piperidines and Carcinoma--Medullary

Medullary thyroid carcinoma (MTC) represents 3-5% of thyroid cancers. 75% is sporadic and 25% is the dominant component of the hereditary multiple endocrine neoplasia (MEN) type 2 syndromes. Three different subtypes of MEN2, such as MEN2A, MEN2B, and Familial MTC (FMTC) have been defined, based on presence or absence of hyperparathyroidism, pheocromocytoma and characteristic clinical features. Mutations of the RET proto-oncogene are implicated in the pathogenesis of MTC, but there are many other mutational patterns involved. In MEN2A, Codon 634 in exon 11 (Cys634Arg), corresponding to a cysteine in the extracellular cysteine-rich domain, is the most commonly altered codon. Many other mutations include codons 611, 618, 620. In the genetical testing of RET mutations in MTCs, Next-Generation Sequencing (NGS) is taking an increasingly important role. One of the most important benefit is the comprehensive analysis of molecular alterations in MTC, which allows rapidly to select patients with different risk levels. There is a difference in miRNA expression pathway between sporadic and hereditary MTCs. Among sporadic cases, expression of miR-127 was significantly lower in those who harbor somatic RET mutations than those with wild-type RET. CDKN1B mutations are associated with many clinical pictures of cancers, such as MEN4. V109G polymorphism is associated with sporadic MTCs negative for RET mutations, and might influence the clinical course of the patients affected by MTC. Although surgery (i.e. total thyroidectomy with neck lymph node dissection) is the elective treatment for MTCs, about 80% of patients have distant metastases at diagnosis and in this cases surgery is not enough and an additional treatment is needed. Interesting results come from two large phase III clinical trials with two targeted tyrosine kinase inhibitors (TKIs), vandetanib and cabozantinib.. New genetical testings and therapeutical approaches open new perspectives in MTC management.

Topics: Anilides; Carcinoma, Medullary; Codon; Exons; Humans; Male; Middle Aged; Multiple Endocrine Neoplasia Type 2a; Mutation; Piperidines; Polymorphism, Genetic; Proto-Oncogene Mas; Proto-Oncogene Proteins c-ret; Pyridines; Quinazolines; Thyroid Neoplasms; Thyroidectomy

To review the place in therapy of vandetanib for medullary thyroid carcinoma (MTC).. Literature searches were performed in Ovid MEDLINE, EMBASE, and Google Scholar using the search terms ZD6474 OR vandetanib OR Caprelsa combined with medullary thyroid carcinoma.. Two phase 2 trials and 1 phase 3 trial were identified.. Vandetanib is approved for the treatment of unresectable, locally advanced or metastatic MTC in patients with symptomatic or progressive disease. In the phase 3 randomized, double-blind, placebo-controlled trial, vandetanib 300 mg daily (n = 231) was compared with placebo (n = 100). Vandetanib-treated patients experienced a significant improvement in progression-free survival (PFS; hazard ratio [HR] = 0.46; 95% CI = 0.31-0.69; P < .001). No difference in overall survival (OS) was seen at the time of publication. Most adverse effects were grade 1 or 2 and managed by dose interruptions or reductions. The most common grade 3/4 adverse effects were diarrhea, hypertension, QT prolongation, fatigue, and rash. Because of the potential for QT prolongation, torsades de pointes, and sudden death, vandetanib is restricted via a Risk Evaluations and Mitigation Strategy program.. Vandetanib prolongs PFS but has not been shown to improve OS. Vandetanib can be considered for patients with unresectable locoregional disease. It is a first-line option for patients with unresectable symptomatic distant metastases as well as an option for advanced disseminated symptomatic metastatic disease. Vandetanib is expected to be an important addition to the formulary of health plans that provide prescription drug benefits.

Topics: Antineoplastic Agents; Carcinoma, Medullary; Carcinoma, Neuroendocrine; Clinical Trials, Phase II as Topic; Clinical Trials, Phase III as Topic; Disease-Free Survival; Drug Interactions; Drug Labeling; Humans; Neoplasm Metastasis; Piperidines; Quinazolines; Randomized Controlled Trials as Topic; Thyroid Neoplasms

Medullary thyroid cancer (MTC) is a rare cancer. Vandetanib, a RET tyrosine-kinase inhibitor, significantly increased progression free survival and is the first treatment approved in France for unresectable, locally advanced or metastatic MTC that is symptomatic or progressive. Most frequents adverse events are diarrhea, folliculitis and asthenia. The prolongation of the QT interval on electrocardiogram is frequent but in the most of cases not clinically relevant. A good selection of the patients who could benefit from this treatment and management of side effect are important for the risk-benefit assessment.

