BRAFV600E Mutated Thyroid Cancer Research Articles

Combination of Dabrafenib and Trametinib in Patients with Metastatic BRAFV600E-Mutated Thyroid Cancer.

BRAF mutations are detected in 30%-80% of papillary thyroid cancer (PTC) cases. DaBRAFenib and trametinib showed promising antitumor activity in patients with BRAFV600E-mutated metastatic melanoma and non-small cell lung cancer. This study aimed to evaluate the efficacy and safety of daBRAFenib and trametinib in patients with metastatic BRAFV600E-mutated thyroid cancer. This was a retrospective study to evaluate the efficacy of daBRAFenib and trametinib in patients with metastatic BRAFV600E-mutated PTC. The patients received daBRAFenib 150 mg twice daily and trametinib 2 mg once daily at the Samsung Medical Center. This study evaluated the progression-free survival (PFS), objective response rate (ORR), disease control rate (DCR) overall survival (OS), and safety of daBRAFenib and trametinib. Between December 2019 and January 2022, 27 PTC patients including eight patients with poorly differentiated or anaplastic transformation, received daBRAFenib and trametinib. The median age was 73.0 years, and the median follow-up period was 19.8 months. The majority (81.5%) had undergone thyroidectomy, while 8 patients had received prior systemic treatments. ORR was 73.1%, with 19 partial responses, and DCR was 92.3%. Median PFS was 21.7 months, and median OS was 21.7 months. Treatment-related adverse events included generalized weakness (29.6%), fever (25.9%), and gastrointestinal problems (22.2%). Dose reduction due to adverse events was required in 81.5% of the patients. DaBRAFenib and trametinib demonstrated a high ORR with promising PFS; however, most patients with BRAFV600E-mutated metastatic PTC required a dose reduction.

Repeat Redifferentiation of Radioiodine Refractory BRAFV600E Mutated Thyroid Cancer With Dabrafenib.

N/A (Letter to the Editor).

Disulfiram/Cu Kills and Sensitizes BRAF-Mutant Thyroid Cancer Cells to BRAF Kinase Inhibitor by ROS-Dependently Relieving Feedback Activation of MAPK/ERK and PI3K/AKT Pathways

BRAFV600E, the most common genetic alteration, has become a major therapeutic target in thyroid cancer. Vemurafenib (PLX4032), a specific inhibitor of BRAFV600E kinase, exhibits antitumor activity in patients with BRAFV600E-mutated thyroid cancer. However, the clinical benefit of PLX4032 is often limited by short-term response and acquired resistance via heterogeneous feedback mechanisms. Disulfiram (DSF), an alcohol-aversion drug, shows potent antitumor efficacy in a copper (Cu)-dependent way. However, its antitumor activity in thyroid cancer and its effect on cellular response to BRAF kinase inhibitors remain unclear. Antitumor effects of DSF/Cu on BRAFV600E-mutated thyroid cancer cells and its effect on the response of these cells to BRAF kinase inhibitor PLX4032 were systematically assessed by a series of in vitro and in vivo functional experiments. The molecular mechanism underlying the sensitizing effect of DSF/Cu on PLX4032 was explored by Western blot and flow cytometry assays. DSF/Cu exhibited stronger inhibitory effects on the proliferation and colony formation of BRAFV600E-mutated thyroid cancer cells than DSF treatment alone. Further studies revealed that DSF/Cu killed thyroid cancer cells by ROS-dependent suppression of MAPK/ERK and PI3K/AKT signaling pathways. Our data also showed that DSF/Cu strikingly increased the response of BRAFV600E-mutated thyroid cancer cells to PLX4032. Mechanistically, DSF/Cu sensitizes BRAF-mutant thyroid cancer cells to PLX4032 by inhibiting HER3 and AKT in an ROS-dependent way and subsequently relieving feedback activation of MAPK/ERK and PI3K/AKT pathways. This study not only implies potential clinical use of DSF/Cu in cancer therapy but also provides a new therapeutic strategy for BRAFV600E-mutated thyroid cancers.

