will end up in very important results with great clinical benefit. The strength of the project is the network of these 5 units that, although with different interests, are all involved in the research on MTC. Furthermore, since the MTC is a very rare disease (0.05-0.1% of all human tumors) only the collaborations of referral centers such those involved in the project may guarantee a relative high number of both tumoral tissues and patients to be included in the different aspects of the research. The results we are planning to obtain can be distinguished according to the 3 different objectives we would like to reach. Here following are the details of the predicted results and the clinical benefits that can derive from them.

OBJECTIVE 1 Analysis of the molecular features of MTC and identification of alternative mechanisms of tumoral transformation. In the framework of this objective we expect to identify the molecular features of MTC and to clarify alternative mechanisms of tumoral transformation. In particular there are 50-60% of sporadic and 1-2% of hereditary MTC that are orphans of genetic alterations. Neither RET mutation nor other known oncogenes, such as p53, BRAF, RAS etc, have been demonstrated to be involved in the pathogenesis of these RET negative cases. Other oncogenes or tumor suppressor genes and/or other mechanisms of RET activation are likely involved in the tumoral transformation of the orphan group. In this context we expect:

a) To find new RET mutations, especially in those part of the gene less frequently analyzed, and to demonstrate their functional and transforming activity.
b) To identify alternative mechanisms of RET activation in RET negative MTC cases such as the overexpression of RET mRNA and/or the gene amplification. Both mechanisms could lead to the activation of RET gene independently from the presence/absence of the most common point activating mutations.
c) To verify if the activation of the MAP Kinase pathway plays a role also in the tumoral transformation of RET negative MTC. The levels of phosphorilation of downstream proteins like ERK will definitively reveal if the MAP kinase pathway is activated also in absence of RET mutations. In this case different modalities of activation of the MAP kinase cascade will be searched for (ie other tyrosine kinase gene alterations, RET mRNA overexpression or RET gene amplification).
d) To identify mutations in other human tyrosine kinase genes than RET which could also be involved in the pathogenesis of MTC, especially in those cases with a clear activation of the MAP kinase pathway but without an evident somatic or germline RET mutation.
e) To find alterations in intracellular pathways different from the MAP Kinase pathway. In particular we expect to find some impairments in the Notch pathway, either in its members or in their target genes.

We feel that, at the present, the research on MTC is progressing very slowly. After the identification of RET gene mutations as causative of hereditary forms of MTC, no other oncogens have been searched for in those cases with no RET mutations. The results we are expecting to obtain by reaching this first objective of the project will improve significantly our know-how on the pathogenesis of this rare but aggressive human tumor. From a practical point of view, to know the alternative mechanisms leading to the tumoral transformation of RET negative MTC cases will also allow to develop new drugs and new therapeutic strategies devoted to inactivate those altered mechanisms.

OBJECTIVE 2 Identification of new prognostic factors and new disease biomarkers The development of this part of the project should lead to the definition of RET gene mutations and SNPs as prognostic factors of the outcome of the disease. A better definition of involvement of other diseases, such as renal malformations, in the multiple neoplasia syndromes and their correlation with specific RET mutations is also one of the expected results of this objective. Finally, we also expect to find new proteins to be used for both the early diagnosis and the prediction of the aggressiveness of the disease and, as consequence, of the outcome. In particular we expect:
a) To clarify the correlation between the different RET mutations and the clinical and pathological features, as well as the outcome, of MTC patients.
b) To confirm the role of RET mutations as prognostic factors by comparing the outcome and the survival rate of a big group of patients with RET positive MTC tumors with a comparable group of RET negative MTC cases.
c) To definitively identify the role of one ore more SNPs as predisposing factors to the development of the tumor and/or as indicators of the aggressiveness and/or outcome of the MTC.
d) To verify if renal malformations may be part of multiple endocrine neoplasia (MEN) syndrome and if their frequency is similar in patients with hereditary MTC compared to those with sporadic MTC.
e) To find new sera biomarkers which could suggests the presence of a MTC hopefully at a very early stage. A specific serum protein pattern could be identified for MTC patients and be able to distinguish these subjects from others affected by different thyroid tumors (ie papillary or follicular thyroid carcinoma)
f) To identify specific tissue biomarkers significantly different in normal and tumoral tissues. Proteomic analysis of normal vs tumoral tissue could lead in the identification of proteins specifically expressed in the tumor. Similarly the comparison between RET positive and RET negative cases by proteomic analysis might allow to identify specific patterns of proteins expression

