MON-514 Detection of RAS Mutations and RET/PTC Fusions in Thyroid Cancer Using Microfluidic Digital PCR

Background:

The identification of somatic mutations and gene fusions is crucial for guiding therapeutic decisions in patients with thyroid cancer. Microfluidic digital PCR is currently considered as a technique of choice for highly sensitive detection of gene mutations/fusion. We recently demonstrated that dPCR is a useful tool for detection of BRAFV600E and TERT promoter mutations in thyroid tumors.

Objectives:

This study aimed to determine the analytic and clinical validity of dPCR for detection of RAS mutations and RET/PTC fusions in thyroid cancer tissue.

Material and Methods:

Thyroid tissues from 75 patients with PTCs (58 classical PTC (CPTC) and 17 follicular variant (FVPTC) were used for DNA and RNA extraction. The rare mutation SNP genotyping assays which were multiplexed for detection of mutant and wild type NRASQ61; as well as RET/PTC1 and RET/PTC3 were synthesized by Thermo Fisher Scientific. Digital PCR was performed using a QuantStudio 3D Digital PCR platform. QuantStudio Software was used for relative and quantitative data analysis.

Results:

NRASQ61 was detected in 0/58 CPTC and in 6/17 (35%) FVPTC. The ratios of mutant/total varying from 11.7% to 61.5%. Among patients with FVPTC there were no significant associations between the presence of NRASQ61 and patient’s age, sex, multifocal growth, extra-thyroidal invasion and lymph node metastases. The ratios mutant/total correlated with tumor size in patients harboring NRASQ61. In 23 cases, RET/PTC1 and RET/PTC3 transcripts were examined. RET/PTC1 and RET/PTC3 transcripts were detected in 3 and 1 case, respectively. RET/PTCs were detected in CPTC, but not in FVPTC. RET/PTC positive tumors were characterized by multi-focal patterns of growth, presence of extra-thyroidal invasion, and presence of lymph node metastases (4 of 4 cases with RET/PTC). There were not RET/PTCs positive tumors harboring simultaneously anomalies in RAS oncogene.

Conclusions:

Microfluidic digital PCR allows specific, sensitive and rapid detection of RAS mutations and RET/PTC fusions in thyroid tissue samples. Implementation of dPCR-based assays may facilitate analysis of thyroid tumors and support research in patients with thyroid cancer.

Microfluidic Droplet Digital PCR Is a Powerful Tool for Detection of BRAF and TERT Mutations in Papillary Thyroid Carcinomas

We examined the utility of microfluidic digital PCR (dPCR) for detection of BRAF and TERT mutations in thyroid tumors. DNA extracted from 100 thyroid tumors (10 follicular adenomas, 10 follicular cancers, 5 medullary cancers, and 75 papillary thyroid cancer (PTC) were used for detection of BRAF and TERT mutations. Digital PCRs were performed using rare mutation SNP genotyping assays on QuantStudio 3D platform. In PTCs, BRAFV600E was detected by dPCR and Sanger sequencing in 42/75 (56%) and in 37/75 (49%), respectively. BRAFV600E was not detected in other tumors. The ratio of mutant/total BRAF alleles varied from 4.7% to 47.5%. These ratios were higher in classical PTCs (27.1%) as compared to follicular variant PTCs (9.4%) p = 0.001. In PTCs with and without metastases, the ratios of mutant/total BRAF alleles were 27.6% and 18.4%, respectively, (p = 0.03). In metastatic lesions percentages of mutant/total BRAF alleles were similar to those detected in primary tumors. TERTC228T and TERTC250T were found in two and one cases, respectively, and these tumors concomitantly harbored BRAFV600E. These tumors exhibited gross extra-thyroidal extension, metastases to lymph nodes, and pulmonary metastases (one case). Our results showed that dPCR allows quantitative assessment of druggable targets in PTCs and could be helpful in a molecular-based stratification of prognosis in patients with thyroid cancer.