Topics: Antineoplastic Agents; Carcinoma, Medullary; Carcinoma, Neuroendocrine; Humans; Piperidines; Proto-Oncogene Proteins c-ret; Quinazolines; Rare Diseases; Thyroid Neoplasms

Vandetanib is a small molecule tyrosine kinase inhibitor that has been recently approved as an 'orphan drug' for the treatment of patients with unresectable, locally advanced, or metastatic medullary thyroid cancer (MTC).. MTC is a neuroendocrine malignancy frequently associated with mutations to the RET proto-oncogene. Vandetanib selectively targets RET, vascular endothelial growth factor receptor-2, and epidermal growth factor receptor dependent signaling. Vandetanib has been shown to improve progression-free survival in patients with advanced MTC. In general, vandetanib is well tolerated, but QTc prolongation remains a potential concern demanding careful patient selection and monitoring.. Vandetanib has emerged as one of the more promising small molecule tyrosinse kinase inhibitors, providing durable rates of disease stabilization, with an acceptable adverse event profile in patients with advanced MTC.

Topics: Antineoplastic Agents; Carcinoma, Medullary; Clinical Trials as Topic; Humans; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Mas; Quinazolines; Thyroid Neoplasms

The recent availability of molecular targeted therapies leads to a reconsideration of the treatment strategy for patients with distant metastases from medullary thyroid carcinoma. In patients with progressive disease, treatment with kinase inhibitors should be offered.

Topics: Antineoplastic Agents; Carcinoma, Medullary; Carcinoma, Neuroendocrine; Clinical Trials as Topic; Humans; Molecular Targeted Therapy; Patient Selection; Piperidines; Protein Kinase Inhibitors; Quinazolines; Thyroid Neoplasms

Thyroid cancer incidence has significantly increased in the last three decades and many patients seek medical attention for its treatment every year. Among follicular cell-derived tumors, the majority are differentiated thyroid carcinomas (DTC), whose prognosis is very good with only 15% of the cases presenting disease persistence or recurrence after initial treatment. Medullary thyroid carcinoma has a worse prognosis, especially in patients with diffused cancers at the time of initial surgery. Traditional treatment options for persistent or recurrent disease include additional surgery, radioiodine treatment and TSH-suppression in DTC patients; external beam radiotherapy, and cytotoxic chemotherapy, often have low efficacy and many patients with advanced disease ultimately die. In the last two decades many of the molecular events involved in cancer formation have been uncovered. This knowledge has prompted the development of novel therapeutic strategies mainly based on the inhibition of key molecular mediators of the tumorigenic process. In particular the class of small-molecule tyrosine kinase inhibitors was enriched by many compounds that have reached clinical trials and in some cases have had approval for clinical use in specific cancers. Many of these compounds entered clinical trials also for locally advanced or metastatic thyroid carcinomas showing very promising results.

Topics: Antineoplastic Agents; Axitinib; Benzenesulfonates; Carcinoma, Medullary; Carcinoma, Papillary; Humans; Imidazoles; Indazoles; Indoles; Niacinamide; Oligonucleotides; Phenylurea Compounds; Piperidines; Protein Kinase Inhibitors; Pyridines; Pyrroles; Quinazolines; Sorafenib; Sunitinib; Thyroid Neoplasms

Medullary thyroid carcinoma (MTC) is a manifestation of multiple endocrine neoplasia type 2 (MEN2) syndromes caused by germline, activating mutations in the RET (REarranged during Transfection) proto-oncogene. Vandetanib, a VEGF and EGF receptor inhibitor, blocks RET tyrosine kinase activity and is active in adults with hereditary MTC.. We conducted a phase I/II trial of vandetanib for children (5-12 years) and adolescents (13-18 years) with MTC to define a recommended dose and assess antitumor activity. The starting dose was 100 mg/m(2) administered orally, once daily, continuously for 28-day treatment cycles. The dose could be escalated to 150 mg/m(2)/d after two cycles. Radiographic response to vandetanib was quantified using RECIST (v1.0), biomarker response was measured by comparing posttreatment serum calcitonin and carcinoembryonic antigen (CEA) levels to baseline, and a patient-reported outcome was used to assess clinical benefit.. Sixteen patients with locally advanced or metastatic MTC received vandetanib for a median (range) 27 (2-52) cycles. Eleven patients remain on protocol therapy. Diarrhea was the primary dose-limiting toxicity. In subjects with M918T RET germline mutations (n = 15) the confirmed objective partial response rate was 47% (exact 95% confidence intervals, 21%-75%). Biomarker partial response was confirmed for calcitonin in 12 subjects and for CEA in 8 subjects.. Using an innovative trial design and selecting patients based on target gene expression, we conclude that vandetanib 100 mg/m(2)/d is a well-tolerated and highly active new treatment for children and adolescents with MEN2B and locally advanced or metastatic MTC.

