Combined deletion of cathepsin protease family members reveals compensatory mechanisms in cancer.

Proteases are important for regulating multiple tumorigenic processes, including angiogenesis, tumor growth, and invasion. Elevated protease expression is associated with poor patient prognosis across numerous tumor types. Several multigene protease families have been implicated in cancer, including cysteine cathepsins. However, whether individual family members have unique roles or are functionally redundant remains poorly understood. Here we demonstrate stage-dependent effects of simultaneously deleting cathepsin B (CtsB) and CtsS in a murine pancreatic neuroendocrine tumor model. Early in tumorigenesis, the double knockout results in an additive reduction in angiogenic switching, whereas at late stages, several tumorigenic phenotypes are unexpectedly restored to wild-type levels. We identified CtsZ, which is predominantly supplied by tumor-associated macrophages, as the compensatory protease that regulates the acquired tumor-promoting functions of lesions deficient in both CtsB and CtsS. Thus, deletion of multiple cathepsins can lead to stage-dependent, compensatory mechanisms in the tumor microenvironment, which has potential implications for the clinical consideration of selective versus pan-family cathepsin inhibitors in cancer.

Histone demethylase PHF8 drives neuroendocrine prostate cancer progression by epigenetically upregulating FOXA2.

Neuroendocrine prostate cancer (NEPC) is a more aggressive subtype of castration-resistant prostate cancer (CRPC). Although it is well established that PHF8 can enhance prostate cancer cell proliferation, whether PHF8 is involved in prostate cancer initiation and progression is relatively unclear. By comparing the transgenic adenocarcinoma of the mouse prostate (TRAMP) mice with or without Phf8 knockout, we systemically examined the role of PHF8 in prostate cancer development. We found that PHF8 plays a minimum role in initiation and progression of adenocarcinoma. However, PHF8 is essential for NEPC because not only is PHF8 highly expressed in NEPC but also animals without Phf8 failed to develop NEPC. Mechanistically, PHF8 transcriptionally upregulates FOXA2 by demethylating and removing the repressive histone markers on the promoter region of the FOXA2 gene, and the upregulated FOXA2 subsequently regulates the expression of genes involved in NEPC development. Since both PHF8 and FOXA2 are highly expressed in NEPC tissues from patients or patient-derived xenografts, the levels of PHF8 and FOXA2 can either individually or in combination serve as NEPC biomarkers and targeting either PHF8 or FOXA2 could be potential therapeutic strategies for NEPC treatment. © 2020 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Phase II study of temozolomide monotherapy in patients with extrapulmonary neuroendocrine carcinoma.

Extrapulmonary neuroendocrine carcinoma (EPNEC) is a lethal disease with a poor prognosis. Platinum-based chemotherapy is used as the standard first-line treatment for unresectable EPNEC. Several retrospective studies have reported the results of the utilization of temozolomide (TMZ) as a drug for the second-line treatment for EPNEC. Patients with unresectable EPNEC that were resistant to platinum-based combination chemotherapy were recruited for a prospective phase II study of TMZ monotherapy. A 200 mg/m2 dose of TMZ was given from day 1 to day 5, every 4 weeks. Response rate (RR) was evaluated as the primary end-point. The presence of O6 -methylguanine DNA methyltransferase (MGMT) in EPNEC patients was also evaluated as exploratory research. Thirteen patients were enrolled in this study. Primary lesions were pancreas (n = 3), stomach (n = 3), duodenum (n = 1), colon (n = 1), gallbladder (n = 1), liver (n = 1), uterus (n = 1), bladder (n = 1), and primary unknown (n = 1). Each case was defined as pathological poorly differentiated neuroendocrine carcinoma from surgically resected and/or biopsied specimens. The median Ki-67 labeling index was 60% (range, 22%-90%). The RR was 15.4%, progression-free survival was 1.8 months (95% confidence interval [CI], 1.0-2.7), overall survival (OS) was 7.8 months (95% CI, 6.0-9.5), and OS from first-line treatment was 19.2 months (95% CI, 15.1-23.3). No grade 3 or 4 hematological toxicity had occurred and there was one case of grade 3 nausea. One case presented MGMT deficiency and this case showed partial response. Temozolomide monotherapy is a feasible, modestly effective, and safe treatment for patients with unresectable EPNEC following platinum-based chemotherapy, especially those with MGMT deficiency.

Integrated computational and Drosophila cancer model platform captures previously unappreciated chemicals perturbing a kinase network.

