Combinatorial Therapies to Overcome BRAF/MEK Inhibitors Resistance in Melanoma Cells: An in vitro Study

BRAFV600E/p-ERK/p-DRP1(Ser616) Promotes Tumor Progression and Reprogramming of Glucose Metabolism in Papillary Thyroid Cancer

Background: Papillary thyroid cancer (PTC) with the BRAFV600E mutation is associated with a poorer prognosis. BRAF inhibitors may demonstrate limited efficacy due to emerging drug resistance. The Warburg effect may have cancer therapeutic implications. It is not known if the BRAFV600E mutation is associated with altered glucose metabolism in PTC. Methods: This study examined the effect of BRAFV600E and dynamin-related protein 1 (DRP1) on various cellular processes in PTC cells, including cell proliferation, migration, invasion, mitochondrial fission, glucose metabolism, reactive oxygen species (ROS) generation, and apoptosis. We used RT-qPCR to assess the expression of key glycolytic enzymes in thyroid cancer tissues. Additionally, the regulatory interaction between BRAFV600E and DRP1 was investigated through Western blot and immunohistochemical staining. We further evaluated the impact of DRP1 in PTC and the inhibitory effects of dabrafenib and 2-deoxy-d-glucose (2-DG) in vitro and in vivo. Results: We found that the BRAFV600E mutation significantly augments aerobic glycolysis while suppressing oxidative phosphorylation in PTC. We identified the BRAFV600E/p-ERK/p-DRP1(Ser616) signaling pathway as a critical mediator in PTC progression. First, the BRAFV600E/p-ERK/p-DRP1(Ser616) signaling pathway enhances cell proliferation by upregulating hexokinase 2 expression and thereby increasing aerobic glycolysis. Second, it inhibits apoptosis by promoting mitochondrial fission and reducing ROS levels. Moreover, we demonstrated that the combination therapy of 2-DG and dabrafenib markedly impedes the progression of BRAFV600E-positive PTC. Conclusion: The BRAFV600E/p-ERK/p-DRP1(Ser616) signaling pathway plays a pivotal role in glucose metabolism reprogramming, contributing to the aggressiveness and progression of BRAFV600E-positive PTC. Our findings suggest that a combined therapeutic approach using 2-DG and dabrafenib has the potential to improve the outcome of PTC patients with BRAFV600E.

In Vitro Experiments on the Effects of GP-2250 on BRAF-Mutated Melanoma Cell Lines and Benign Melanocytes

Enhanced glycolysis (Warburg effect) driven by the BRAF oncogene, dysregulated GAPDH expression, and activation of the PI3K/AKT/mTOR signaling pathway may significantly contribute to the resistance-targeted therapy of BRAF-mutated melanomas. Therefore, we aimed to study for the first time the anti-tumor activity of the GAPDH inhibitor GP-2250 in BRAF-mutated melanoma cell lines and benign melanocytes. We employed three melanoma cell lines and one primary melanocyte cell line (Ma-Mel-61a, Ma-Mel-86a, SH-4 and ATCC-PCS-200-013, respectively), which were exposed to different GP-2250 doses. GP-2250's effects on cell proliferation and viability were evaluated by means of the BrdU and MTT assays, respectively. The RealTime-Glo Annexin V Apoptosis and Necrosis Assay was performed for the evaluation of apoptosis and necrosis induction. RT-PCR and western blotting were implemented for the determination of AKT and STAT3 gene and protein expression analyses, respectively. The melanoma cell lines showed a dose-dependent response to GP-2250 during BrDU and MTT testing. The RealTime-Glo Annexin V assay revealed the heterogenous impact of GP-2250 on apoptosis as well as necrosis. With respect to the melanoma cell lines Ma-Mel-86a and SH-4, the responses and dosages were comparable to those used for the MTT viability assay. Using the same dose range of GP-2250 administered to melanoma cells, however, we observed neither the noteworthy apoptosis nor necrosis of GP-2250-treated benign melanocytes. The gene expression profiles in the melanoma cell lines for AKT and STAT3 were heterogenous, whereby AKT as well as STAT3 gene expression were most effectively downregulated using the highest GP-2250 doses. Immunoblotting revealed that there was a time-dependent decrease in protein expression at the highest GP-2250 dose used, whereas a time- as well as dose-dependent AKT decrease was predominantly observed in Ma-Mel-61a. The STAT3 protein expression of Ma-Mel-86a and SH-4 was reduced in a time-dependent pattern at lower and moderate doses. STAT3 expression in Ma-Me-61a was barely altered by GP-2250. In conclusion, GP-2250 has anti-neoplastic effects in BRAF-mutated melanoma cell lines regarding tumor cell viability, proliferation, and apoptosis/necrosis. GP-2250 is able to downregulate the gene and protein expression of aberrant tumorigenic pathways in melanoma cell lines. Since GP-2250 is a GAPDH inhibitor, the substance may be a promising combination therapy for tumors presenting the Warburg effect, such as melanoma.

Advancements in melanoma cancer metastasis models

Metastatic melanoma is a complex and deadly disease. Due to its complexity, the development of novel therapeutic strategies to inhibit metastatic melanoma remains an outstanding challenge. Our ability to study metastasis is advanced with the development of in vitro and in vivo models that better mimic the different steps of the metastatic cascade beginning from primary tumor initiation to final metastatic seeding. In this review, we provide a comprehensive summary of in vitro models, in vivo models, and in silico platforms to study the individual steps of melanoma metastasis. Furthermore, we highlight the advantages and limitations of each model and discuss the challenges of how to improve current models to enhance translation for melanoma cancer patients and future therapies.

Warburg and pasteur phenotypes modulate cancer behavior and therapy

Energetic pathways combine in the heart of metabolism. These essential routes supply energy for biochemical processes through glycolysis and oxidative phosphorylation. Moreover, they support the synthesis of various biomolecules employed in growth and survival over branching pathways. Yet, cellular energetics are often misguided in cancers as a result of the mutations and altered signaling. As nontransformed and Pasteur-like cells metabolize glucose through oxidative respiration when only oxygen is sufficient, some cancer cells bypass this metabolic switch and run glycolysis at higher rates even in the presence of oxygen. The phenomenon is called aerobic glycolysis or the Warburg effect. An increasing number of studies indicate that both Warburg and Pasteur phenotypes are recognized in the cancer microenvironment and take vital roles in the regulation of drug resistance mechanisms such as redox homeostasis, apoptosis and autophagy. Therefore, the different phenotypes call for different therapeutic approaches. Combined therapies targeting energy metabolism grant new opportunities to overcome the challenges. Nevertheless, new biomarkers emerge to classify the energetic subtypes, thereby the cancer therapy, as our knowledge in coupling energy metabolism with cancer behavior grows.