Topics: Adolescent; Carcinoma, Medullary; Carcinoma, Neuroendocrine; Child; Child, Preschool; Drug-Related Side Effects and Adverse Reactions; Gene Expression Regulation, Neoplastic; Germ-Line Mutation; Humans; Multiple Endocrine Neoplasia Type 2b; Neoplasm Metastasis; Neoplasm Recurrence, Local; Piperidines; Protein-Tyrosine Kinases; Proto-Oncogene Mas; Proto-Oncogene Proteins c-ret; Quinazolines; Thyroid Neoplasms

PURPOSE There is no effective therapy for patients with distant metastasis of medullary thyroid carcinoma (MTC). Activating mutations in the RET proto-oncogene cause hereditary MTC, which provides a strong therapeutic rationale for targeting RET kinase activity. This open-label, phase II study assessed the efficacy of vandetanib, a selective oral inhibitor of RET, vascular endothelial growth factor receptor, and epidermal growth factor receptor signaling, in patients with advanced hereditary MTC. METHODS Patients with unresectable locally advanced or metastatic hereditary MTC received initial treatment with once-daily oral vandetanib 300 mg. The dose was adjusted additionally in some patients on the basis of observed toxicity until disease progression or any other withdrawal criterion was met. The primary assessment was objective tumor response (by RECIST [Response Evaluation Criteria in Solid Tumors]). Results Thirty patients received initial treatment with vandetanib 300 mg/d. On the basis of investigator assessments, 20% of patients (ie, six of 30 patients) experienced a confirmed partial response (median duration of response at data cutoff, 10.2 months). An additional 53% of patients (ie, 16 of 30 patients) experienced stable disease at >/= 24 weeks, which yielded a disease control rate of 73% (ie, 22 of 30 patients). In 24 patients, serum calcitonin levels showed a 50% or greater decrease from baseline that was maintained for at least 4 weeks; 16 patients showed a similar reduction in serum carcinoembryonic antigen levels. The most common adverse events were diarrhea (70%), rash (67%), fatigue (63%), and nausea (63%). CONCLUSION In this study, vandetanib demonstrated durable objective partial responses and disease control with a manageable adverse event profile. These results demonstrate that vandetanib may provide an effective therapeutic option in patients with advanced hereditary MTC, a rare disease for which there has been no effective therapy.

Topics: Administration, Oral; Adult; Aged; Antineoplastic Agents; Biomarkers, Tumor; Calcitonin; Carcinoembryonic Antigen; Carcinoma, Medullary; Disease-Free Survival; Drug Administration Schedule; Female; France; Genetic Predisposition to Disease; Germ-Line Mutation; Humans; Kaplan-Meier Estimate; Male; Middle Aged; Pedigree; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Mas; Proto-Oncogene Proteins c-ret; Quinazolines; Risk Factors; Thyroid Neoplasms; Time Factors; Treatment Outcome; United States; Young Adult

Vandetanib is a once-daily oral inhibitor of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinases that also inhibits rearranged during transfection kinase activity. Vandetanib (300 mg/d) has previously demonstrated antitumor activity in patients with advanced hereditary medullary thyroid cancer (MTC). This study investigated the efficacy and safety of 100 mg/d vandetanib in patients with advanced hereditary MTC.. Eligible patients with unresectable, measurable, locally advanced, or metastatic hereditary MTC received 100 mg/d vandetanib. Upon disease progression, eligible patients could enter postprogression treatment with 300 mg/d vandetanib until a withdrawal criterion was met. The primary objective was to assess the objective response rate by response evaluation criteria in solid tumors.. The study comprised 19 patients (13 males, six females; mean age 45 yr). Confirmed objective partial responses were observed in three patients, yielding an objective response rate of 16% (95% confidence interval 3.4-39.6). Stable disease lasting 24 wk or longer was reported in a further 10 patients (53%); the disease control rate was therefore 68% (95% confidence interval 43.4-87.4). Serum levels of calcitonin and carcinoembryonic antigen showed a sustained 50% or greater decrease from baseline in 16% (three of 19) and 5% (one of 19) of patients, respectively. Adverse events were predominantly grade 1 or 2 and consistent with previous vandetanib monotherapy studies.. Vandetanib at a once-daily dose of 100 mg has clinically relevant antitumor activity in patients with locally advanced or metastatic hereditary MTC and an overall acceptable safety profile.