Drosophila provides an inexpensive and quantitative platform for measuring whole animal drug response. A complementary approach is virtual screening, where chemical libraries can be efficiently screened against protein target(s). Here, we present a unique discovery platform integrating structure-based modeling with Drosophila biology and organic synthesis. We demonstrate this platform by developing chemicals targeting a Drosophila model of Medullary Thyroid Cancer (MTC) characterized by a transformation network activated by oncogenic dRetM955T. Structural models for kinases relevant to MTC were generated for virtual screening to identify unique preliminary hits that suppressed dRetM955T-induced transformation. We then combined features from our hits with those of known inhibitors to create a 'hybrid' molecule with improved suppression of dRetM955T transformation. Our platform provides a framework to efficiently explore novel kinase inhibitors outside of explored inhibitor chemical space that are effective in inhibiting cancer networks while minimizing whole body toxicity.

A case of a primary lung cancer comprised of adenocarcinoma and atypical carcinoid tumor with both components harboring BRAF p.V600E mutation.

Mixed morphology lung tumors are rare; this is the second report of a combined NSCLC and atypical carcinoid tumor. Next generation sequencing was performed on both histologically distinct patterns which identified that both components harbored a BRAF p.V600E mutation. Molecular studies inform our knowledge of the biology and aid in treatment decisions for mixed morphology lung cancers.

New Treatment of Medullary and Papillary Human Thyroid Cancer: Biological Effects of Hyaluronic Acid Hydrogel Loaded With Quercetin Alone or in Combination to an Inhibitor of Aurora Kinase.

The aim of this paper is based on the use of a hyaluronic acid hydrogel of Quercetin tested alone and in combination to an inhibitor of Aurora Kinase type A and B (SNS-314) on human medullary and papillary thyroid cancer cells. Biological investigations were focused on the cellular uptake of the hydrogel, cell viability, antioxidant, and cytokines secretion studies. Quercetin delivered from hydrogel show a time and CD44 dependent interaction with both cell lines with significant anti-inflammatory effects. Combination of Quercetin and SNS-314 leads to a synergistic cytotoxic effect on medullary TT and papillary BCPAP cell lines with a significant reduction of the IC50 value. These results, highlights the importance of synergistic effect of the hyaluronic acid hydrogel of Quercetin with SNS-314 in the regulation of human thyroid cancer cell proliferation and emphasize the anti-tumor activity of these molecules. J. Cell. Physiol. 231: 1784-1795, 2016. © 2015 Wiley Periodicals, Inc.

Use of Tyrosine Kinase Inhibitors for Treatment of Medullary Thyroid Carcinoma.

Two independent events--the identification of activating mutations of the RET proto-oncogene, a receptor tyrosine kinase, in medullary thyroid carcinoma, and the recognition that small organic molecules could bind to and inhibit phosphorylation of signaling molecules, thereby inactivating the pathway-led to the recognition that kinase inhibitors could be used to treat medullary thyroid carcinoma (MTC). The introduction of these compounds into clinical practice has transformed the treatment of metastatic MTC and provided insight into the mechanisms by which RET causes C-cell transformation. This chapter will review the progress in this field over the past 7 years.

Targeting the PI3K/mTOR pathway in murine endocrine cell lines: in vitro and in vivo effects on tumor cell growth.

The mammalian target of rapamycin (mTOR) inhibitors, such as rapalogues, are a promising new tool for the treatment of metastatic gastroenteropancreatic endocrine tumors. However, their mechanisms of action remain to be established. We used two murine intestinal endocrine tumoral cell lines, STC-1 and GLUTag, to evaluate the antitumor effects of rapamycin in vitro and in vivo in a preclinical model of liver endocrine metastases. In vitro, rapamycin inhibited the proliferation of cells in the basal state and after stimulation by insulin-like growth factor-1. Simultaneously, p70S6 kinase and 4EBP1 phosphorylation was inhibited. In vivo, rapamycin substantially inhibited the intrahepatic growth of STC-1 cells, irrespectively of the timing of its administration and even when the treatment was administered after cell intrahepatic engraftment. In addition, treated animals had significantly prolonged survival (mean survival time: 47.7 days in treated animals versus 31.8 days in controls) and better clinical status. Rapamycin treatment was associated with a significant decrease in mitotic index and in intratumoral vascular density within STC-1 tumors. Furthermore, the antitumoral effect obtained after treatment with a combination of rapamycin and phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 was more significant than with rapamycin alone in both cell lines. Our results suggest that the antitumor efficacy of rapamycin in neuroendocrine tumors results from a combination of antiproliferative and antiangiogenic effects. Interestingly, a more potent antitumor efficiency could be obtained by simultaneously targeting several levels of the PI3K/mTOR pathway.

