BRAF-mutated Melanoma Patients Research Articles

Long Term Results and Prognostic Biomarkers for Anti-PD1 Immunotherapy Used after BRAFi/MEKi Combination in Advanced Cutaneous Melanoma Patients.

Simple SummarySecond line anti-PD1 immunotherapy is effective in selected BRAF-mutated melanoma patients after BRAFi/MEKi immunotherapy failure. Nivolumab and pembrolizumab are of similar efficacy as a second line therapy. Worse performance status as well as high LDH levels are negative clinical biomarkers that correlated with shorter OS. The presence of brain and liver metastases correlates with shorter PFS and OS of these patients.(1) Background: BRAFi/MEKi are usually offered as a first line treatment for patients requiring rapid response; with elevated lactate dehydrogenase (LDH) activity, large tumor burden, and with brain metastases. The efficacy of second line therapies after BRAFi/MEKI failure is now well defined. (2) Methods: Patients treated with first line target BRAFi/MEKi therapy (vemurafenib plus cobimetinib, dabrafenib plus trametinib or encorafenib plus binimetinib); and for the second line treatment immunotherapy with programmed cell death 1 (PD-1) checkpoint inhibitors (nivolumab or pembrolizumab) with at least one cycle of second line were analyzed for survival and prognostic biomarkers. (3) Results: There were no statistically significant differences in ORR between the treatment groups with nivolumab and pembrolizumab, as well as median progression free-survival (PSF) and overall survival (OS) since the initiation of second line therapy; on nivolumab OS was 6.6 months, and on pembrolizumab 5.0 months. The greatest clinical benefit with second line immunotherapy was observed in patients with LDH ≤ ULN and <3 organ sites with metastasis at baseline. Longer OS was also noted in patients with time to PD >6 months in first line (slow progression). (4) Conclusions: Second line anti-PD1 immunotherapy is effective in BRAF-mutated melanoma patients after BRAFi/MEKi therapy failure.

The Role of Treatment Sequencing with Immune-Checkpoint Inhibitors and BRAF/MEK Inhibitors for Response and Survival of Patients with BRAFV600-Mutant Metastatic Melanoma-A Retrospective, Real-World Cohort Study.

Simple SummaryThe clinical application of kinase inhibitors and immune-checkpoint inhibitors (CPI) has substantially improved the treatment landscape of melanoma. While BRAF/MEK inhibitors allow for rapid disease control, and CPI can evoke durable tumor responses, primary and secondary resistance frequently limit treatment efficacy. Observations from preclinical trials suggest that treatment with BRAF/MEK inhibitors may enhance susceptibility towards CPI therapy and thus improve long-term tumor control. To date, little prospective data is available for the optimal sequencing of these agents in melanoma patients. In this retrospective, real-world analysis, we analyzed the role of sequential treatment with BRAF/MEK inhibitors and CPI in 135 BRAF-mutant, metastatic melanoma patients. Our results demonstrate that front-line treatment with CPI is associated with favorable tumor control and overall survival in patients with BRAF-mutant melanoma. Further, our data indicate that patients who are refractory to front-line BRAF/MEKi therapy are at higher risk of rapid disease progression compared to patients with front-line CPI treatment.The advent of immune-checkpoint inhibitors (CPI) and BRAF/MEK-directed targeted therapy (TT) has improved the treatment landscape of patients with BRAFV600-mutant metastatic melanoma. While TT allows for rapid disease control, the development of secondary TT resistance limits the duration of responses. Responses to CPI have a slower onset but can be durable in a subset of patients. To date, little prospective data is available for the optimal sequencing of these agents in melanoma patients. In this retrospective, single-center, real-world analysis, we identified 135 patients with BRAF-mutated, metastatic melanoma who received consecutive treatment with TT followed by CPI, or vice versa, as first and second-line therapy, respectively. We collected data on clinical-pathological factors, treatment duration, best overall response, progression-free survival and overall survival (OS). Our data revealed that front-line treatment with CPI, followed by TT, showed a non-significant trend towards better OS compared to front-line TT (median OS: 35.0 vs. 18.0 months, p = 0.070). This association was confirmed in a subgroup of patients without systemic pre-treatments (median OS: 41.0 vs. 14.0 months, p = 0.02). Further, we observed significantly better objective response rates to second-line treatments for patients receiving front-line CPI (18.4 vs. 37.8%, p = 0.024). Last, our results indicated that rapid disease progression was less common in patients treated with front-line CPI (27.6% vs. 16.2%) and that subsequent treatment with TT resulted in favorable survival outcomes. Our real-world data indicate that sequential treatment with front-line CPI is associated with favorable tumor control and overall survival in a subgroup of previously untreated BRAF-mutant metastatic melanoma patients.