The results we are expecting to obtain by reaching this second objective of the project will be, in our opinion, of great clinical benefit for several reasons. First, they will help the clinical management of MTC patients because the prognostic factors will help the medical team to have a clear idea of the aggressiveness of the disease and then to chose and plan the most appropriate therapeutic strategies. Cases with bad prognostic factors will be treated more aggressively and clinical controls during their follow up will be more frequent. The identification of other diseases to be definitively included in the MEN syndrome will indicate to physicians the opportunity to evaluate also those organs that could be involved, as for example the kidney and the urinary tract. Second, the identification of serum and/or tissue biomarkers by proteomic analysis will allow to easily perform a specific diagnosis of MTC by using just few milliliters of blood or few cells extracted from tumoral tissues by fine needle aspiration. At present these are only futuristic applications but we hope that the expected positive results of this research can contribute to the development of these kind of new diagnostic approaches.

OBJECTIVE 3 Identification of target therapies in advanced MTC With the fulfillment of this objective we expect to identify new drugs or new and alternative therapeutic strategies to improve the treatment of MTC, especially for the cases with a poor prognosis. Advanced and metastatic MTC are incurable at the present and we urgently need some other therapeutic options for these patients. First of all we expect to prove that the new tyrosine kinase inhibitors molecules are effective in vivo. In the meanwhile other more conventional strategies should be explored and we expect to find the way to improve the results of the more conventional therapy by adding some adjuvant drug. Finally other alternative drugs directed against other intracellular pathways such as Notch 1 could also be of clinical benefit especially for cases in which the MAP kinase pathway might not represent the altered mechanism leading to the tumoral transformation. In this context we expect:

a) To prove the clinical benefit (eg stabilization of the disease or, even better, the partial remission of the disease) of the tyrosine kinase inhibitors especially of those clearly directed against RET gene. These drugs have been already tested in vitro with very good and promising results. They hopefully will work also in MTC patients.
b) To find that some molecules, such as pyrazol-pyrimidine derivates, can act as inhibitors of tyrosine kinase proteins involved in signal transduction or modulation of cellular proliferation in MTC cells. Both the MAP kinase and the Notch 1 pathways will be explored with the aim to demonstrate the inhibition of at least one of the two.
c) To in vitro demonstrate that COX-2 inhibitors, usually used for the treatment of arthritis and neoplastic pain may increase the activity of drugs such as vinorelbine that is used for the treatment of progressing MTC as an alternative to the well proven ineffective doxorubicine. An increase of the percentage of patients with a stabilization of the disease from 30% to 50-60% will be of clinical relevance.
d) To demonstrate that the combination of tyrosine-kinase inhibitors with known antineoplastic drugs may have a synergistic effect and be more effective in the control of cell growth.

With this third objective of the project will expect to improve the field of the therapeutic strategies for the patients affected by MTC. It is known that those cases with advanced and progressive disease are at present undoubtfully without any possibility of survival. They are insensitive to conventional therapies and only in few cases we can obtain a stabilization of the disease (20-30% of cases) with chemotherapy: a very high price fro a low benefit. The results we are expecting from this part of the research are very ambitious but not impossible to be reached. New drugs have been successfully developed in the last years for other human malignancies which were previously considered without any possibility of cure. We feel that at least some of the expected results of this objective might greatly improve the clinical management of these patients. A prolongation of their survival if not the complete cure is not far to be obtained and this research can contribute to reach this goal. <<<