[Correlation Analysis of Serum LDH Concentration before and after Operation and Prognosis of Large Cell Neuroendocrine Lung Cancer Patients].

BACKGROUND: Studies have shown that elevated serum lactate dehydrogenase (LDH) concentration can lead to poor prognosis in patients with small cell lung cancer and lung adenocarcinoma, but its relationship with the prognosis of patients with lung large-cell neuroendocrine carcinoma (L-LCNEC) is not clear. This study aims to explore the influence of L-LCNEC preoperative serum LDH concentration and postoperative LDH concentration change trend on the disease-free survival (DFS) of patients after surgery, so as to judge the clinical prognosis of L-LCNEC provides new ideas. METHODS: Collected the clinical data. The receiver operating characteristic (ROC) curve was used to determine the optimal cut-off value, while the Kaplan-Meier and Cox proportional hazard model were used to analyze data. RESULTS: DFS was shortened in patients with high serum LDH concentration before operation and increased LDH concentration after operation (P<0.001, P<0.001). The preoperative LDH concentration and postoperative LDH concentration change trend were independent prognostic factors for patients (P<0.001, P=0.037). CONCLUSIONS: Preoperative LDH concentration and its postoperative concentration change trend in patients with L-LCNEC are independent prognostic factors for DFS of patients.

Applicability of pan-TRK immunohistochemistry for identification of NTRK fusions in lung carcinoma.

In the last two decades, various therapies have been introduced for lung carcinoma patients, including tyrosine-kinase inhibitors for different mutations. While some of them are specific to specific tumor types, others, like NTRK1-3 fusions, are found in various solid tumors. The occurrence of an NTRK1,2 or 3 fusion acts as a biomarker for efficient treatment with NTRK inhibitors, irrespectively of the tumor type. However, the occurrence of the NTRK1-3 fusions in lung carcinomas is extremely rare. We performed a retrospective analysis to evaluate the applicability of immunohistochemistry with the pan-TRK antibody in the detection of NTRK fusions in lung carcinomas. The study cohort included 176 adenocarcinomas (AC), 161 squamous cell carcinomas (SCC), 31 large-cell neuroendocrine carcinomas (LCNEC), and 19 small cell lung carcinomas (SCLC). Immunohistochemistry (IHC) was performed using the pan-TRK antibody (clone EPR17341, Ventana) on tissue microarrays, while confirmation for all positive cases was done using RNA-based Archer FusionPlex MUG Lung Panel. On IHC staining, 12/387 samples (3.1%) demonstrated a positive reaction. Ten SCC cases (10/161, 6.2%), and two LCNEC cases (2/31, 6.5%) were positive. Positive cases demonstrated heterogeneous staining of tumor cells, mostly membranous with some cytoplasmic and in one case nuclear pattern. RNA-based sequencing did not demonstrate any NTRK1-3 fusion in our patients' collective. Our study demonstrates that pan-TRK expression in lung carcinoma is very low across different histologic types. NTRK1-3 fusions using an RNA-based sequencing approached could not be detected. This stresses the importance of confirmation of immunohistochemistry results by molecular methods.

High-grade neuroendocrine carcinoma of the lung shows increased thymidylate synthase expression compared to other histotypes.

BACKGROUND: Thymidylate synthase (TS) expression has been reported in various tumors, including non-small-cell lung carcinoma (NSCLC), but not in high-grade neuroendocrine (HGNE) carcinoma of the lung. METHODS: We measured TS expression in surgically resected pulmonary tumors, comparing HGNE carcinomas of the lung (13 large-cell neuroendocrine carcinomas, 8 small-cell lung carcinomas) with squamous cell carcinoma and adenocarcinoma of the lung using laser-capture microdissection for tissue isolation, real-time polymerase chain reaction (PCR), and immunohistochemistry. We also measured TS mRNA expression in small-cell lung carcinoma (SCLC) and NSCLC cell lines using real-time PCR. RESULTS: At both mRNA and protein levels, TS expression was significantly higher in squamous cell carcinoma compared to adenocarcinoma. Moreover, TS expression was significantly higher in HGNE carcinomas of the lung compared to squamous cell carcinoma. A significant correlation was found between mRNA and protein expression. TS mRNA expression in SCLC cell lines was significantly higher than in NSCLC cell lines. CONCLUSIONS: TS expression was higher in HGNE carcinomas of the lung than in squamous cell carcinoma, which was higher than in adenocarcinoma. This information may be useful in predicting the effects of TS-inhibiting agents in patients with NSCLC and HGNE carcinomas of the lung.