Topics: Adult; Aged; Antineoplastic Agents; Calcitonin; Carcinoembryonic Antigen; Carcinoma, Medullary; Codon; Double-Blind Method; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Neoplasm Metastasis; Piperidines; Protein Kinase Inhibitors; Quinazolines; Thyroid Neoplasms; Tomography, X-Ray Computed; Young Adult

Topics: Anilides; Antineoplastic Agents; Carcinoma, Medullary; Drug Approval; Humans; Mutation; Phenylurea Compounds; Piperidines; Precision Medicine; Proto-Oncogene Proteins c-ret; Pyrazoles; Pyridines; Pyrimidines; Quinazolines; Quinolines; Thyroid Cancer, Papillary; Thyroid Neoplasms

Topics: Adolescent; Carcinoma, Medullary; Child; Disease Progression; Disease-Free Survival; Female; Germ-Line Mutation; Humans; Male; Multiple Endocrine Neoplasia Type 2a; Outcome Assessment, Health Care; Piperidines; Protein Kinase Inhibitors; Quinazolines; Thyroid Neoplasms

The advent of multikinase inhibitor (MKI) therapy has led to a radical change in the treatment of patients with advanced thyroid carcinoma. The aim of this manuscript is to communicate rare adverse events that occurred in less than 5% of patients in clinical trials in a subset of patients treated in our hospital.. Out of 760 patients with thyroid cancer followed up with in our Division of Endocrinology, 29 (3.8%) received treatment with MKIs. The median age at diagnosis of these patients was 53 years (range 20-70), and 75.9% of them were women. Sorafenib was prescribed as first-line treatment to 23 patients with differentiated thyroid cancer and as second-line treatment to one patient with advanced medullary thyroid cancer (MTC). Vandetanib was indicated as first-line treatment in 6 patients with MTC and lenvatinib as second-line treatment in two patients with progressive disease under sorafenib treatment.. During the follow-up of treatment (mean 13.7 ± 7 months, median 12 months, range 6-32), 5/29 (17.2%) patients presented rare adverse events. These rare adverse effects were: heart failure, thrombocytopenia, and squamous cell carcinoma during sorafenib therapy and squamous cell carcinoma and oophoritis with intestinal perforation during vandetanib treatment.. About 3 to 5 years after the approval of MKI therapy, we learned that MKIs usually lead to adverse effects in the majority of patients. Although most of them are manageable, we still need to be aware of potentially serious and rare or unreported adverse effects that can be life-threatening.

Topics: Adult; Aged; Antineoplastic Agents; Carcinoma; Carcinoma, Medullary; Female; Follow-Up Studies; Heart Failure; Humans; Intestinal Perforation; Kaplan-Meier Estimate; Male; Middle Aged; Oophoritis; Phenylurea Compounds; Piperidines; Protein Kinase Inhibitors; Quinazolines; Quinolines; Retrospective Studies; Risk Factors; Sorafenib; Thrombocytopenia; Thyroid Neoplasms; Time Factors; Young Adult

Medullary thyroid carcinoma (MTC) occurs sporadically in 75% of patients. Metastatic disease is associated with significantly poorer survival. The aim of this study was to identify prognostic markers for progressive MTC and oncogenic factors associated with response to vandetanib therapy.. Clinical courses of 32 patients with sporadic MTC (n=10 pN0cM0, n=8 pN1cM0, n=14 pN1cM1) were compared with genetic profiles of the patients' primary tumour tissue. Analysis for RET proto-oncogene mutations was performed by Sanger sequencing and next-generation sequencing (NGS). The mRNA expression (mRNA count) of 33 targets was measured by nCounter NanoString analysis.. Somatic RET mutations occurred in 21/32 patients. The RET918 mutation was found in 8/14 pN1cM1 patients. BRAF (P=0.019), FGFR2 (P=0.007), FGFR3 (P=0.044) and VEGFC (P=0.042) mRNA expression was significantly lower in pN1cM0/pN1cM1 compared with pN0cM0 patients, whereas PDGFRA (P=0.026) mRNA expression was significantly higher in pN1cM0/pN1cM1 when compared with pN0cM0 patients. Among the 10/32 vandetanib-treated patients, 5 showed partial response (PR), all harbouring the RET918 mutation. mRNA expression of FLT1 (P=0.039), FLT4 (P=0.025) and VEGFB (P=0.042) was significantly higher in therapy responders.. In this study, we identified molecular markers in primary tumour tissue of sporadic MTC associated with the development of metastasis (both lymph node and organ metastasis) as well as response to vandetanib therapy.