Real-world treatment patterns and overall survivalin BRAF-mutant melanoma patients treated with immunotherapy or targeted therapy.

Aim: To assess overall survival (OS) in patients with advanced BRAF-mutant melanoma by first-line (1L) targeted therapy (TT) or checkpoint inhibitor (CPI) use, second-line (2L) TT or CPI use, and treatment sequence. Patients & methods: Advanced BRAF-mutant melanoma patients treated with 1L CPI or TT were selected from a real-world, electronic health record-derived database. Results: CPI was associated with improved survival after adjustment for potential confounders (hazard ratio, 0.75 [95% CI, 0.66-0.87]). Median OS was similar between 2L therapies and among likely treatment sequences. Conclusion: This real-world study demonstrated a survival benefit with 1L CPI versus TT. Analyses of 2L and treatment sequences were unable to detect or rule out clinically relevant differences in OS.

Long-Term Outcomes of Targeted Therapy after First-Line Immunotherapy in BRAF-Mutated Advanced Cutaneous Melanoma Patients-Real-World Evidence.

Background: Currently, limited data on targeted therapy and immunotherapy sequencing in patients with BRAF-mutant melanoma is available. Targeted therapy and immunotherapy are expected to be comparable in terms of overall survival (OS) when used as second-line therapies; therefore, understanding the characteristics of patients who completed sequential treatment is needed. Methods: The primary objective of this study was to analyze the efficacy of BRAFi/MEKi activity as second-line therapy in patients with advanced melanoma. We also aimed to describe the clinical characteristics of patients with advanced melanoma who were treated sequentially with immunotherapy and targeted therapy. We enrolled 97 patients treated between 1st December 2015 and 31st December 2020 with first-line immunotherapy with programmed cell death 1 (PD-1) checkpoint inhibitors; and for the second-line treatment with at least one cycle of BRAFi/MEKi therapy with follow-up through 31 January 2022. Results: Median OS since first-line treatment initiation was 19.9 months and 12.8 months since initiation of BRAFi/MEKi treatment. All BRAFi/MRKi combinations were similarly effective. Median progression free survival (PFS) was 7.5 months since initiation of any BRAFi/MEKi treatment. Conclusions: BRAFi/MEKi therapy is effective in the second-line in advanced and metastatic melanoma patients. For the first time, the efficacy of all BRAFi/MEKi combinations as second-line therapy is shown.

Real-World Evidence of Systemic Therapy Sequencing on Overall Survival for Patients with Metastatic BRAF-Mutated Cutaneous Melanoma.

Aim: To evaluate optimal systemic therapy sequencing (first-line targeted therapy (1L-TT) vs. first-line immunotherapy (1L-IO)) in patients with BRAF-mutated metastatic melanoma. Methods: Nation-wide prospective data of patients with newly diagnosed BRAF-mutated metastatic melanoma were retrieved from the Canadian Melanoma Research Network. Results: Our study included 79 and 107 patients in the 1L-IO and 1L-TT groups, respectively. There were more patients with ECOG 0–1 (91% vs. 72%, p = 0.023) in the 1L-IO group compared to the 1L-TT group. Multivariable Cox analysis suggested no OS differences between the two groups (HR 0.838, 95%CI 0.502–1.400, p = 0.500). However, patients who received 1L-TT then 2L-IO had the longest OS compared to 1L-IO without 2L therapy, 1L-IO then 2L-TT, and 1L-TT without 2L therapy (38.3 vs. 32.2 vs. 16.9 vs. 6.3 months, p < 0.001). For patients who received 2L therapy, those who received 2L-IO had a trend towards OS improvement compared with the 2L-TT group (21.7 vs. 8.9 months, p = 0.053). Conclusions: Our nation-wide prospective study failed to establish any optimal systemic therapy sequencing in advanced BRAF-mutant melanoma patients. Nevertheless, we provided evidence that immunotherapy has durable efficacy in advanced BRAF-mutant melanoma patients, regardless of treatment line, and that Canadian medical oncologists were selecting the appropriate treatment sequences in a real-world setting, based on patients’ clinical and tumour characteristics.

Identification of a miRNA-based non-invasive predictive biomarker of response to target therapy in BRAF-mutant melanoma.