PKA Activates AMPK Through LKB1 Signaling in Follicular Thyroid Cancer

Thyroid cancer affects about one percent of the population, and has seen rising incidence in recent years. Follicular thyroid cancer (FTC) comprises 10-15% of all thyroid cancers. Although FTC is often localized, it can behave aggressively with hematogenous metastasis, leading to an increased risk of cancer death. We previously described a mouse model for FTC caused by tissue-specific ablation of the Protein Kinase A (PKA) regulatory subunit Prkar1a, either by itself or in combination with knockout of Pten. Loss of Prkar1a causes enhanced activity of PKA, whereas ablation of Pten causes activation of Akt signaling. At the molecular level, these genetic manipulations caused activation of mTOR signaling, which was also observed in human FTC cases. To understand the mechanism by which PKA activates mTOR, we began by studying intracellular kinases known to modulate mTOR function. Although AMP-activated kinase (AMPK) has been characterized as a negative regulator of mTOR activity, our tumor model exhibited activation of both AMPK and mTOR. To understand the mechanism by which AMPK was turned on, we next studied kinases known to cause its phosphorylation. In this paper, we report that PKA leads to AMPK activation through the LKB1 kinase. Although LKB1 has traditionally been considered a tumor suppressor, our data indicates that it may have a complex role in the thyroid gland, where its activation appears to be frequently associated with follicular thyroid carcinoma in both mice and humans.

Metformin Targets Mitochondrial Glycerophosphate Dehydrogenase to Control Rate of Oxidative Phosphorylation and Growth of Thyroid Cancer In Vitro and In Vivo

Purpose: Mitochondrial glycerophosphate dehydrogenase (MGPDH) is the key enzyme connecting oxidative phosphorylation (OXPHOS) and glycolysis as well as a target of the antidiabetic drug metformin in the liver. There are no data on the expression and role of MGPDH as a metformin target in cancer. In this study, we evaluated MGPDH as a potential target of metformin in thyroid cancer and investigated its contribution in thyroid cancer metabolism.Experimental Design: We analyzed MGPDH expression in 253 thyroid cancer and normal tissues by immunostaining and examined its expression and localization in thyroid cancer-derived cell lines (FTC133, BCPAP) by confocal microscopy. The effects of metformin on MGPDH expression were determined by qRT-PCR and Western blot analysis. Seahorse analyzer was utilized to assess the effects of metformin on OXPHOS and glycolysis in thyroid cancer cells. We analyzed the effects of metformin on tumor growth and MGPDH expression in metastatic thyroid cancer mouse models.Results: We show for the first time that MGPDH is overexpressed in thyroid cancer compared with normal thyroid. We demonstrate that MGPDH regulates human thyroid cancer cell growth and OXPHOS rate in vitro Metformin treatment is associated with downregulation of MGPDH expression and inhibition of OXPHOS in thyroid cancer in vitro Cells characterized by high MGPDH expression are more sensitive to OXPHOS-inhibitory effects of metformin in vitro and growth-inhibitory effects of metformin in vitro and in vivoConclusions: Our study established MGPDH as a novel regulator of thyroid cancer growth and metabolism that can be effectively targeted by metformin. Clin Cancer Res; 24(16); 4030-43. ©2018 AACR.

Reduced Retinoblastoma Protein Expression Is Associated with Decreased Patient Survival in Medullary Thyroid Cancer

BACKGROUND

The retinoblastoma (RB) transcriptional corepressor 1 protein functions to slow cell-cycle progression. Inactivation of RB by reduced expression and/or hyperphosphorylation allow for enhanced progression through the cell cycle. Murine models develop medullary thyroid carcinoma (MTC) after generalized loss of RB. However, RB expression in MTC has only been evaluated in a small number of tumors, with differing results. The objective of this study was to determine whether reduced expression of RB and/or overexpression of hyperphosphorylated RB predict MTC aggressive behavior.

METHODS

Formalin-fixed, paraffin-embedded primary thyroid tumors and lymph node metastases from MTC patients were evaluated for calcitonin, RB, and phosphorylated RB (pRB) expression by immunohistochemistry. Two expert pathologists evaluated the slides in a blinded manner, and the immunohistochemistry results were compared to disease-specific survival as a primary endpoint.