Supramolecular nanofibers co-loaded with dabrafenib and doxorubicin for targeted and synergistic therapy of differentiated thyroid carcinoma.

Rationale: Although surgery, radioiodine therapy, and thyroid hormone therapy are the primary clinical treatments for differentiated thyroid carcinoma (DTC), effective therapy for locally advanced or progressive DTC remains challenging. BRAF V600E, the most common BRAF mutation subtype, is highly related to DTC. Previous studies prove that combination of kinase inhibitors and chemotherapeutic drugs may be a potential approach for DTC treatment. In this study, a supramolecular peptide nanofiber (SPNs) co-loaded with dabrafenib (Da) and doxorubicin (Dox) was constructed for targeted and synergistic therapy with BRAF V600E+ DTC. Methods: A self-assembling peptide nanofiber (Biotin-GDFDFDYGRGD, termed SPNs) bearing biotin at the N-terminus and a cancer-targeting ligand RGD at the C-terminus was used as a carrier for co-loading Da and Dox. D-phenylalanine and D-tyrosine (DFDFDY) are used to improve the stability of peptides in vivo. Under multiple non-covalent interactions, SPNs/Da/Dox assembled into longer and denser nanofibers. RGD ligand endows self-assembled nanofibers with targeting cancer cells and co-delivery, thereby improving cellular uptake of payloads. Results: Both Da and Dox indicated decreased IC50 values upon encapsulation in SPNs. Co-delivery of Da and Dox by SPNs exhibited the strongest therapeutic effect in vitro and in vivo by inhibiting ERK phosphorylation in BRAF V600E mutant thyroid cancer cells. Moreover, SPNs enable efficient drug delivery and lower Dox dosage, thereby significantly reducing its side effects. Conclusion: This study proposes a promising paradigm for the synergistic treatment of DTC with Da and Dox using supramolecular self-assembled peptides as carriers.

1655P Dabrafenib and trametinib in patients with metastatic BRAFV600E-mutated thyroid cancer

Papillary thyroid cancer (PTC) is usually treated successfully with surgery and radioactive iodine therapy (RAI), but in some RAI-refractory patients with metastatic and symptomatic disease, systemic therapy could be considered. BRAF mutations are detected in over 80% of PTC in Korea. Dabrafenib plus trametinib showed promising efficacy in patients with metastatic melanoma or non-small cell lung cancer with BRAFV600E mutation. This study evaluated the efficacy and safety of dabrafenib plus trametinib in patients with metastatic BRAFV600E-mutated thyroid cancer. This is a retrospective study of dabrafenib plus trametinib in patients with metastatic BRAFV600E-mutated PTC or PTC with poorly differentiated or anaplastic transformation. Patients had symptomatic disease and progressed in 12 months prior to treatment. Patients received dabrafenib 150mg twice daily and trametinib 2mg once daily as part of the Expanded Access Program at Samsung Medical Center. This study evaluated objective response rate (ORR), safety, and tolerability of dabrafenib plus trametinib. Between December 2019 and January 2022, 25 patients with PTC received dabrafenib plus trametinib (poorly differentiated or anaplastic feature, n=8). Median age was 73.0 years (range, 24-84), the median follow-up was 6.8 months (range, 1.0-28.4). Twenty-two patients received thyroidectomy (3 with initial stage IV) and 8 patients received prior systemic treatment (4 patients with lenvatinib, 3 with sorafenib, 1 with pembrolizumab plus lenvatinib). The median cycle of dabrafenib plus trametinib was 5.9 (range, 1.1-30.4). The site of distant metastasis was lung (n=23), brain (n=3), and bone (n=3). The ORR was 72.0% (18 of PR) and disease control rate was 88.0%. The progression-free survival (PFS) rate at 6 months was 83.6%. Treatment-related adverse events were pyrexia (48.0%), generalized weakness (24.0%), and skin rash (12.0%). Dose reduction due to adverse event was required in 84.0% of patients. Dabrafenib plus trametinib showed high ORR with symptom improvement, however, majority of patients needed dose reduction in patients with BRAFV600E-mutated metastatic PTC. Additional follow-up period is needed for mature data of PFS and overall survival.