Rationale: Metastatic melanoma is the most aggressive and dangerous form of skin cancer. The introduction of immunotherapy with Immune checkpoint Inhibitors (ICI) and of targeted therapy with BRAF and MEK inhibitors for BRAF mutated melanoma, has greatly improved the clinical outcome of these patients. Nevertheless, response to therapy remains highly variable and the development of drug resistance continues to be a daunting challenge. Within this context there is a need to develop diagnostic tools capable of predicting response or resistance to therapy in order to select the best therapeutic approach. Over the years, accumulating evidence brought to light the role of microRNAs (miRNAs) as disease biomarkers. Methods: In particular, the detection of miRNAs in whole blood or specific blood components such as serum or plasma, allows these molecules to be good candidates for diagnosis, prognosis and for monitoring response to anticancer therapy. In this paper, we evaluated circulating basal levels of 6 previously identified miRNAs in serum samples of 70 BRAF-mutant melanoma patients before starting targeted therapy. Results: Results show that the circulating levels of the oncosuppressor miR-579-3p and of the oncomiR miR-4488 are able to predict progression free survival (PFS) but not overall survival (OS). Most importantly, we observed that the best predictor of disease outcome is represented by the ratio of circulating miR-4488 vs. miR-579-3p (miRatio). Finally, the combination of the Lactate dehydrogenase (LDH) blood levels with the two circulating miRNAs alone or together did not produce any improvement in predicting PFS indicating that miR-579-3p and miR-4488 are independent predictors of PFS as compared to LDH. Conclusions: All together these data underscored the relevance of circulating miRNAs as suitable tools to predict therapy response in melanoma and maybe further developed as companion diagnostics in the clinic.

Intermittent BRAF inhibition in advanced BRAF mutated melanoma results of a phase II randomized trial

Combination treatment with BRAF (BRAFi) plus MEK inhibitors (MEKi) has demonstrated survival benefit in patients with advanced melanoma harboring activating BRAF mutations. Previous preclinical studies suggested that an intermittent dosing of these drugs could delay the emergence of resistance. Contrary to expectations, the first published phase 2 randomized study comparing continuous versus intermittent schedule of dabrafenib (BRAFi) plus trametinib (MEKi) demonstrated a detrimental effect of the “on−off” schedule. Here we report confirmatory data from the Phase II randomized open-label clinical trial comparing the antitumoral activity of the standard schedule versus an intermittent combination of vemurafenib (BRAFi) plus cobimetinib (MEKi) in advanced BRAF mutant melanoma patients (NCT02583516). The trial did not meet its primary endpoint of progression free survival (PFS) improvement. Our results show that the antitumor activity of the experimental intermittent schedule of vemurafenib plus cobimetinib is not superior to the standard continuous schedule. Detection of BRAF mutation in cell free tumor DNA has prognostic value for survival and its dynamics has an excellent correlation with clinical response, but not with progression. NGS analysis demonstrated de novo mutations in resistant cases.

IGF1R/IR Mediates Resistance to BRAF and MEK Inhibitors in BRAF-Mutant Melanoma.

Simple SummaryMelanoma accounts for only 4% of skin cancer, but is the major cause of skin cancer related deaths. The use of dabrafenib (BRAF inhibitor) and trametinib (MEK inhibitor), two FDA approved drugs to treat patients with BRAFV600E melanoma, is limited in the clinic due to the development of resistance. The IGF family of receptors is known to play a crucial role in cancer progression. In our in vitro screening, we identified that the activation of Insulin-like growth factor 1 receptor (IGF1R) and Insulin Receptor (IR) mediates resistance to dabrafenib and trametinib. Patients with high levels of IGF1R and IR have worse survival outcomes compared to patients with low levels of these receptors. We demonstrate that combining dabrafenib and trametinib with an IGF1R/IR inhibitor, BMS-754807, in vitro and in vivo, is efficacious and inhibits proliferation and tumor growth. This research opens up avenues for the development of novel and potent IGF1R/IR inhibitors for patients with BRAF-mutant melanoma.The use of BRAF and MEK inhibitors for patients with BRAF-mutant melanoma is limited as patients relapse on treatment as quickly as 6 months due to acquired resistance. We generated trametinib and dabrafenib resistant melanoma (TDR) cell lines to the MEK and BRAF inhibitors, respectively. TDR cells exhibited increased viability and maintenance of downstream p-ERK and p-Akt as compared to parental cells. Receptor tyrosine kinase arrays revealed an increase in p-IGF1R and p-IR in the drug resistant cells versus drug sensitive cells. RNA-sequencing analysis identified IGF1R and INSR upregulated in resistant cell lines compared to parental cells. Analysis of TCGA PanCancer Atlas (skin cutaneous melanoma) showed that patients with a BRAF mutation and high levels of IGF1R and INSR had a worse overall survival. BMS-754807, an IGF1R/IR inhibitor, suppressed cell proliferation along with inhibition of intracellular p-Akt in TDR cells. Dual inhibition of IGF1R and INSR using siRNA reduced cell proliferation. The combination of dabrafenib, trametinib, and BMS-754807 treatment reduced in vivo xenograft tumor growth. Examining the role of IGF1R and IR in mediating resistance to BRAF and MEK inhibitors will expand possible treatment options to aid in long-term success for BRAF-mutant melanoma patients.

