Potential Biomarkers of Skin Melanoma Resistance to Targeted Therapy—Present State and Perspectives

Melanoma genomics - will we go beyond BRAF in clinics?

In the era of next-generation sequencing, the genetic background of cancer, including melanoma, appears to be thoroughly established. However, evaluating the oncogene BRAF mutation in codon V600 is still the only companion diagnostic genomic test commonly implemented in clinics for molecularly targeted treatment of advanced melanoma. Are we wasting the collected genomic data? Will we implement our current genomic knowledge of melanoma in clinics soon? This question is rather urgent because new therapeutic targets and biomarkers are needed to implement more personalized, patient-tailored therapy in clinics. Here, we provide an update on the molecular background of melanoma, including a description of four already established molecular subtypes: BRAF+, NRAS+, NF1+, and triple WT, as well as relatively new NGS-derived melanoma genes such as PREX2, ERBB4, PPP6C, FBXW7, PIK3CA, and IDH1. We also present a comparison of genomic profiles obtained in recent years with a focus on the most common melanoma genes. Finally, we propose our melanoma gene panel consisting of 22 genes that, in our opinion, are "must-have" genes in both melanoma-specific genomic tests and pan-cancer tests established to improve the treatment of melanoma further.

Multi-omics analysis delineates resistance mechanisms associated with BRAF inhibition in melanoma cells

Mutant BRAF is a critical oncogenic driver in melanoma, making it an attractive therapeutic target. However, the success of targeted therapy using BRAF inhibitors vemurafenib and dabrafenib has been limited due to development of resistance, restricting their clinical efficacy. A prior knowledge of resistance mechanisms to BRAFi or any cancer drug can lead to development of drugs that overcome resistance thus improving clinical outcomes. In vitro cellular models are powerful systems that can be utilized to mimic and study resistance mechanisms. In this study, we employed a multi-omics approach to characterize a panel of BRAF mutant melanoma cell lines to develop and systematically characterize BRAFi persister and resistant cells using exome sequencing, proteomics and phosphoproteomics. Our datasets revealed frequently observed intrinsic and acquired, genetic and non-genetic mechanisms of BRAFi resistance that have been studied in patients who developed resistance. In addition, we identified proteins that can be potentially targeted to overcome BRAFi resistance. Overall, we demonstrate that in vitro systems can be utilized not only to predict resistance mechanisms but also to identify putative therapeutic targets.

Unveiling the Dynamic Interplay between Cancer Stem Cells and the Tumor Microenvironment in Melanoma: Implications for Novel Therapeutic Strategies

Cutaneous melanoma still represents a significant health burden worldwide, being responsible for the majority of skin cancer deaths. Key advances in therapeutic strategies have significantly improved patient outcomes; however, most patients experience drug resistance and tumor relapse. Cancer stem cells (CSCs) are a small subpopulation of cells in different tumors, including melanoma, endowed with distinctive capacities of self-renewal and differentiation into bulk tumor cells. Melanoma CSCs are characterized by the expression of specific biomarkers and intracellular pathways; moreover, they play a pivotal role in tumor onset, progression and drug resistance. In recent years, great efforts have been made to dissect the molecular mechanisms underlying the protumor activities of melanoma CSCs to provide the basis for novel CSC-targeted therapies. Herein, we highlight the intricate crosstalk between melanoma CSCs and bystander cells in the tumor microenvironment (TME), including immune cells, endothelial cells and cancer-associated fibroblasts (CAFs), and its role in melanoma progression. Specifically, we discuss the peculiar capacities of melanoma CSCs to escape the host immune surveillance, to recruit immunosuppressive cells and to educate immune cells toward an immunosuppressive and protumor phenotype. We also address currently investigated CSC-targeted strategies that could pave the way for new promising therapeutic approaches for melanoma care.

Review of the application of the most current sophisticated image processing methods for the skin cancer diagnostics purposes

This paper presents the most current and innovative solutions applying modern digital image processing methods for the purpose of skin cancer diagnostics. Skin cancer is one of the most common types of cancers. It is said that in the USA only, one in five people will develop skin cancer and this trend is constantly increasing. Implementation of new, non-invasive methods plays a crucial role in both identification and prevention of skin cancer occurrence. Early diagnosis and treatment are needed in order to decrease the number of deaths due to this disease. This paper also contains some information regarding the most common skin cancer types, mortality and epidemiological data for Poland, Europe, Canada and the USA. It also covers the most efficient and modern image recognition methods based on the artificial intelligence applied currently for diagnostics purposes. In this work, both professional, sophisticated as well as inexpensive solutions were presented. This paper is a review paper and covers the period of 2017 and 2022 when it comes to solutions and statistics. The authors decided to focus on the latest data, mostly due to the rapid technology development and increased number of new methods, which positively affects diagnosis and prognosis.