Abstract PR09: Phase 1 clinical safety and efficacy of ASN007, a novel oral ERK1/2 inhibitor, in patients with RAS, RAF or MEK mutant advanced solid tumors

Abstract Background: The oncogenic mitogen-activated protein kinase (MAPK) pathway is dysregulated in a broad range of cancers through mutations in BRAF, KRAS, NRAS, HRAS and MEK1 genes. ASN007 is a novel, potent and orally bioavailable inhibitor of ERK1/2 kinases (IC50 1-2nM) with a very long target residence time (550 min). Preclinical studies show strong anti-tumor activity in multiple RAS mutant xenograft and PDX models, irrespective of mutation subtype. ASN007 also maintains strong activity in BRAF mutant melanoma PDX models resistant to BRAF and MEK inhibition. Preclinical activity is seen with both intermittent as well as daily dosing. This is the initial report of ASN007 clinical data from this first-in-human Phase 1 Study. Methods: This Phase 1 trial evaluates ASN007 in patients (PS 0-1) with metastatic solid tumors refractory to standard therapies using an accelerated dose titration design for once daily (QD) and once weekly (QW) oral dosing (NCT03415126). Primary objectives in Part A (dose finding) include safety, tolerability, PK and PD to determine the Maximum Tolerated Dose (MTD). Part B (disease specific expansion) will evaluate clinical activity in cohorts of 15 patients each with tumors harboring specific mutations which include NRAS, HRAS, MEK1 and BRAF. Results: To date, 42 eligible patients (pts) were enrolled at dose levels ranging from 10mg to 80mg QD and 80 mg to 350mg QW. The respective MTDs are 40mg QD and 250mg QW. Reversible treatment-related adverse events (TRAEs) at 40mg QD (n=10) included rash ( 90%, Gr3 10%), nausea/vomiting (Gr1 30%), diarrhea (Gr1 30%), fatigue (20%, Gr3 10%) and central serous retinopathy (CSR) (30%, no G3) and at 250mg QW (n=9) included rash (33%, no Gr3), CSR (11%, Gr3 11%), blurred vision (44%, Gr3 11%), nausea/vomiting (33%, Gr3 11%) and diarrhea (33%, no Gr3). Dose limiting toxicities (DLTs) included Gr3 CSR at 60 and 80 QD, Gr3 rash at 80mg QD and Gr3 AST at 350mg QW. Durable clinical benefit was noted for 3 pts treated with QW ASN007 at doses 120 mg to 250 mg: a confirmed partial response (-57%) in a patient with HRAS-mutant salivary gland cancer for 5+ months, stable disease in KRAS mutant ovarian cancer for 9+ months and stable disease in BRAF V600E mutant thyroid cancer for 8+ months. Pharmacokinetic studies demonstrated dose dependent increase in the Cmax and AUC24 with both QD and QW dosing. QW dosing Cmax levels exceed average IC50 values more than >30-fold. Inter-subject variability was moderate (≤ 50%) and the elimination t1/2 was 10-15 hours. Conclusions: ASN007 is a selective oral inhibitor of ERK1/2 with a long target residence time. QD or QW dosing is feasible with expected reversible and manageable AE profile and dose dependent exposure. The dose of 250mg QW was selected for further development due to favorable tolerability and encouraging signs of clinical activity. Part B of the study is open to enroll patients with solid tumors harboring BRAF, MEK1, and RAS mutations. Updated clinical, safety, PK/PD and efficacy data will be presented. Citation Format: Anthony W. Tolcher, Ryan J. Sullivan, Drew W. Rasco, Zeynep Eroglu, Nehal Lakhani, Dana Kessler, Helen Usansky, Sanjeeva Reddy, Louis J. Denis, Filip Janku. Phase 1 clinical safety and efficacy of ASN007, a novel oral ERK1/2 inhibitor, in patients with RAS, RAF or MEK mutant advanced solid tumors [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference on Molecular Targets and Cancer Therapeutics; 2019 Oct 26-30; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2019;18(12 Suppl):Abstract nr PR09. doi:10.1158/1535-7163.TARG-19-PR09