Timescale

24 months

National and international background

Medullary thyroid carcinoma (MTC) is a well-differentiated thyroid tumor that arises from parafollicular or calcitonin-producing C cells of the thyroid. It is a rare malignant neoplasia with an unknown incidence and a prevalence of 10% among all thyroid cancers, which are the most frequent endocrine malignancies and represent 1% of all human tumors. The clinical relevance of MTC is its high rate of mortality which is 50% at 10 years and increases up to 90% in cases with distant metastases at the diagnosis. The possibility to definitively cure the MTC affected patient is impaired by the extrathyroidal invasion and/or the presence of metastatic lymphnodes at the time of first surgical treatment.
Calcitonin is the specific and sensitive marker of MTC both at serum and tissue level. Serum CT should be measured in patients with thyroid nodules for the early diagnosis of the tumor. It can be also used for the follow up and the monitoring of the metastatic disease. CT can be also searched for by immunohistochemistry on the tumoral tissue for confirmation of diagnosis. Scanty data are available on the role of serum CT as prognostic factor. No differences in serum CT values have been reported between RET positive and RET negative cases. Since serum CT plays a dominant role in MTC diagnosis, no other biomarkers have been characterized. New tools such as proteomics may be used to discover new MTC biomarkers which might either suggest the presence of the disease or predict prognosis and response to therapies.
In about 25% of cases, MTC is a hereditary disease characterized by the association of multiple endocrine neoplasia (MEN 2). In 1993, two independent groups reported that activating germline point mutations of RET proto-oncogene, located on chromosome 10, were associated with hereditary MTC. After these first reports, several RET germline mutations spread in exons 10-11 and 13-16, have been discovered and found to be associated with 99% of MEN 2 syndromes. MEN2 is characterized by the presence of tumours in tissues derived from neural crest and displays three different clinical varieties, MEN2A, MEN2B and Familial Medullary Thyroid Carcinoma (FMTC). In particular, all three forms present Medullary Thyroid Carcinoma (MTC); additional features are found in MEN 2A (pheocromocytoma and parathyroid adenoma) and in MEN 2B (pheocromocytoma, mucosal neuroma and ganglioneuroma of the intestine) patients. Up to now no other diseases have been found to be associated to the already well known endocrine neoplasia included in MEN 2, however it is known that RET proto-oncogene and its ligand GDNF play also an essential role in renal morphogenesis. During fetal development, the receptor tyrosine kinase encoded by the RET proto-oncogene is expressed in a variety of tissues, including the peripheral and central nervous systems (i.e., neuroblasts of enteric nervous system), cells derived from the branchial arches (including the parathyroid), cells derived from neural crest (including C cells of the thyroid and adrenal medulla) and tissues of urogenital system. Both GDNF and RET null mice display severe renal abnormalities (agenesis or severe dysgenesis) and lack enteric neurons in a pattern that recalls human HSCR. Despite these findings, only few cases of renal agenesis have been reported in HSCR patients and, until 1998, no cases of renal malformations have been described in patients with FMTC. In 1998 a family in which FMTC was associated with renal agenesis and HSCR was described. This association suggests that also in humans, as in mouse and rat, RET mutations may produce renal abnormalities. Whether less pronounced renal abnormalities, symptom-less, may be present at higher frequency in patients with hereditary MTC is not known, because no systematic screening for renal abnormalities has ever been conducted in these patients.
Over 90% of MEN 2 carriers displays germline point mutations of RET gene encoding a Receptor Tyrosine Kinase. The position of mutations along RET sequence correlates with the three different MEN 2 phenotypes. The majority of MEN2A and FMTC mutations affects one of the extracellular residues of the cysteine-rich domain of RET (C609, C611, C618, C620, C630, C634); MEN2B patients carry two mutations located in the intracellular domain and consisting in 93 % of cases of M918T substitution and in only 3 % of cases of A883F substitution. FMTC is also associated to mutations of the tyrosine kinase domain (E768D, L790F, Y791F, V804L, V804M, S891A). Amplification of the mutant allele or loss of the wild-type RET allele might also occur as a second hit in MEN2 tumour samples. Very interestingly, somatic RET mutations are frequently found also in sporadic MTC with a frequency of about 40%. Moreover, RET-positive MTC seem to be characterized by a more aggressive clinical behaviour compared to RET-negative MTC. The molecular bases of such diversity are poorly understood, being obscure the genetic changes that underlie RET-negative MTC.