RESULTS

Seventy-four MTC samples from 56 patients were analyzed in this study, including 51 primary tumors and 23 lymph node metastases. The median follow-up time was 6.75 years after surgery (range 0.64-24.30 years), and the median primary tumor size was 30 mm (range 6-96 mm). Sixty-six percent of cases were classified as stage IV. RB nuclear expression was diffusely present in 88% of primary tumors and 78% of lymph node metastases. Nuclear pRB expression was present in 22% of primary tumors and 22% of lymph node metastases. On univariate analysis, reduced RB (<75% tumor cell staining) trended with lower MTC-specific survival for primary tumor and metastatic nodes (primary tumor hazard ratio = 3.54 [confidence interval 0.81-15.47], p = 0.08; and lymph node hazard ratio = 4.35 [confidence interval 0.87-21.83], p = 0.05). For primary tumors, multivariable analysis showed that low nuclear RB expression was independently associated with worse disease-specific (p = 0.01) and overall (p = 0.02) survival. pRB levels were not associated with survival for either primary tumor or lymph node metastases.

CONCLUSIONS

Reduced RB expression is associated with decreased patient survival in univariate and multivariable analyses, independent from patient age at surgery or advanced TNM stage. Future studies involving larger MTC patient populations are warranted to determine if lower RB expression levels may serve as a biomarker for aggressive disease in patients with MTC.

Abstract 1001: Expression of cytochrome C oxidase 4 (COX4) in thyroid cancer cells

Background:

Targeting cell metabolism has emerged as a therapeutic strategy for the treatment of cancer. Metabolically active thyroid cancers are resistant to treatment with radioactive iodine. Aberrant expression of genes controlling glycolysis was demonstrated in thyroid cancer cells, but little is known regarding the role of mitochondrial proteins in thyroid carcinogenesis. Cytochrome c oxidase 4 (COX4) plays pivotal roles in oxidative phosphorylation and the cellular response to oxidative stress. COX4 may thus represent a promising therapeutic target.

Objectives:

We examined expression of COX4 in human thyroid tumors and performed functional studies using thyroid cancer cell lines.

Material and Methods

Expression of COX4 was examined by immunostaining in 25 follicular adenomas (FAs), 22 follicular cancers (FTCs), 90 papillary cancers (PTCs) and in 48 samples from normal thyroid tissue. FTC-derived (FTC133) and PTC-derived (BCPAP) cell lines were used to create COX4-deficient cells by lentiviral transfection. The efficiency of COX4 inhibition was examined. Mitochondrial membrane potential was examined by JC-1 staining. DNA-damage signaling was examined after cell exposure to γ radiation (6-18 Gy). We also determined the effects of 2-deoxyglucose (2DG) on viability of thyroid cancer cells with compromised COX4. Caspase-3 and PARP cleavage assays were performed to measure apoptosis.

Results

Positive immunostaining with anti-COX4 was detected in 6/48 (12.5%) normal tissue, 5/20 (25%) FAs, 7/22 (31%) FTCs, and 51/90 (56%) PTCs. The intensity of COX4 immunostaining was significantly higher in thyroid cancers than in either normal thyroid (p = 0.0001) or benign FAs (0.001). COX4 expression was more frequently detected in PTCs than in FTCs (p = 0.03). The mRNA level of COX4 was higher in BCPAP and FTC133 cells compared to normal thyroid. In both cell lines, silencing of COX4 altered intra-cellular distribution of JC-1 staining. In control cells, JC-1 staining was perinuclear, but in COX4-deficient cells it became diffusely cytoplasmic. COX4 silencing affected cell growth and response to γradiation in a cell type specific manner. In BCPAP cells, downregulation of COX4 was associated with inhibition of cell growth, block in G1 phase and inhibition of Cyclin D1. In BCPAP cells, COX4 silencing activated DNA-damage signaling and increased sensitivity to γ radiation. Inhibitor of glycolysis (2DG) was more efficient against COX4-deficient than COX4-expressing BCPAP cells. In FTC133 cells, silencing of COX4 increased the rate of growth and induced expression of Cyclin D1. COX4 silencing did not increase FTC133 cell sensitivity to γradiation nor to treatment with 2DG.