Inhibiting BRAF Oncogene–Mediated Radioresistance Effectively Radiosensitizes BRAFV600E-Mutant Thyroid Cancer Cells by Constraining DNA Double-Strand Break Repair

Activating BRAF mutations, most commonly BRAFV600E, are a major oncogenic driver of many cancers. We explored whether BRAFV600E promotes radiation resistance and whether selectively targeting BRAFV600E with a BRAF inhibitor (vemurafenib, BRAFi) sensitizes BRAFV600E thyroid cancer cells to radiotherapy. Immunoblotting, neutral comet, immunocytochemistry, functional reporter, and clonogenic assays were used to analyze the outcome and molecular characteristics following radiotherapy with or without BRAFV600E or vemurafenib in thyroid cancer cells. BRAFV600E thyroid cancer cell lines were associated with resistance to ionizing radiation (IR), and expression of BRAFV600E into wild-type BRAF thyroid cancer cells led to IR resistance. BRAFi inhibited ERK signaling in BRAFV600E mutants, but not BRAF wild-type thyroid cancer cell lines. BRAFi selectively radiosensitized and delayed resolution of IR-induced γH2AX nuclear foci in BRAFV600E cells. Moreover, BRAFi impaired global DNA repair and altered the resolution of 53BP1 and RAD51 nuclear foci in BRAFV600E cells following IR. BRAFV600E mutants displayed enhanced nonhomologous end-joining (NHEJ) repair activity, which was abolished by BRAFi. Intriguingly, BRAFV600E mutation led to upregulation of XLF, a component of NHEJ, which was prevented by BRAFi. Importantly, BRAFi in combination with radiotherapy resulted in marked and sustained tumor regression of BRAFV600E thyroid tumor xenografts. BRAFV600E mutation promotes NHEJ activity leading to radioresistance and BRAFi selectively radiosensitizes BRAFV600E thyroid cancer cells through inhibiting NHEJ. Our findings suggest that combining BRAFi and radiation may improve the therapeutic outcome of patients with BRAFV600E-mutant thyroid cancer.

MAPK- and AKT-activated thyroid cancers are sensitive to group I PAK inhibition.

The number of individuals who succumb to thyroid cancer has been increasing and those who are refractory to standard care have limited therapeutic options, highlighting the importance of developing new treatments for patients with aggressive forms of the disease. Mutational activation of MAPK signaling, through BRAF and RAS mutations and/or gene rearrangements, and activation of PI3K signaling, through mutational activation of PIK3CA or loss of PTEN, are well described in aggressive thyroid cancer. We previously reported overactivation and overexpression of p21-activated kinases (PAKs) in aggressive human thyroid cancer invasive fronts and determined that PAK1 functionally regulated thyroid cancer cell migration. We reported mechanistic crosstalk between the MAPK and PAK pathways that are BRAF-dependent but MEK independent, suggesting that PAK and MEK inhibition might be synergistic. In the present study, we tested this hypothesis. Pharmacologic inhibition of group I PAKs using two PAK kinase inhibitors, G-5555 or FRAX1036, reduced thyroid cancer cell viability, cell cycle progression and migration and invasion, with greater potency for G-5555. Combination of G-5555 with vemurafenib was synergistic in BRAFV600E-mutated thyroid cancer cell lines. Finally, G-5555 restrained thyroid size of BRAFV600E-driven murine papillary thyroid cancer by >50% (P < 0.0001) and reduced carcinoma formation (P = 0.0167), despite maintenance of MAPK activity. Taken together, these findings suggest both that group I PAKs may be a new therapeutic target for thyroid cancer and that PAK activation is functionally important for BRAFV600E-mediated thyroid cancer development.

Mitochondrial metabolism is inhibited by the HIF1α-MYC-PGC-1β axis in BRAF V600E thyroid cancer.