Topics: Adult; Aged; Aged, 80 and over; Antineoplastic Agents; Biomarkers, Tumor; Carcinoma, Medullary; Female; Humans; Male; Middle Aged; Mutation; Piperidines; Prognosis; Protein Kinase Inhibitors; Proto-Oncogene Mas; Proto-Oncogene Proteins c-ret; Quinazolines; Thyroid Neoplasms; Treatment Outcome

Topics: Aged; Biopsy, Needle; Carcinoma, Medullary; Erythema Multiforme; Follow-Up Studies; Humans; Immunohistochemistry; Male; Neoplasm Staging; Photosensitivity Disorders; Piperidines; Quinazolines; Risk Assessment; Thyroid Neoplasms; Thyroidectomy

Oncogenic conversion of the RET tyrosine kinase is a frequent feature of medullary thyroid carcinoma (MTC). ZD6474 (vandetanib) is an ATP-competitive inhibitor of RET, epidermal growth factor receptor (EGFR), and vascular endothelial growth factor receptors kinases. In this study, we have studied ZD6474 mechanism of action in TT and MZ-CRC-1 human MTC cell lines, carrying cysteine 634 to tryptophan (C634W) and methionine 918 to threonine (M918T) RET mutation respectively. ZD6474 blunted MTC cell proliferation and RET, Shc and p44/p42 mitogen-activated protein kinase (MAPK) phosphorylation. Single receptor knockdown by RNA interference showed that MTC cells depended on RET for proliferation. Adoptive expression of the ZD6474-resistant V804M RET mutant rescued proliferation of TT cells under ZD6474 treatment, showing that RET is a key ZD6474 target in these MTC cells. Upon RET inhibition, adoptive stimulation of EGFR partially rescued TT cell proliferation, MAPK signaling, and expression of cell-cycle-related genes. This suggests that simultaneous inhibition of RET and EGFR by ZD6474 may overcome the risk of MTC cells to escape from RET blockade through compensatory over-activation of EGFR.

Topics: Carcinoma, Medullary; Cell Line, Tumor; Cell Proliferation; ErbB Receptors; Humans; Mutation; Piperidines; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-ret; Quinazolines; Signal Transduction; Thyroid Neoplasms; Transforming Growth Factor alpha; Vascular Endothelial Growth Factor Receptor-2

Hereditary medullary thyroid carcinoma (MTC) is caused by germline mutations in the RET proto-oncogene, resulting in constitutive activation of the RET tyrosine kinase. A substantial proportion of sporadic MTCs also have RET mutations, making the RET tyrosine kinase a potential therapeutic target in MTC. We have established a transplantable MTC in nude mice from a sporadic human MTC carrying a RET C634R mutation. Transplanted tumors had an exponential growth rate with an approximate doubling time of about 3 weeks, and expressed a neuroendocrine phenotype characteristic of MTC, e.g., expression of calcitonin, chromogranin A (CgA), synaptophysin, synaptic vesicle protein 2 (SV2), vesicular monoamine transporter-1 and -2, carcinoembryonic antigen, cytokeratin 8/18, epithelial cadherin, and neural cell adhesion molecule. Plasma calcitonin and CgA levels were elevated in tumor-bearing mice and correlated with tumor size. Cytogenetic analysis, including spectral karyotyping, confirmed the human origin of the xenografted tumors and demonstrated an abnormal, near triploid karyotype. Treatment of tumor-bearing nude mice with the tyrosine kinase inhibitor ZD6474, which specifically inhibits RET, epidermal growth factor receptor (EGFR), and vascular endothelium growth factor receptor (VEGFR) tyrosine kinases, resulted in a dose-dependent inhibition of tumor growth. Oral ZD6474 given once daily (250 mg/kg, 5 days/week) reduced tumor volume to 11% when compared with controls after 4 weeks. Our results show that this transplantable MTC, designated GOT2, represents a novel and useful model for studies of MTC and RET tyrosine kinase-dependent tumor growth.