Increased therapeutic effect on medullary thyroid cancer using a combination of radiation and tyrosine kinase inhibitors.

Since patients with medullary thyroid cancer (MTC) often have metastatic disease at the time of diagnosis, the development of efficient systemic treatment options for MTC is important. Vandetanib and cabozantinib are two tyrosine kinase inhibitors (TKIs) that were recently approved by FDA and EMA for systemic treatment of metastatic MTC. Additionally, since MTC is of a neuroendocrine tumour type, treatment with radiolabelled somatostatin analogues (e.g. 177Lu-octreotate) is a valid option for patients with MTC. The aim of this study was to investigate the potentially increased therapeutic effect of combining radiation therapy with these TKIs for treatment of MTC in a mouse model. Nude mice carrying patient-derived MTC tumours (GOT2) were treated with external beam radiotherapy (EBRT) and/or one of the two TKIs vandetanib or cabozantinib. The tumour volume was determined and compared with that of mock-treated controls. The treatment doses were chosen to give a moderate effect as monotherapy to be able to detect any increased therapeutic effect from the combination therapy. At the end of follow-up, tumours were processed for immunohistochemical (IHC) analyses. The animals in the combination therapy groups showed the largest reduction in tumour volume and the longest time to tumour progression. Two weeks after start of treatment, the tumour volume for these mice was reduced by about 70-75% compared with controls. Furthermore, also EBRT and TKI monotherapy resulted in a clear anti-tumour effect with a reduced tumour growth compared with controls. The results show that an increased therapeutic effect could be achieved when irradiation is combined with TKIs for treatment of MTC. Future studies should evaluate the potential of using 177Lu-octreotate therapy in combination with TKIs in patients.

RABL6A inhibits tumor-suppressive PP2A/AKT signaling to drive pancreatic neuroendocrine tumor growth.

Hyperactivated AKT/mTOR signaling is a hallmark of pancreatic neuroendocrine tumors (PNETs). Drugs targeting this pathway are used clinically, but tumor resistance invariably develops. A better understanding of factors regulating AKT/mTOR signaling and PNET pathogenesis is needed to improve current therapies. We discovered that RABL6A, a new oncogenic driver of PNET proliferation, is required for AKT activity. Silencing RABL6A caused PNET cell-cycle arrest that coincided with selective loss of AKT-S473 (not T308) phosphorylation and AKT/mTOR inactivation. Restoration of AKT phosphorylation rescued the G1 phase block triggered by RABL6A silencing. Mechanistically, loss of AKT-S473 phosphorylation in RABL6A-depleted cells was the result of increased protein phosphatase 2A (PP2A) activity. Inhibition of PP2A restored phosphorylation of AKT-S473 in RABL6A-depleted cells, whereas PP2A reactivation using a specific small-molecule activator of PP2A (SMAP) abolished that phosphorylation. Moreover, SMAP treatment effectively killed PNET cells in a RABL6A-dependent manner and suppressed PNET growth in vivo. The present work identifies RABL6A as a new inhibitor of the PP2A tumor suppressor and an essential activator of AKT in PNET cells. Our findings offer what we believe is a novel strategy of PP2A reactivation for treatment of PNETs as well as other human cancers driven by RABL6A overexpression and PP2A inactivation.

Cystathione ß-Synthase Is Increased in Thyroid Malignancies.

BACKGROUND: Cystathione ß-synthase (CBS) catalyzes the conversion of homocysteine and cysteine to hydrogen sulfide (H2S) and cystathione, via the trans-sulfuration pathway. CBS protein expression levels are increased in several different human malignancies, with increased protein expression correlating with parameters such as tumor stage, anaplasia, metastases, and chemotherapy resistance. MATERIALS AND METHODS: This study employed tissue microarrays to examine CBS expression in benign thyroid tissue, thyroid oncocytomas, thyroid follicular adenomas, and in follicular, papillary, anaplastic, and medullary thyroid carcinomas. RESULTS: CBS expression was increased in all thyroid carcinomas types compared to benign thyroid tissue, but not in thyroid follicular adenomas or oncocytomas. A similar pattern was observed for nicotinamide phosphoribosyltransferase (NAMPT) tissue microarray analysis comparing thyroid adenomas and follicular carcinomas. CONCLUSION: For the first time, we showed that an H2S-syntheszing enzyme plays a role in thyroid malignancies. Additionally, our data suggest that CBS and NAMPT immunohistochemistry may be useful in differentiating follicular adenomas from follicular carcinomas.