BRAF V600E is the most common mutation identified in thyroid cancers. However, the relationship between BRAF V600E and metabolic reprogramming in thyroid cancer is unclear. Here, we investigate the mechanism of metabolic reprogramming in BRAF V600E thyroid cancer by constructing BRAF V600E-overexpressing and BRAF-knockdown thyroid cell lines for use in mitochondrial respiration and glycolysis experiments. Western blot and RT-qPCR were performed to measure the level of metabolism-related proteins, and various approaches were used to investigate transcriptional regulation. In thyroid cancer cells, the overexpression of BRAF V600E inhibited OXPHOS gene expression and mitochondrial respiration but enhanced aerobic glycolysis. Clinical thyroid cancer samples carrying the BRAF V600E mutation had suppressed levels of PGC-1β but increased expression of HIF1α. Our results show that BRAF V600E reduced mitochondrial respiration by decreasing the expression of PGC-1β. In addition, HIF1α, which is a target of BRAF V600E, was found to regulate the expression of PGC-1β via MYC. Furthermore, glycolysis-related enzymes, such as LDHA and PKM2, were upregulated in BRAF V600E mutant thyroid cancer specimens, thereby promoting glycolysis. MEK1/2 inhibitor treatment enhanced the specific dependence of BRAF V600E mutant thyroid cancer on mitochondrial respiration. These results indicate that in thyroid cancer, the BRAF V600E mutation alters the HIF1α-MYC-PGC-1β axis, causing mitochondrial respiration to be inhibited and aerobic glycolysis to be enhanced.

BRAF Oncogenic Activation Induces Radioresistance Through Non-homologous End-Joining Repair Which is Abrogated by Targeted Inhibition of BRAF Mutational Activity

BRAF activating mutations, most commonly BRAFV600E/K, are driver mutations commonly found in solid tumors for which ionizing radiation (IR) is used, including thyroid, melanoma, colorectal, and lung cancer. Whether BRAFV600E mutation fosters radioresistance through nuclear DNA repair mechanisms is unclear. We hypothesize that BRAFV600E promotes radioresistance through heightened double-strand break repair mechanisms, which can be attenuated by targeted inhibition of the BRAF oncogene. We tested the effects of a BRAFV600E mutation using papillary and anaplastic thyroid cancer cell lines that possessed either wild-type or mutant BRAFV600E. We evaluated the role of BRAF and downstream targets in radiation clonogenic, neutral comet, nuclear foci, immunofluorescence, immunoblotting, RT-PCR, functional DNA repair reporter, and in vivo tumor growth assays. Radiation clonogenic assay showed BRAFV600E thyroid cancer cell lines were resistant to IR, and introduction of BRAFV600E into wild-type BRAF thyroid cancer TPC-1 cells led to significant IR resistance (dose enhancement factor, DEF 0.70). Selectively targeting BRAFV600E with a potent mutant BRAF inhibitor (vemurafenib, Vem) significantly sensitized BRAFV600E to IR, but not wild-type BRAF thyroid cancer cells (DEFs 1.37-1.78). Immunoblotting demonstrates that vemurafenib potently inhibited ERK signaling in BRAFV600E mutants but not BRAF wild-type cells. Vem delayed DNA repair in BRAFV600E cells after IR as evidenced by comet tail assays at 15 min, 1, 6, and 24 hrs (p<0.005) and γ-H2AX nuclear foci assays at 6 and 24 hrs (p<0.01). Moreover, Vem altered the kinetics of 53BP and RAD51 nuclear foci in BRAFV600E cells at 6 and 24 hrs after IR (p<0.05). Assessment of double-strand DNA repair using functional reporter assays revealed that BRAFV600E mutant was associated with enhanced non-homologous end-joining (NHEJ) repair activity, while Vem significantly reduced NHEJ repair activity by ∼40% (p<0.01). BRAFV600E mutation led to upregulation of XLF, a nuclear protein involved in NHEJ-mediated DNA repair, in thyroid cancer cell lines and in the publicly-available TCGA dataset (p<2.4e-14). Additionally, Vem treatment resulted in decreased XLF expression and genetic down-regulation of XLF sensitized BRAFV600E cells to IR (p<0.05). Importantly, Vem in combination with IR resulted in sustained tumor regression of BRAFV600E thyroid tumor xenografts, with minimal evidence of tumor regrowth after 60 days. BRAFV600E mutation promotes NHEJ activity leading to radioresistance, and Vem selectively radiosensitizes BRAFV600E thyroid cancer cells by inhibiting NHEJ repair. Our findings suggest that combining BRAF inhibition and IR may improve the therapeutic outcome for patients with BRAFV600E mutant thyroid cancer.

