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Background/Objectives: The fat mass and obesity-associated (FTO) protein demethylates nuclear N6-Methyladenosine (m6A) on mRNA, facilitates tumor growth, and contributes to therapeutic resistance in multiple cancer types. Recent evidence demonstrates several roles of FTO in tumorigenesis. In this study, we seek to explore the role of FTO in non-small cell lung cancer (NSCLC) tumorigenicity and its relationship with epidermal growth factor receptor (EGFR) tyrosine kinase resistance. Methods: We performed qPCR, immunoblotting, viability assays, migration assays, and ATP assays to investigate the functions of FTO in EGFR tyrosine kinase inhibitor (TKI) resistance, specifically to erlotinib, in three NSCLC cell lines harboring either wild-type or mutant EGFR. We also performed immunohistochemistry on lung tumor tissues from patients diagnosed at different stages of NSCLC. Results: Our study found an upregulation of FTO in erlotinib-resistant (ER) cell lines at both the gene and protein levels. FTO inhibition and knockdown significantly reduced cell viability of erlotinib-resistant H2170 and PC9 cells by over 30% when treated with 0.8 µM of Dac51 and about 20% when treated with siFTO. FTO inhibition also slowed down the migration of ER cells, and the effect was even more pronounced when combined with erlotinib. Furthermore, FTO was found to be overexpressed in late-stage NSCLC tumor tissues compared to early-stage tumors, and it was upregulated in patients who smoked. Conclusions: These findings suggest FTO might mediate resistance and tumor growth by augmenting cell proliferation. In addition, FTO can be a potential prognostic marker in NSCLC patients.

NSCLC treatment includes targeting of EGFR with tyrosine kinase inhibitors (TKIs) such as Erlotinib; however, resistance to TKIs is commonly acquired through T790M EGFR mutations or overexpression of vascular endothelial growth factor receptor-2 (VEGFR-2). We investigated the mechanisms of EGFR-TKI resistance in NSCLC cell lines with EGFR mutations or acquired resistance to Erlotinib. These studies showed upregulated gene and protein expression of VEGF, VEGFR-2, and a VEGF co-receptor neuropilin-1 (NP-1) in Erlotinib-resistant (1.4–5.3-fold) and EGFR double-mutant (L858R and T790M; 4.1–8.3-fold) NSCLC cells compared to parental and EGFR single-mutant (L858R) NSCLC cell lines, respectively. Immunofluorescence and FACS analysis revealed increased expression of VEGFR-2 and NP-1 in EGFR-TKI-resistant cell lines compared to TKI-sensitive cell lines. Cell proliferation assays showed that treatment with a VEGFR-2 inhibitor combined with Erlotinib lowered cell survival in EGFR double-mutant NSCLC cells to 9% compared to 72% after treatment with Erlotinib alone. Furthermore, Kaplan–Meier analysis revealed shorter median survival in late-stage NSCLC patients with high vs. low VEGFR-2 expression (14 mos vs. 21 mos). The results indicate that VEGFR-2 may play a key role in EGFR-TKI resistance and that combined treatment of Erlotinib with a VEGFR-2 inhibitor may serve as an effective therapy in NSCLC patients with EGFR mutations.

Melanoma possesses invasive metastatic growth patterns and is one of the most aggressive types of skin cancer. In 2021, it is estimated that 7180 deaths were attributed to melanoma in the United States alone. Once melanoma metastasizes, traditional therapies are no longer effective. Instead, immunotherapies, such as ipilimumab, pembrolizumab, and nivolumab, are the treatment options for malignant melanoma. Several biomarkers involved in tumorigenesis have been identified as potential targets for molecularly targeted melanoma therapy, such as tyrosine kinase inhibitors (TKIs). Unfortunately, melanoma quickly acquires resistance to these molecularly targeted therapies. To bypass resistance, combination treatment with immunotherapies and single or multiple TKIs have been employed and have been shown to improve the prognosis of melanoma patients compared to monotherapy. This review discusses several combination therapies that target melanoma biomarkers, such as BRAF, MEK, RAS, c-KIT, VEGFR, c-MET and PI3K. Several of these regimens are already FDA-approved for treating metastatic melanoma, while others are still in clinical trials. Continued research into the causes of resistance and factors influencing the efficacy of these combination treatments, such as specific mutations in oncogenic proteins, may further improve the effectiveness of combination therapies, providing a better prognosis for melanoma patients.