ATP1A1 is a promising new target for melanoma treatment and can be inhibited by its physiological ligand bufalin to restore targeted therapy efficacy

Despite advancements in treating metastatic melanoma, many patients exhibit resistance to targeted therapies. Our study focuses on ATP1A1, a sodium pump subunit associated with cancer development. We aimed to assess ATP1A1 prognostic value in melanoma patients and examine the impact of its ligand, bufalin, on melanoma cell lines in vitro and in vivo. High ATP1A1 expression (IHC) correlated with reduced overall survival in melanoma patients. Resistance to BRAF inhibitor was linked to elevated ATP1A1 levels in patient biopsies (IHC, qPCR) and cell lines (Western blot, qPCR). Additionally, high ATP1A1 mRNA expression positively correlated with differentiation/pigmentation markers based on data from The Cancer Genome Atlas (TCGA) databases and Verfaillie proliferative gene signature analysis. Bufalin specifically targeted ATP1A1 in caveolae, (proximity ligation assay) and influenced Src phosphorylation (Western blot), thereby disrupting multiple signaling pathways (phosphokinase array). In vitro, bufalin induced apoptosis in melanoma cell lines by acting on ATP1A1 (siRNA experiments) and, in vivo, significantly impeded melanoma growth using a nude mouse xenograft model with continuous bufalin delivery via an osmotic pump. In conclusion, our study demonstrates that ATP1A1 could serve as a prognostic marker for patient survival and a predictive marker for response to BRAF inhibitor therapy. By targeting ATP1A1, bufalin inhibited cell proliferation, induced apoptosis in vitro, and effectively suppressed tumor development in mice. Thus, our findings strongly support ATP1A1 as a promising therapeutic target, with bufalin as a potential agent to disrupt its tumor-promoting activity.

Primary Undifferentiated/Dedifferentiated Cutaneous Melanomas-A Review on Histological, Immunohistochemical, and Molecular Features with Emphasis on Prognosis and Treatment

Diagnosing cutaneous melanoma is usually straightforward based on these malignancies' histopathological and immunohistochemical features. Nevertheless, melanomas can imitate various other neoplasms, sometimes lacking the expression of conventional melanocytic markers and expressing non-melanocytic ones. Furthermore, divergent differentiation is more often encountered in metastatic melanomas and is still poorly described in primary cutaneous melanomas, and little is known about these patients' prognosis and therapeutic approach. Therefore, we reviewed the literature on undifferentiated/dedifferentiated cutaneous melanomas, and we discuss the histological, immunohistochemical, and molecular profiles of undifferentiated/dedifferentiated cutaneous melanomas to understand these peculiar lesions better and improve their diagnostic algorithm. In addition to this, we also discuss how different genetic mutations may influence prognosis and become potential therapeutic targets.

Deciphering the molecular mechanism of enhanced tumor activity of the EGFR variant T790M/L858R using melanoma cell lines

Introduction

The abnormal expression and mutagenesis of EGFR drives both the development and progression of a multitude of human cancers. Further mutations within the tyrosine kinase region of the EGFR subsequently contribute to resistance to targeted drugs. What is not known is how these mutations affect progression-related behaviors of cancer cells.

Methods

The mutagenesis of EGFR T790M, L858R, and T790M/L858R was performed via oligo primer-guided polymerase chain reaction (PCR). GFP-tagged mammalian expression vectors were constructed and confirmed. Stable melanoma cell lines WM983A and WM983B expressing WT or mutant EGFRs were generated for determining the functions of WT and mutant EGFRs in migration, invasion, and resistance to doxorubicin. Immunoblotting and immunofluorescence were performed to detect the transphosphorylation and autophosphorylation of WT and mutant EGFRs and other molecules.

Results

The EGFR mutant T790M/L858R showed significantly higher basal autophosphorylation in melanoma cell lines WM983A and WM983B. Overexpression of WT EGFR significantly enhanced the protein level of E-cadherin (E-cad) via upregulating its mRNA. In contrast, L858R significantly downregulated E-cad. Biological activity assays show that T790M/L858R presented significant enhancement in vitro in invasion and migration, while WT and T790M moderately inhibited invasion and migration. In WM983A cells, enhanced invasion and migration by T790M/L858R required the downstream signaling pathways through Akt and p38. T790M/L858R dramatically triggers phosphorylation of actin cross-linking protein alpha-actinin-4 in the absence of EGF. This double mutant also conferred resistance to a general chemotherapy doxorubicin through Akt but not the p38 signaling pathway.

Conclusion

These findings suggest that T790M/L858R not only confers enhanced therapeutic resistance in cancer cell lines but also may promote tumor metastasis via its boosted downstream signaling pathways and/or direct phosphorylation of other key proteins.