Conclusion

COX4 is implicated in regulation of thyroid cancer cell growth and response to DNA damaging or metabolic treatments. These data suggest that evaluation of COX4 in thyroid cancer could serve as a biomarker of response to treatment with metabolic agents.

Citation Format: Vasyl V. Vasko, Athanasios Bikas, Aneeta Patel, John Costello, Rok Tkavc, Kenneth D. Burman, Kirk Jensen. Expression of cytochrome C oxidase 4 (COX4) in thyroid cancer cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1001.

The expression of translocator protein in human thyroid cancer and its role in the response of thyroid cancer cells to oxidative stress

The translocator protein (TSPO), formerly known as a peripheral benzodiazepine receptor, exerts pro-apoptotic function via regulation of mitochondrial membrane potential. We examined TSPO expression in human thyroid tumors (25 follicular adenomas (FA), 15 follicular cancers (FC), and 70 papillary cancers (PC)). The role of TSPO in the regulation of cell growth, migration, and apoptosis was examined in thyroid cancer cell lines after TSPO knockdown with siRNA and after treatment with TSPO antagonist (PK11195). Compared with normal thyroid, the level of TSPO expression was increased in FA, FC, and PC in 24, 26.6, and 55.7% of cases respectively. Thyroid cancer cell lines demonstrated variable levels of TSPO expression, without specific association with thyroid oncogene mutations. Treatment with inhibitors of PI3K/AKT or MEK/ERK signaling was not associated with changes in TSPO expression. Treatment with histone deacetylase inhibitor (valproic acid) increased TSPO expression in TSPO-deficient cell lines (FTC236 cells). TSPO gene silencing or treatment with PK11195 did not affect thyroid cancer cell growth and migration but prevented depolarization of mitochondrial membranes induced by oxidative stress. Induction of TSPO expression by valproic acid was associated with increased sensitivity of FTC236 to oxidative stress-inducible apoptosis. Overall, we showed that TSPO expression is frequently increased in PC. In vitro data suggested the role of epigenetic mechanism(s) in the regulation of TSPO in thyroid cells. Implication of TSPO in the thyroid cancer cell response to oxidative stress suggested its potential role in the regulation of thyroid cancer cell response to treatment with radioiodine and warrants further investigation.

Group I p21-activated kinases regulate thyroid cancer cell migration and are overexpressed and activated in thyroid cancer invasion

p21-activated kinases (PAKs) are a family of serine/threonine kinases that regulate cytoskeletal dynamics and cell motility. PAKs are subdivided into group I (PAKs 1-3) and group II (PAKs 4-6) on the basis of structural and functional characteristics. Based on prior gene expression data that predicted enhanced PAK signaling in the invasive fronts of aggressive papillary thyroid cancers (PTCs), we hypothesized that PAKs functionally regulate thyroid cancer cell motility and are activated in PTC invasive fronts. We examined PAK isoform expression in six human thyroid cancer cell lines (BCPAP, KTC1, TPC1, FTC133, C643, and SW1746) by quantitative reverse transcription-PCR and western blot. All cell lines expressed PAKs 1-4 and PAK6 mRNA and PAKs 1-4 protein; PAK6 protein was variably expressed. Samples from normal and malignant thyroid tissues also expressed PAKs 1-4 and PAK6 mRNA; transfection with the group I (PAKs 1-3) PAK-specific p21 inhibitory domain molecular inhibitor reduced transwell filter migration by ∼50% without altering viability in all cell lines (P<0.05). BCPAP and FTC133 cells were transfected with PAK1, PAK2, or PAK3-specific small interfering RNA (siRNA); only PAK1 siRNA reduced migration significantly for both cell lines. Immunohistochemical analysis of seven invasive PTCs demonstrated an increase in PAK1 and pPAK immunoactivity in the invasive fronts versus the tumor center. In conclusion, PAK isoforms are expressed in human thyroid tissues and cell lines. PAK1 regulates thyroid cancer cell motility, and PAK1 and pPAK levels are increased in PTC invasive fronts. These data implicate PAKs as regulators of thyroid cancer invasion.