Should Targeted Therapy Be Continued in BRAF-Mutant Melanoma Patients after Complete Remission?

Background: Targeted therapy is used to treat patients with a BRAF-mutated metastatic melanoma and is continued until disease progression or severe toxicity. No robust data on the management of patients achieving a complete remission (CR) are available. Main Objective: To determine the relapse rate in the first year after targeted therapy discontinuation in patients in CR. Secondary Objectives: To determine the relapse rates throughout the follow-up and to identify prognostic factors for relapse at 1 year. Methods: A retrospective, monocentric observational study was conducted in patients with advanced melanoma included in the RIC-Mel database who discontinued targeted therapy after achieving a CR confirmed by CT scan and PET/CT scan. Results: Twenty-nine patients were included. Seventeen (58.6%) patients were treated with BRAF inhibitor (BRAFi) alone and 12 (41.4%) with a BRAFi combined with a MEK inhibitor (BRAFi + MEKi). The median treatment duration was 9.7 months. The relapse rates after discontinuation were 69% at 12 months (BRAFi: 70.6%; BRAFi + MEKi: 66.7%) and 76% at 36 months (BRAFi: 76.5%; BRAFi + MEKi: 75%). A non-significant trend towards a higher risk of relapse was found in women (p = 0.1; RR 3.36; 95% CI 0.77–17.07), in patients with an LDH level greater than the upper limits of normal (p = 0.58; RR 2.43; 95% CI 0.10–56.71), and when more than two metastatic sites were involved (p = 0.19; RR 4.6; 95% CI 0.46–46.51). After relapse, targeted therapy was resumed in 17 patients (7 with BRAFi; 10 with BRAFi + MEKi) with a response rate of 53%. Conclusions: This real-life study provided long-term data in patients who discontinued targeted therapy after CR. Most patients experienced a relapse in the first year after targeted therapy discontinuation, of whom 50% were in the first 3 months. After targeted therapy resumption, 53% of relapsing patients achieved an objective response. Patients should be followed during the first year after treatment discontinuation. In addition, patients with less than 3 metastatic sites, a baseline LDH level with normal ranges, men, and patients responding rapidly to treatment would be more likely to maintain a CR after treatment discontinuation.

Retrospective analysis of adjuvant therapy using dabrafenib plus trametinib in Japanese patients with advanced melanoma: analysis of 36 cases.

Patients with resected stage IIIB, IIIC and IIID melanomas have a high risk of recurrence. Therefore, an appropriate protocol for stage III melanoma is needed. Since adjuvant dabrafenib plus trametinib (D+T) combined therapy and anti-PD1 antibody (Ab) therapy reduce the risk of recurrence in patients with resected stage III BRAF-mutated melanoma, selecting the adjuvant therapy for BRAF-mutated melanoma is controversial. The efficacy and safety profiles of D+T combined therapy in the adjuvant setting were retrospectively analyzed in 36 Japanese. BRAF-mutated advanced melanoma patients. The relapse-free rate (RFR) at 12 months was 82.1% (95% confidential interval (CI), 63.9-92.6%). In the 21 patients who completed the protocol, the RFR at 12 months was 85.7% (95% CI, 64.5-95.9%). In the seven patients whose protocol was interrupted by adverse events, the RFR was 71.4% (95% CI, 35.2-92.4%). The incidence rate of any AEs for all patients was 69.7% (95% CI, 52.5-82.8%), including 13 cases of pyrexia, five cases of skin rash and four cases of liver dysfunction. The present study suggested that D+T therapy in the adjuvant setting is a useful and very tolerable protocol for BRAF-mutated melanoma in the Japanese population.