The Relationship of BrafV600E Mutation Status to FDG PET/CT Avidity in Thyroid Cancer: A Review and Meta-Analysis

Papillary thyroid cancer (PTC) harboring a BRAFV600E gene mutation has been shown to exhibit aggressive tumor behavior and carries higher risks of recurrence and disease-specific death. In this systematic review and meta-analysis, we examined published evidence related to the accuracy of fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in detection of residual disease in patients with BRAFV600E mutated thyroid cancer. We extracted data from PUBMED/MEDLINE and EMBASE published between January 1995 and March 2017. We included studies that compared FDG PET standardized uptake values (SUVs) between BRAFV600E-positive and BRAFV600E-negative subjects, as well as those that evaluated the odds of having FDG avidity between BRAFV600E-positive and -negative patients with thyroid cancer. There were a total of 12 studies in the systematic review. Seven studies qualified for the analysis for calculating the pooled odds ratio (OR). The pooled cohort with binary data had 1,144 patients out of which 843 were BRAFV600E positive and 301 were BRAFV600E negative. Those with a BRAFV600E mutation had a significantly greater likelihood of having FDG-avid lesions. The pooled OR was 2.12 (confidence interval [CI] 1.53-3.00, P<.01). The pooled mean SUV (cohort of 315 patients) was significantly higher in BRAFV600E-positive compared to BRAFV600E negative patients, with a pooled mean difference of 5.1 (CI 4.3-5.8). Our meta-analysis shows that presence of BRAFV600E mutation in PTC confers a higher likelihood of FDG PET avidity and is associated with higher SUV uptake values compared to BRAFV600E-mutation negative status. BRAF = B-Raf proto-oncogene, serine/threonine kinase; CI = confidence interval; CT = computed tomography; DTC = differentiated thyroid cancer; FDG = fluorodeoxyglucose; PET = positron emission tomography; PTC = papillary thyroid cancer; SUV = standardized uptake value.

Abstract 1709: The effect of a XIAP inhibitor, embelin, on apoptosis of thyroid cancer cell lines

Abstract X-linked inhibitor of apoptosis protein (XIAP) is a member of the inhibitor of apoptosis (IAP) protein family that selectively blocks caspases-3, -7, -9 and inhibits cell death. Embelin, a XIAP inhibitor, is known to exhibit anti-inflammatory and apoptotic activities. Recent reports suggest that embelin interferes the signal transducer and activator of transcription 3 (STAT3) pathway and nuclear factor-kB (NF-kB) signal pathway. In this study, we investigated the anti-cancer efficacy of embelin by measuring its effects on apoptosis of thyroid cancer cell lines. We also explored the mechanism underlying these effects. We found that embelin induced the apoptosis of human thyroid cancer cell lines, such as FTC-133, CAL-62, KTC-1, and 8505C. The effect was stronger in BRAF V600E-mutant thyroid cancer cell lines (KTC-1 and 8505C) than wild-type cell lines (FTC-133 and CAL-62). The effect of embelin on cell apoptosis was associated with increased phosphorylation of p38. SB203580 inhibited the embelin mediated induction of cleaved caspase-3 activity in V600E mutant thyroid cancer cell lines. Interestingly, embelin induced apoptosis in BRAF wild type cancer cell lines, even after treatment of SB203580. These results indicated that another signaling pathway, not a p38 pathway, might be existed for embelin induced apoptosis in BRAF wild type thyroid cancer cell. In conclusion, embelin-induced XIAP suppression resulted in an increase of apoptosis via phosphorylation of p38 in BRAF V600E-mutant thyroid cancer cell lines. Regulation of XIAP activity may be potentially useful as a treatment of thyroid cancer, especially in BRAF V600E-mutant thyroid cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1709. doi:1538-7445.AM2012-1709