Selective Actionable and Druggable Protein Kinases Drive the Progression of Neuroendocrine Prostate Cancer.

Current clinical anti-androgen therapies in advanced prostate cancer (PCa) are driving an increased incidence of neuroendocrine prostate cancer (NEPC), a histological variant exhibiting reduced androgen receptor levels and expression of neuroendocrine markers. The mechanisms underlying the development of NEPC are poorly understood. A set of available data from a well-validated xenograft model of NEPC was used to analyze the exact role of protein kinase (PK) played in the development of NEPC. Fifty-four actionable and druggable PKs, mainly enriched in PI3K-Akt, mTOR, and MAPK signaling pathways, were screened out from the drastically changed PKs during NEPC transdifferentiation. Further analysis based on the crosstalk of these above signaling pathways finally singled out 10 PKs considered drivers and therapeutic targets in the development and treatment of NEPC. In vitro, the variation trend of PK expression observed during NEPC transdifferentiation could be recapitulated in PCa cell lines with different malignant degree. The predicted kinase targets exhibited different sensibilities in the restriction of PC3 cell growth. Selective actionable and druggable PKs may act as drivers in the progression of NEPC, and most of them can be used as potential therapeutic targets in clinical practice.

Evaluation of miRNAs expression in medullary thyroid carcinoma tissue samples: miR-34a and miR-144 as promising overexpressed markers in MTC.

Medullary thyroid carcinoma (MTC) is a rare neoplasia derived from neural parafollicular C cells. MicroRNAs (miRNAs) are small regulatory RNAs with essential roles in the biology of cancers such as MTC and can be applied as diagnostic markers. According to previous studies, miR-144 and miR-34 and their two oncogenes target, mammalian target of rapamycin (mTOR) and AXL receptor tyrosine kinase (AXL), were selected for further investigations in our study. Thirty MTC samples as well as thirty adjacent normal thyroid tissues were applied in this study including 28 formalin-fixed, paraffin-embedded (FFPE) and 2 fresh-frozen MTC samples. RNA extraction and complementary DNA (cDNA) synthesis were performed for all samples. After primer pairs and probes were designed, real-time polymerase chain reaction (real-time PCR) method was used, and the results were analyzed using 2-ΔΔCt method. Receiver operating characteristic (ROC) curve analysis was applied to assess the diagnostic value of the two miRNAs. AXL protein level was measured in all clinical samples using enzyme-linked immunosorbent assay (ELISA) method. Both miRNAs were up-regulated in all clinical samples compared to the normal tissues. AXL was up-regulated in most clinical samples while mTOR was down-regulated in most samples. Furthermore, the level of AXL protein increased. ROC curve analysis demonstrated that increased expression of miR-34a and miR-144 in MTC patients had significant predictive value. The results demonstrated that high expression of miR-144 and miR-34a can be considered as biomarkers of MTC. However, there was no statistically significant correlation between the expression of these miRNAs and target genes in MTC clinical samples.

Telomere length, telomerase activity, and expressions of human telomerase mRNA component (hTERC) and human telomerase reverse transcriptase (hTERT) mRNA in pulmonary neuroendocrine tumors.

BACKGROUND: Telomeres are important for chromosome structure and function, protecting them against degradation. However, few studies have examined telomeres in pulmonary neuroendocrine (NE) tumors. METHODS: We investigated deparaffinized sections obtained from 70 primary NE lung tumors [34 typical carcinoids (TCs), 10 atypical carcinoids (ACs), 16 large cell neuroendocrine carcinoma (LCNECs) and 10 small cell lung carcinomas (SCLCs)]. RESULTS: Positive expressions of human telomerase mRNA component (hTERC) and human telomerase reverse transcriptase (hTERT) mRNA were recognized, respectively, in 58% and 74% of TCs, and in 100% and 100% of ACs, LCNECs and SCLCs. Alteration of telomere length was greater in both LCNECs and SCLCs than in TCs. Telomerase activity was detected in LCNECs, but not in TCs. By the reverse-transcriptase polymerase chain reaction (RT-PCR), hTERC mRNA was detected in 100% of LCNECs and TCs examined, while hTERT mRNA was detected in 67% of LCNECs, but not at all in TCs. CONCLUSIONS: These results suggest that alterations in telomere length, telomerase activity, and the expression of hTERT mRNA may (i) play roles in pathogenesis in pulmonary neuroendocrine tumors, and (ii) be a useful tool for differential diagnosis between TCs and LCNECs.