Abstract 422: Sequential targeted therapy and immunotherapy of a BRAF positive metastatic melanoma patient with BRAF inhibitor vemurafenib, MEK inhibitor cobimetnib and a novel PD-1 antibody Sintilimab

Abstract Targeted therapy has dramatically improved the outcome of BRAF mutated melanoma patients. However, its response is usually brisk and lacks the durability of immunotherapy. Decisions about targeted therapy alone, immunotherapy alone, targeted therapy/immunotherapy combination or immunotherapy after targeted therapy require an oncologist to comprehensively evaluate multiple clinical factors. Here we report the sequential treatment of a BRAF positive metastatic melanoma patient with non-standard regimes due to practical reasons. A 75-year old male patient presented a black cauliflower-like mass on back and bilateral axillary lymph nodes enlargement. Postoperative pathologic examination confirmed a nodular malignant melanoma of 1.6 cm in diameter and 0.7 cm thick. NGS sequencing of the tumor revealed the canonical BRAF V600E mutation. As vemurafenib was the only approved melanoma targeted therapy drug in China at the time of diagnosis, it was administered (960 mg bid) as first-line therapy since September 2019 and the patient's response was confirmed by the significant reduction and softening of the left axillary node. One month later the node rapidly enlarged to 15 cm, and the blood scab fell off followed by pulsatile massive hemorrhage (~1000 mL). We performed an emergent angiograph and a transarterial embolization (TAE), aimed at selectively occluding the tumor artery by using gelatin sponge particle and coils. The hemorrhage was significantly reduced after TAE therapy and a left axillary residual cavity was formed. When the patient presented a progression of lymph node metastases, BRAF/MEK inhibitor combination was selected as the second-line therapy from December 2019. He received vemurafenib at a dose of 480 mg bid combined with cobimetinib 60mg qd (3 consecutive weeks every 28 days), the treatment was ongoing till disease progression in April 2020. Immunohistochemical analysis of the biopsy specimen demonstrated PD-L1 expression in 4% of tumor cells and immunotherapy was chosen as the third-line therapy. Sintilimab, a PD-1 antibody approved in China for the treatment of classical Hodgkin lymphoma, is undergoing clincial trials for multiple solid tumors including melanoma. Given the high cost of immunotherapy and the fact that Sintilimab is the only PD-1 inhibitor included in China's National Reimbursement Drug List, the patient started off-label use of Sintilimab and achieved partial response. In summary, our patient had an unconventional timeline of multiple therapies including surgery, TAE, targeted therapy and immunotherapy. His case demonstrated that meaningful clinical responses can be achieved with sequential targeted therapy/immunotherapy in BRAF-mutated metastatic melanoma and the novel PD-1 antibody Sintilimab is worth further investigation for its efficacy in metastatic melanoma. Citation Format: Yu Zhang, Xiaomo Li, Tonghui Ma, Baoshan Cao. Sequential targeted therapy and immunotherapy of a BRAF positive metastatic melanoma patient with BRAF inhibitor vemurafenib, MEK inhibitor cobimetnib and a novel PD-1 antibody Sintilimab [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 422.

15604 Resistance to BRAF and MEK inhibitors in BRAF-mutant melanoma

The 5-year survival rate for patients diagnosed with metastatic melanoma is only 23%. Nearly half of patients diagnosed with melanoma have BRAF-mutant melanoma in which there is a driver mutation in the MAPK pathway, leading to over activation. Single-agent BRAF inhibitors had some success, but their long term efficacy is limited due to the development of resistance. Current standard of care includes a BRAF-inhibitor in combination with a MEK inhibitor in order to co-target the downstream MEK protein in the hopes of preventing reactivation of the pathway. It has been shown that this combination therapy has also met some difficulty due to the development of resistance. We generated BRAF inhibitor (dabrafenib) and MEK inhibitor (trametinib) resistant cell lines (TDR) by adding increasing concentration of the drugs to the parental cells (drug sensitive cells) for WM115 and WM983 (BRAF mutant melanoma cell lines) until they were rendered resistant. The TDR cells remained viable over increasing concentration of the inhibitor as assessed by the MTT assay. There was maintenance of p-ERK in the TDR cells, which was not observed for the parental cells under similar conditions. qPCR analysis demonstrated that TDR cells had elevated levels of the signaling molecules such as AXL, EGFR, HER3, and IGF1R. These molecules might be potential mediators of resistance to targeted therapy for BRAF-mutant melanoma. Examining potential mechanisms of resistance to BRAF and MEK inhibitors helps expand possible treatment options to aid in long-term success for BRAF-mutant melanoma patients.