The influence of the BRAF V600E mutation in thyroid cancer cell lines on the anticancer effects of 5-aminoimidazole-4-carboxamide-ribonucleoside

5-Aminoimidazole-4-carboxamide-ribonucleoside (AICAR) is an activator of 5'-AMP-activated protein kinase (AMPK), which plays a role in the maintenance of cellular energy homeostasis. Activated AMPK inhibits the protein kinase mechanistic target of rapamycin, thereby reducing the extent of protein translation and suppressing both cell growth and cell cycle entry. Recent reports indicate that AMPK-mediated growth inhibition is achieved via an action of the RAF-MEK-ERK mitogen-activated protein kinase pathway in melanoma cells harboring the V600E mutant form of the BRAF oncogene. In this study, we investigated the anti-cancer efficacy of AICAR by measuring its effects on proliferation, apoptosis, and cell cycle progression of BRAF wild-type and V600E-mutant thyroid cancer cell lines. We also explored the mechanism underlying these effects. AICAR inhibited the proliferation of BRAF V600E-mutant thyroid cancer cell lines more strongly than was the case with wild-type cell lines. The suppressive effect of AICAR on cell proliferation was associated with increased S-phase cell cycle arrest and apoptosis. Interestingly, AICAR suppressed phosphorylation of ERK and p70S6K in BRAF V600E-mutant thyroid cancer cells, but rather increased phosphorylation in wild-type cells. Together, the results indicate that AICAR-induced AMPK activation in BRAF V600E-mutant thyroid cancer cell lines resulted in increases in apoptosis and S-phase arrest via downregulation of ERK and p70S6K activity. Thus, regulation of AMPK activity may be potentially useful as a therapy for thyroid cancer if the cancer harbors a BRAF V600E mutation.

Abstract 4471: Antitumor effects of 5-Aminoimidazole-4-carboxamide-ribonucleoside (AICAR) on thyroid cancer cell lines with BRAF V600E mutation

Abstract Background : Anaplastic thyroid carcinoma is one of the most aggressive human cancers with a median survival of only 6 months. Local surgical tumor debulking and combined with radio-chemotherapy is conventionally used but low success rate urges the search for new therapeutic targets. 5-Aminoimidazole-4-carboxamide-ribonucleoside (AICAR) is an activator of the 5’ AMP-activated protein kinase (AMPK), which plays a role in cellular energy homeostasis. Activated AMPK is inhibits the protein kinase mammalian target of rapamycin, thereby reducing protein translation and suppressing cell growth and cell cycle entry. Recently, AMPK was reported to be mediated by RAF-MEK-ERK pathway in melanoma cells harboring the B-RAF(V600E) mutation. Methods: We investigated the anti-tumor effect of AICAR on the proliferation of thyroid cancer cell lines with BRAF(V600E) mutation or wild type BRAF. We were to see the effect of AICAR on cell proliferation, apoptosis and cell cycle of thyroid cancer cell and reveal the mechanism of these changes. Methods: The proliferation of thyroid cancer cell lines with BRAF(V600E) mutations was more significantly inhibited by administration of AICAR in comparison with cell lines with wild type BRAF. The suppressive effect of AICAR on cell proliferation of BRAF(V600E) mutated thyroid cancer cell lines was related with increased phosphorylation of AMPK, S-phase cell cycle arrest, and increased apoptosis. Interestingly, the AICAR suppressed phosphorylation of ERK and p70S6K in B-RAF V600E mutated thyroid cancer cells compared to B-RAF wild type cells. Conclusion: In BRAF(V600E) mutation harboring thyroid cancer cell lines, AICAR induced AMPK activation resulted in decrease of cell growth, apoptosis, and increased cell cycle arrest via down-regulation of ERK and p70S6K activity. These results suggest that regulation of AMPK activity may be a potential target for cancer therapy in thyroid cancer with BRAF V600E mutation. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4471. doi:10.1158/1538-7445.AM2011-4471