Role of chemotherapy and the receptor tyrosine kinases KIT, PDGFRalpha, PDGFRbeta, and Met in large-cell neuroendocrine carcinoma of the lung.

PURPOSE: Pulmonary large-cell neuroendocrine carcinoma (LCNEC) is a relatively uncommon, high-grade neuroendocrine tumor sharing several features with small-cell lung carcinoma (SCLC) but currently considered as a variant of non-SCLC and accordingly treated with poor results. Little is known about the optimal therapy of LCNEC and the possible therapeutic molecular targets. PATIENTS AND METHODS: We reviewed 83 patients with pure pulmonary LCNEC to investigate their clinicopathologic features, therapeutic strategy, and immunohistochemical expression and the mutational status of the receptor tyrosine kinases (RTKs) KIT, PDGFRalpha, PDGFRbeta, and Met. RESULTS: LCNEC histology predicted a dismal outcome (overall median survival, 17 months) even in stage I patients (5-year survival rate, 33%). LCNEC strongly expressed RTKs (KIT in 62.7% of patients, PDGFRalpha in 60.2%, PDGFRbeta in 81.9%, and Met in 47%), but no mutations were detected in the exons encoding for the relevant juxtamembrane domains. Tumor stage and size (> or = 3 cm) and Met expression were significantly correlated with survival. At univariate and multivariate analysis, SCLC-based chemotherapy (platinum-etoposide) was the most important variable correlating with survival, both in the adjuvant and metastatic settings (P < .0001). CONCLUSION: Pulmonary LCNEC represents an aggressive tumor requiring multimodal treatment even for resectable stage I disease, and LCNEC seems to respond to adjuvant platinum-etoposide-based chemotherapy. Patients who received this therapy had the best survival rate. Despite our failure in finding mutational events in the tested RTKs, the strong expression of KIT, PDGFRalpha, PDGFRbeta, and Met in tumor cells suggests an important role of these RTKs in LCNEC, and these RTKs seem to be attractive therapeutic targets.

Sorafenib for the Treatment of Progressive Metastatic Medullary Thyroid Cancer: Efficacy and Safety Analysis.

BACKGROUND: Treatment of advanced medullary thyroid carcinoma (MTC) was recently improved with the approval of vandetanib and cabozantinib. However, there is still a need to explore sequential therapy with more than one tyrosine kinase inhibitor (TKI) and to explore alternative therapies when vandetanib and cabozantinib are not available. This study reports the authors' experience with sorafenib as a treatment for advanced MTC. METHODS: This is a retrospective longitudinal study of 13 patients with progressive metastatic MTC treated with sorafenib 400 mg twice daily between December 2011 and January 2015. The primary endpoints were to evaluate response and progression-free survival (PFS) in patients treated with sorafenib outside a clinical trial. The secondary endpoint was an assessment of the toxicity profile. One patient was excluded because of a serious allergic skin rash one week after starting sorafenib. RESULTS: The analysis included 12 patients with metastatic MTC (median age 48 years), 10 with sporadic and 2 with hereditary disease. The median duration of treatment was 11 months, and the median follow-up was 15.5 months. At data cutoff, 2/12 (16%) patients were still on treatment for 16 and 34 months. According to Response Evaluation Criteria in Solid Tumors analysis, 10 (83.3%) patients showed stable disease, and two (16.6%) had progression of disease; no partial response was observed. The median PFS was nine months. However, three patients with extensive and rapidly progressive disease died within three months of sorafenib treatment. The median PFS excluding these three patients was 12 months. Adverse events (AE) occurred in nine (75%) patients. The main AEs were skin toxicity, weight loss, and fatigue. Five (41.6%) patients needed dose reduction, and one patient discontinued treatment because of toxicity. CONCLUSIONS: Treatment with sorafenib in progressive metastatic MTC is well tolerated and resulted in disease control and durable clinical benefit in 75% of patients. Sorafenib treatment could be considered when vandetanib and cabozantinib are not available or after failing these drugs.