Safety and efficacy evaluation of encorafenib plus binimetinib for the treatment of advanced BRAF-mutant melanoma patients

ABSTRACT Introduction Approximately 40–50% of patients with cutaneous melanoma harbor point mutations in BRAF. BRAF and MEK inhibitors in combination are now a standard therapy for advanced BRAF V600-mutated melanoma. Nevertheless, survival rates with the combination are limited, highlighting the need for further therapeutic improvement and strategies to overcome primary and acquired resistance. Areas covered Encorafenib, a highly selective BRAF inhibitor, was developed in combination with binimetinib, a potent, selective allosteric MEK1/2 inhibitor, to improve efficacy and tolerability over other approved combo-targeted therapies. This novel combination shows peculiar pharmacodynamic properties which translate in a higher on-target potency and paradox index. Consistent survival improvements for encorafenib and binimetinib in BRAF V600-mutated melanoma have been confirmed in clinical trials, with over 4 years of median follow up. Expert opinion the favorable survival results and the attractive toxicity profile suggest that encorafenib and binimetinib combination is an intriguing standard option when targeted therapies are considered as first line treatment in BRAF mutated melanoma patients. In the near future, results from ongoing clinical trials will provide information on the use of this novel combination in specific situation, including as adjuvant treatment or as a combination strategy.

Promising Strategies for Overcoming BRAF Inhibitor Resistance Based on Known Resistance Mechanisms.

Almost 50% of metastatic melanomas harbor BRAF mutations. Since 2011, BRAF inhibitors have exhibited striking clinical benefits in BRAF-mutant melanoma patients. Unfortunately, their therapeutic effects are often temporary. The resistance mechanisms vary and can be broadly classified as MAPK reactivation-dependent and -independent. Elucidation of these resistance mechanisms provides new insights into strategies for overcoming resistance. Indeed, several alternative treatment strategies, including changes in the mode of administration, combinations of BRAF and MEK inhibitors, and immunotherapy have been verified as beneficial to BRAF inhibitor-resistant melanoma patients. In this review, we discuss promising strategies for overcoming drug resistance and highlighting the prospects for discovering strategies to counteract BRAF inhibitor resistance.

Abstract 1894: Role of IGF1R in mediating resistance to MAPK pathway inhibitors in BRAF-mutant melanoma

Abstract Melanoma is the most aggressive form of skin cancer originating in the pigment producing melanocytes of the skin. The five year survival rate for patients diagnosed with metastatic melanoma is only 23%. Around 60% of the melanomas encompass the active BRAFV600E oncoprotein, which is critical for survival and proliferation of the melanoma cells as a consequence of hyperactivation of theMAPK pathway. This opened up avenues for development of BRAF inhibitors and subsequently the development of MEK inhibitors. Co-targeting of BRAF and MEK with Dabrafenib and Trametinib respectively, results in a response rate of about 70% in patients harboring the BRAF mutation. The use of these inhibitors is limited as patients relapse on treatment typically within 6 months due to the development of acquired resistance. Recent studies have identified various resistance mechanisms including involvement of various receptor tyrosine kinases. In order to decipher novel mechanisms of resistance, we generated double resistant cell lines to BRAF and MEK inhibitor in WM115, WM983 and A375 human melanoma cell lines harboring BRAFV600 mutations using Dabrafenib and Trametinib over a course of 9-11 months. The drug resistant cell lines exhibited increased viability and maintenance of downstream p-ERK protein as compared to their drug sensitive counterparts. Receptor tyrosine kinase array revealed an increase in phosphorylated HER3, AXL, EGFR and IGF1R in the drug resistant cells versus drug sensitive cells. Quantitative PCR data revealed an upregulation of these molecules along with an increase in the expression of some of their ligands at the mRNA level. RNA-seq analysis identified IGF1R and IGF2BP2 to be upregulatedin the resistant cell lines compared to parental cell lines.IGF2BP2 is a tumor promoter and drives cancer proliferation in a variety of malignancies and is correlated with poor survival.Our next experiments are focused on testing the efficacy of IGF1R inhibitors in the drug resistant cell lines and their downstream effector signaling molecules in vitro and in vivo. Further, we aim to decipher the mechanism by which IGF2BP2 regulates the IGF1R signaling pathway in MAPK inhibitors resistant melanoma setting. Delineating the role of IGF1R in mediating resistance to BRAF and MEK inhibitors will help expand possible treatment options to aid in long-term success for BRAF-mutant melanoma patients. Citation Format: Hima Patel, Rosalin Mishra, Natasa Broit, Nour Yacoub, Long Yuan, Samar Alanazi, Nicholas Hayward, Peter Johansson, Joan T. Garrett. Role of IGF1R in mediating resistance to MAPK pathway inhibitors in BRAF-mutant melanoma [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1894.