Phase II clinical trial of sorafenib in metastatic medullary thyroid cancer

PURPOSE

Mutations in the RET proto-oncogene and vascular endothelial growth factor receptor (VEGFR) activity are critical in the pathogenesis of medullary thyroid cancer (MTC). Sorafenib, a multikinase inhibitor targeting Ret and VEGFR, showed antitumor activity in preclinical studies of MTC.

PATIENTS AND METHODS

In this phase II trial of sorafenib in patients with advanced MTC, the primary end point was objective response. Secondary end points included toxicity assessment and response correlation with tumor markers, functional imaging, and RET mutations. Using a two-stage design, 16 or 25 patients were to be enrolled onto arms A (hereditary) and B (sporadic). Patients received sorafenib 400 mg orally twice daily.

RESULTS

Of 16 patients treated in arm B, one achieved partial response (PR; 6.3%; 95% CI, 0.2% to 30.2%), 14 had stable disease (SD; 87.5%; 95% CI, 61.7% to 99.5%), and one was nonevaluable. In a post hoc analysis of 10 arm B patients with progressive disease (PD) before study, one patient had PR of 21+ months, four patients had SD >or= 15 months, four patients had SD

CONCLUSION

Sorafenib is reasonably well tolerated, with suggestion of clinical benefit for patients with sporadic MTC. Caution should be taken because of the rare but fatal toxicity potentially associated with sorafenib.

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MESH Headings

• Administration, Oral
• Adult
• Aged
• Benzenesulfonates/administration & dosage
• Benzenesulfonates/adverse effects
• Benzenesulfonates/therapeutic use
• Biomarkers, Tumor/metabolism
• Carcinoma, Medullary/drug therapy
• Carcinoma, Medullary/enzymology
• Carcinoma, Medullary/genetics
• Carcinoma, Medullary/mortality
• Carcinoma, Medullary/secondary
• Disease-Free Survival
• Female
• Humans
• Kaplan-Meier Estimate
• Magnetic Resonance Imaging
• Male
• Middle Aged
• Mutation
• Niacinamide/analogs & derivatives
• Phenylurea Compounds
• Positron-Emission Tomography
• Protein Kinase Inhibitors/administration & dosage
• Protein Kinase Inhibitors/adverse effects
• Protein Kinase Inhibitors/therapeutic use
• Proto-Oncogene Mas
• Proto-Oncogene Proteins c-ret/antagonists & inhibitors
• Proto-Oncogene Proteins c-ret/genetics
• Pyridines/administration & dosage
• Pyridines/adverse effects
• Pyridines/therapeutic use
• Receptors, Vascular Endothelial Growth Factor/antagonists & inhibitors
• Sorafenib
• Thyroid Neoplasms/drug therapy
• Thyroid Neoplasms/enzymology
• Thyroid Neoplasms/genetics
• Thyroid Neoplasms/mortality
• Thyroid Neoplasms/pathology
• Time Factors
• Tomography, X-Ray Computed
• Treatment Outcome
• United States
• Young Adult

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Grants

• N01CM62207 NCI NIH HHS
• N01-CM-62207 NCI NIH HHS

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Abstract 5348: Detection of herpes simplex viruses in thyroid cancer

Introduction: There is limited information about the role of herpesviridae viruses in thyroid cancer.

Materials and Methods: Thyroid tissues from 109 patients with benign (44) and malignant (65) lesions were analyzed for HSV1 and HSV2 DNA. Confirmatory studies included direct sequencing, analysis of viral gene expression and activation of viral-inducible signaling pathways. Expression of viral entry receptor Nectin-1 was examined in human samples and in cancer cell lines. In vitro experiments were performed to explore the molecular mechanisms underlying thyroid cancer cell susceptibility to HSV.