Topics: Aged; Animals; Calcitonin; Carcinoma, Medullary; Cell Line, Tumor; Cell Transformation, Neoplastic; Chromogranin A; Disease Models, Animal; ErbB Receptors; Humans; Karyotyping; Male; Mice; Mice, Nude; Mutation; Piperidines; Protein Kinase Inhibitors; Protein-Tyrosine Kinases; Proto-Oncogene Mas; Proto-Oncogene Proteins c-ret; Quinazolines; Thyroid Neoplasms; Vascular Endothelial Growth Factor Receptor-1; Xenograft Model Antitumor Assays

We have recently demonstrated that the pyrazolopyrimidines PP1 and PP2 and the 4-anilinoquinazoline ZD6474 display a strong inhibitory activity (IC(50)< or =100 nM) towards constitutively active oncogenic RET kinases. Here, we show that most oncogenic MEN2-associated RET kinase mutants are highly susceptible to PP1, PP2 and ZD6474 inhibition. In contrast, MEN2-associated swap of bulky hydrophobic leucine or methionine residues for valine 804 in the RET kinase domain causes resistance to the three compounds. Substitution of valine 804 with the small amino- acid glycine renders the RET kinase even more susceptible to inhibition (ZD6474 IC(50): 20 nM) than the wild-type kinase. Our data identify valine 804 of RET as a structural determinant mediating resistance to pyrazolopyrimidines and 4-anilinoquinazolines.

Topics: Carcinoma, Medullary; Catalytic Domain; Cell Line; Drug Resistance; Enzyme Inhibitors; Mitogens; Piperidines; Point Mutation; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-ret; Pyrazoles; Pyrimidines; Quinazolines; Receptor Protein-Tyrosine Kinases; Signal Transduction; Thyroid Neoplasms; Valine

The RET gene is frequently mutated in papillary thyroid carcinoma and in medullary thyroid carcinoma. We have identified three different anti-RET drugs: two pyrazolo-pyrimidines, PP1 and PP2 and an anilinoquinazoline, ZD6474 (AstraZeneca). These compounds are able to inhibit RET kinase activity in vitro (IC50 dose 100 nM) and in vivo and they can prevent RET mediated transformation. Finally, mutation of RET V804 to methionine or leucine, found in MTC patients, induces resistance to the three drugs.

Topics: Carcinoma, Medullary; Carcinoma, Papillary; Dose-Response Relationship, Drug; Drug Administration Schedule; Female; Humans; Male; Mutation; Piperidines; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-ret; Quinazolines; Receptor Protein-Tyrosine Kinases; Sensitivity and Specificity; Thyroid Neoplasms; Treatment Outcome

Multidrug resistance was investigated in TT cells, a human medullary thyroid carcinoma (MTC) cell line and in normal thyrocytes. MDR1 mRNA was revealed by polymerase chain reaction (PCR) analysis both in normal and neoplastic cells despite the absence of glycoprotein P (Pgp) by immunohistochemistry using JSB-1 monoclonal antibody. Glutathione-S-transferase mRNA was undetectable by Northern blotting in TT cells. Doxorubicin-induced cytotoxicity was evaluated in TT cells with MTT, lacticodehydrogenase (LDH), glutathione (GSH) assays and neutral red uptake. IC50 values obtained for MTT assays were higher than those obtained with the three other tests. Cyclosporin A (CSA) (3 microM), verapamil (10 microM) and S9788 (5 microM) partially reversed the resistance to doxorubicin after a 48 h co-incubation (followed by a 24 h post-incubation for the S9788). Under these conditions, GSH levels were altered by verapamil and S9788, whereas CSA decreased LDH activity. CSA and verapamil had no effect on MTT assay. In conclusion this MTC cell line exhibited over-expression of the MDR1 gene and its resistance to doxorubicin can be partially reversed by CSA, verapamil and S9788.

Topics: ATP Binding Cassette Transporter, Subfamily B, Member 1; Carcinoma, Medullary; Cyclosporine; Doxorubicin; Drug Resistance, Multiple; Drug Synergism; Glutathione; Glutathione Transferase; Humans; Neoplasm Proteins; Piperidines; Polymerase Chain Reaction; RNA, Messenger; RNA, Neoplasm; Thyroid Neoplasms; Triazines; Verapamil