There are controversial data, obtained in small MTC series with short term follow-ups, on the prognostic role of somatic RET gene mutations. In particular no long term follow up series have been analysed to confirm its suggested negative prognostic role. This information will be of great clinical impact because, with the exception of the extrathyroidal invasion and lymphnodes metastases, there are no other relevant prognostic factors for MTC patients. A part from RET somatic mutations, no other oncogenes have been found in RET negative cases. However, with the exception of a different outcome, the 2 groups of RET positive and negative MTC seem not to have other major epidemiological and pathological differences.
RET/MEN2 mutations have a gain of function effect. In all cases, the kinase becomes constitutively active with different mechanisms, depending on site of the aminoacidic change. Extracellular mutants display constitutive kinase activity consequent to ligand-independent dimerization. Mechanism of activation of RET by intracellular mutations is less clear. Likely, they modify the structure of the kinase switching on constitutively the enzymatic function. Moreover, for M918T mutant, it has been demonstrated a change of substrate specificity as well. Beyond such frequent mutations, rare RET variants have been identified in MEN2 carriers, and some of those have been shown to have a gain-of-function effect. Nevertheless is not always obvious if and how such mutations can induce RET activation. As the majority of Receptor Tyrosine Kinases, RET switches on the RAS/MAPK and PI3K/AKT transduction pathways, which are involved in mediating RET-dependent cell proliferation, survival and transformation. The question of whether the RET negative MTC are also related to the activation of the RET downstream kinase pathways needs to be answered. Furthermore, if the kinase pathway will result activated also in RET negative cases, other mechanisms of RET activation (i.e gene amplification or mRNA overexpression) could be considered as possible alternative mechanisms.
Advanced and metastatic MTC patients are orphans of therapy. Conventional therapies are ineffective and new strategies are urgently needed. Target therapies will be the future of advanced MTC patients. Several tyrosine kinase inhibitors have been already tested on human cell lines demonstrating the ability to reduce the cell growth rate. Pivotal clinical trials have shown that some TK inhibitors, with a higher affinity for RET protein, has positive effect on treated patients. Further studies are needed to confirm these results and clinical trials enrolling a significant number of MTC patients are mandatory to clarify the possibility to employ these drugs on a large scale and to verify their real clinical benefits. Since all the in vitro studies aimed to explore the efficacy of TK inhibitors have been performed on cell lines with RET activation, either due to RET/PTC [NIH-RET/PTC3] or spontaneous RET point mutations transfection [NIH-MEN2A, NIH-MEN2B], it is still unclear if RET negative MTC cases will also take advantage from this kind of targeted therapy.
New molecular therapies for patients with MTC might be targeted to the control of the NOTCH signaling pathway. Recently, Notch1 has been reported to inhibit cellular proliferation and alter the phenotype in MTC cells. Furthermore, Notch1 expression has been found to be altered in human MTC tumor tissue samples. The Notch family's transmembrane receptors (Notch 1-4) actively control an intracellular signalling pathway involved in cellular differentiation. The receptor interaction with specific ligands (Delta family 1-4 and Serrate/Jagged 1 and 2) maintains the undifferentiated state and the acquisition of an alternative differentiation destiny by the cell receiving the signalling through the activation of a series of transcription factors. Deregulation of Notch signaling has been described in many human cancer cell lines, with a dual role as either a tumor suppressor or oncogene. A better definition of the role of Notch1 in MTC will lead to the possibility to find both other mechanisms of tumoral transformation and new drugs.
While waiting both for the results of clinical trials on the effect of TK inhibitors and new drugs targeted to other pathways, other and more conventional therapeutic strategies need to be explored for MTC patients who require an immediate treatment. Since doxorubicin has been proven to be not effective in MTC patients other chemotherapeutic agents have been explored. Vinorelbine is one of the alternative drugs employed in MTC patients with metastatic disease. The main reason of this choice is the evidence in pivotal studies of some clinical benefits (eg stabilization of the disease in 30% of cases) with very few and well tolerated side effects. An increase of vinorelbine efficacy could be obtained by the combination of this drug with other therapeutic procedure. It has recently been reported that some COX-2 inhibitors may increase the efficacy of doxorubicin by regulation of MDR-1 (Multi Drug Resistence) gene. These studies suggest the possibility to increase the sensitivity of MTC cells to vinorelbine by using COX-2 inhibitors which are currently used for the treatment of osteoartropathy and neoplastic pain. <<<