Results: HSV was detected in 43/109 (39.4%) of examined samples. HSV positive tumors were characterized by interferon-beta expression, nuclear NFkB expression and Akt activation. Lymphocytes infiltration and oncocytic cellular features were common in HSV positive tumors. HSV1 was detected with same frequency in benign and malignant thyroid tumors. HSV2 was significantly associated with papillary thyroid cancer and presence of lymph nodes metastases. Nectin-1 expression was increased in thyroid tumors compared to normal thyroid tissue and further increased in papillary thyroid cancer. The level of Nectin-1 expression in cancer cell lines correlated with their susceptibility to HSV. Inhibition of PI3K/AKT or MAPK/ERK signaling did not affect the level of Nectin-1 expression but decreased thyroid cancer cell susceptibility to HSV. Thyroid cancer cell with epithelial-like morphology underwent epithelial to mesenchymal transition after chronic exposure to TNF. Induction of epithelial to mesenchymal transition was associated with increased thyroid cancer cell susceptibility to HSV.

Conclusion. HSV was detected in human thyroid tumors and HSV2 was associated with metastatic thyroid cancers. In vivo and vitro data showed that during tumor progression thyroid cells acquire increased susceptibility to HSV due to 1) increased expression of viral entry mediator Nectin-1; 2) activation of mitogenic signaling and 3) induction of EMT in metastatic cancers.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 5348.

Phase II trial of sorafenib in metastatic thyroid cancer

PURPOSE

Based on the pivotal role of Ras-Raf-MAP-ERK signaling and vascular endothelial growth factor (VEGF) in papillary thyroid cancer (PTC), we conducted a phase II clinical trial of sorafenib targeting RAF and VEGF receptor kinases in PTC.

PATIENTS AND METHODS

The primary end point was the objective response rate. Secondary end points included response correlation with serum thyroglobulin (Tg); functional imaging; tumor genotype; and signaling inhibition in tumor biopsies. Using a Simon minimax two-stage design, 16 or 25 chemotherapy-naïve metastatic PTC patients were to be enrolled in arm A (accessible tumor for biopsy). Arm B patients had other subtypes of thyroid carcinoma or prior chemotherapy, and did not require tumor biopsies. Patients received 400 mg orally twice per day of sorafenib. Response was assessed every 2 months using RECIST (Response Evaluation Criteria in Solid Tumors).

RESULTS

Of 41 PTC patients, six patients had a partial response (PR; 15%; 95% CI, 6 to 29) and 23 patients (56%; 95% CI, 40 to 72) had stable disease longer than 6 months. Median duration of PR was 7.5 months (range, 6 to 14). Median progression-free survival was 15 months (95% CI, 10 to 27.5). In 14 (78%) of 18 Tg-assessable PTC patients, Tg declined more than 25%. Common grade 3 adverse events included hand-foot skin reaction, musculoskeletal pain, and fatigue. BRAF mutation was detected in 17 (77%) of 22 PTCs analyzed. Four of 10 paired tumor biopsies from PTC patients showed a reduction in levels of vascular endothelial growth factor receptor phosphorylation, ERK phosphorylation, and in VEGF expression during sorafenib therapy. No PRs were noted among non-PTC patients.

CONCLUSION

Sorafenib is reasonably well-tolerated therapy with clinical and biologic antitumor activity in metastatic PTC.

Molecular mechanisms involved in differentiated thyroid cancer invasion and metastasis

PURPOSE OF REVIEW

The majority of patients with thyroid cancer have an excellent prognosis, however patients with extensive local invasion and distant metastasis frequently do not respond to standard treatments and have worsened prognosis. Understanding the specific mechanisms involved in thyroid cancer invasion and metastasis is critical in order to develop new treatments specifically targeted for these patients.

RECENT FINDINGS

The genetic basis for thyroid cancer initiation and development is well characterized, with the majority of studies implicating activation of the RAS-RAF-ERK and PI3K/PDK1/Akt signaling pathways. Over the last several years, data from a concerted effort to define the pathways involved in invasion and metastasis suggest that reactivation of embryonic pathways involved in cell movement, to include epithelial to mesenchymal transition and collective cell migration, may be involved in cancer cell migration and invasion. The previously identified thyroid oncogenes, BRAF, RET/PTC and Ras, appear to be important regulators of this process.

SUMMARY

The molecular mechanisms that control cell migration during embryological development, such as epithelial to mesenchymal transition, appear to be reactivated in invading thyroid cancer cells. Elucidation of the signal-transduction networks and molecules that are involved in thyroid cancer invasion may lead to novel therapeutic targets.