Dissecting Mechanisms of Melanoma Resistance to BRAF and MEK Inhibitors Revealed Genetic and Non-Genetic Patient- and Drug-Specific Alterations and Remarkable Phenotypic Plasticity.

The clinical benefit of MAPK pathway inhibition in BRAF-mutant melanoma patients is limited by the development of acquired resistance. Using drug-naïve cell lines derived from tumor specimens, we established a preclinical model of melanoma resistance to vemurafenib or trametinib to provide insight into resistance mechanisms. Dissecting the mechanisms accompanying the development of resistance, we have shown that (i) most of genetic and non-genetic alterations are triggered in a cell line- and/or drug-specific manner; (ii) several changes previously assigned to the development of resistance are induced as the immediate response to the extent measurable at the bulk levels; (iii) reprogramming observed in cross-resistance experiments and growth factor-dependence restricted by the drug presence indicate that phenotypic plasticity of melanoma cells largely contributes to the sustained resistance. Whole-exome sequencing revealed novel genetic alterations, including a frameshift variant of RBMX found exclusively in phospho-AKThigh resistant cell lines. There was no similar pattern of phenotypic alterations among eleven resistant cell lines, including expression/activity of crucial regulators, such as MITF, AXL, SOX, and NGFR, which suggests that patient-to-patient variability is richer and more nuanced than previously described. This diversity should be considered during the development of new strategies to circumvent the acquired resistance to targeted therapies.

Vemurafenib resistant melanoma cells acquire mesenchymal stem cell-like properties

Background. Activating mutations in the BRAF gene leads to a constitutive activation of the MAPK signaling. The highly selective BRAFV600E inhibitor, vemurafenib, improves the overall survival of BRAF-mutant melanoma patients. However, despite the excellent results of response rate, the average duration of the response was short and acquired resistance develops in most BRAF mutated melanoma patients within a few months. Objective: to derive melanoma cell lines from surgical species of patients with BRAF mutant melanomas resistant to vemurafenib and to elucidate the mechanisms involved in acquired drug resistance.Materials and methods. Mel Ki and Mel F1702 melanoma cells were obtained from metastases of disseminated melanoma patients with BRAFV600E mutation. 2D tumor cell culture, MTT test, immunicytochemistry, flow cytometry, real-time polimerase chain reaction and osteogenic and adipocytic differentiation were used in the study.Results. We have derived two melanoma cell lines Mel Ki and Mel F1702 from tumor samples of patients with BRAFV600E mutation resistant to vemurafenib. These cells were homogenous and had fibroblastic morphology. The IC50 values for Mel Ki and Mel F1702 were 4.7 and 6.3 μM, respectively. The expression of cancer-testis antigens was not detected in both types of cells suggesting the stemness of Mel Ki and Mel F1702 melanoma cells. The immunophenotypic profile of the vemurafenib resistsant melanoma cells showed the expression of typical mesenchymal stem cells markers such as CD90, CD105 and CD44. In addition, we found that the melanoma cell lines derived from tumor resistant to vemurafenib differentiated into osteoblastand adipocyte-like cells. Conclusion. In this study we are offering an experimental evidence of the phenotypic transition of the vemurafenib-resistant melanoma cells into mesenchymal stem-like cells.

Clinical implications of ALDH1A1 and ALDH1A3 mRNA expression in melanoma subtypes

Aldehyde dehydrogenase (ALDH) activity is not only a valuable marker for cancer cells with stem-like features, but also plays a vital role in drug resistance and disease progression in many tumors including melanoma. However, the precise role of ALDH activity in patient prognosis remains unclear. In this study, using the Cancer Genome Atlas (TCGA) RNA-sequencing expression data, we analyzed gene expression of ALDH isozymes in melanoma tumors to define the expression patterns and the prognostic and predictive values of these enzymes. We found that ALDH1A1 and ALDH1A3 had both higher and broader expression ranges in melanoma patients, and that ALDH1A3 expression correlated with better overall survival in metastatic melanoma. Further, stratification of the TCGA cohorts by the mutational subtypes of melanoma specifically revealed that expression of ALDH1A3 correlated with better prognosis in metastatic BRAF-mutant melanoma while expression of ALDH1A1 correlated with better prognosis in BRAF wild-type melanoma. Gene set enrichment analysis (GSEA) of these cohorts identified upregulation in oxidative phosphorylation, adipogenesis, and fatty acid metabolism signaling in ALDH1Alo patients, suggesting BRAF/MEK inhibitor resistance in that subset of patients. On the other hand, GSEA of ALDH1A3hi cohorts revealed upregulation in glycolysis, hypoxia and angiogenesis, suggesting BRAF/MEK inhibitor sensitivity in that subset of patients. Gene expression analysis using pre-treatment tumor samples supports high ALDH1A3 expression before BRAF/MEK inhibitor treatment as predictive of better treatment response in BRAF-mutant melanoma patients. Our study provides evidence that high ALDH1A3 mRNA expression is not only a prognostic marker but also a predictive marker for BRAF/MEK inhibitor treatment response in BRAF-mutant metastatic melanoma patients.

Impact of the Timing of Brain Radiation in Melanoma Patients with BRAF Mutations Who Developed Brain Metastases

With the known intracranial activity of BRAFi, it is unclear in BRAF-mutated melanoma patients with brain metastases whether brain radiation should be given upfront at the time of brain metastasis diagnosis or at the time of progression on BRAFi alone. A total of 102 patients at a single institution with BRAF-mutant melanoma who developed brain metastases were included in this retrospective study. Exclusion criteria included prior BRAFi use, or insufficient follow-up. All patients received BRAFi and brain radiation (WBRT or SRS), and they were separated into 2 groups by chronology of treatment: Group A (n=83) received upfront intracranial radiation (prior to initiation of BRAFi or within <30 days of initiation of BRAFi); and Group B (n=19) received brain radiation for salvage (>30 days after initiation of BRAFi treatment). Kaplan-Meier analysis was used to estimate OS (overall survival) and intracranial PFS (progression free survival, defined as no development of a new or growth of a pre-existing lesion), whereas log-rank testing was used to assess for differences. The median OS of Group A and Group B was 15.5 and 12.4 months, respectively (p = 0.52). There was no difference in the OS between the two groups at 6, 12, 18, or 24 months. There was a trend for better median intracranial PFS for Group A, but this did not reach statistical significance (6.2 vs. 4.4 months, p=0.067). At 6 months the intracranial PFS was significantly better for Group A (60.2% vs 31.6%, p=0.04), but not at 12 months (34.9% vs 10.5%, p=0.051), or 24-month intracranial PFS (31.3% vs 10.5%, p=0.088) This single-institution small retrospective analysis showed that the timing of brain radiation delivered either upfront at the time of BM diagnosis or at the time of salvage for progression in BRAFi, did not impact patient’s OS. Although upfront brain radiation did improve 6-month intracranial PFS compared to delayed radiation, such benefit from upfront brain radiation was lost at later time points. A larger, multi-institutional retrospective review or a prospective study is needed to further tease out the significance of the timing of brain radiation in this patient population.

The Benefit of Reactivating p53 under MAPK Inhibition on the Efficacy of Radiotherapy in Melanoma.

Radiotherapy (RT) in patients with melanoma historically showed suboptimal results, because the disease is often radioresistant due to various mechanisms such as scavenging free radicals by thiols, pigmentary machinery, or enhanced DNA repair. However, radiotherapy has been utilized as adjuvant therapy after the complete excision of primary melanoma and lymph nodes to reduce the rate of nodal recurrences in high-risk patients. The resistance of melanoma cells to radiotherapy may also be in relation with the constitutive activation of the MAPK pathway and/or with the inactivation of p53 observed in about 90% of melanomas. In this study, we aimed to assess the potential benefit of adding RT to BRAF-mutated melanoma cells under a combined p53 reactivation and MAPK inhibition in vitro and in a preclinical animal model. We found that the combination of BRAF inhibition (vemurafenib, which completely shuts down the MAPK pathway), together with p53 reactivation (PRIMA-1Met) significantly enhanced the radiosensitivity of BRAF-mutant melanoma cells. This was accompanied by an increase in both p53 expression and activity. Of note, we found that radiation alone markedly promoted both ERK and AKT phosphorylation, thus contributing to radioresistance. The combination of vemurafenib and PRIMA-1Met caused the inactivation of both MAPK kinase and PI3K/AKT pathways. Furthermore, when combined with radiotherapy, it was able to significantly enhance melanoma cell radiosensitivity. Interestingly, in nude mice bearing melanoma xenografts, the latter triple combination had not only a synergistic effect on tumor growth inhibition, but also a potent control on tumor regrowth in all animals after finishing the triple combination therapy. RT alone had only a weak effect. In conclusion, we provide a basis for a strategy that may overcome the radioresistance of BRAF-mutated melanoma cells to radiotherapy. Whether this will translate into a rational to use radiotherapy in the curative setting in BRAF-mutated melanoma patients deserves consideration.