T-type calcium channel inhibition restores sensitivity to MAPK inhibitors in de-differentiated and adaptive melanoma cells

Abstract

BACKGROUND: Drug resistance remains as one of the major challenges in melanoma therapy. It is well known that tumour cells undergo phenotypic switching during melanoma progression, increasing melanoma plasticity and resistance to mitogen-activated protein kinase inhibitors (MAPKi). METHODS: We investigated the melanoma phenotype switching using a partial reprogramming model to de-differentiate murine melanoma cells and target melanoma therapy adaptation against MAPKi. RESULTS: Here, we show that partially reprogrammed cells are a less proliferative and more de-differentiated cell population, expressing a gene signature for stemness and suppressing melanocyte-specific markers. To investigate adaptation to MAPKi, cells were exposed to B-Raf Proto-Oncogene (BRAF) and mitogen-activated protein kinase kinase (MEK) inhibitors. De-differentiated cells became less sensitive to MAPKi, showed increased cell viability and decreased apoptosis. Furthermore, T-type calcium channels expression increased in adaptive murine cells and in human adaptive melanoma cells. Treatment with the calcium channel blocker mibefradil induced cell death, differentiation and susceptibility to MAPKi in vitro and in vivo. CONCLUSION: In summary, we show that partial reprogramming of melanoma cells induces de-differentiation and adaptation to MAPKi. Moreover, we postulated a calcium channel blocker such as mibefradil, as a potential candidate to restore sensitivity to MAPKi in adaptive melanoma cells.

The rise of T-type channels in melanoma progression and chemotherapeutic resistance

“…This was directly demonstrated in patient cohorts by in silico genomic analysis of The Cancer Genome Atlas (TCGA) database, which revealed that the upregulation of Cav3.1 or Cav3.2 isoforms were strongly associated to poor outcomes in Kaplan-Meier estimates [16]. Likewise, a TGCA analysis performed by Granados and colleagues demonstrated that melanoma patients with tumors displaying a higher expression of Cav3.2 have a worse survival, although Cav3.1 was neglected from this study [23]. Table 1 summarizes the reported relationships between the expression of TTCCs isoforms, associations with prognosis markers and effects of specific gene silencing.…”

“…However, the analysis of Cav3.2 transcripts in these conditions was not performed. Another recent article reported that TTCC expression was upregulated in partially reprogrammed (by transduction of genes encoding pluripotency factors) BRAF and NRAS mutant-melanoma cells, acquiring features of stemness, slower proliferation and enhanced invasivity [23]. De-differentiated cells increased the expression of transcripts for Cav3.2 (particularly the NRAS mutants), in agreement with its known role in stemness, although the analysis of Cav3.1 transcripts was omitted.…”

“…Co-administration of mibefradil delayed the growth of vemurafenib-sensitive and resistant cell line-derived xenografts, when compared to either untreated mice or mice treated with only vemurafenib. Similarly, Granados and colleagues orally administered vemurafenib and/or mibefradil to immunodeficient NSG xenografted mice: both drugs synergized in two sequential applications for up to 20 days, to slow tumor growth and extend the survival of xenografted mice in Kaplan-Meier estimates [23]. The role of TTCCs in melanoma motility and invasivity has also been under scrutiny.…”

Role of hydrogen sulfide donors in cancer development and progression

“…It has been revealed that the treatment of HEK293 cells with 1 µM-1 mM NaHS inhibits voltage-gated T-type specifically Cav3.2 channels by promoting extracellular binding of zinc (Zn 2+ ) [46]. At the downstream, the suppression of T-type channels can result in enhanced antitumor activities and improved sensitivity of cancer cells to drugs [47][48][49]. Studies also show that H 2 S donors can trigger the activation of cellular transporters including ATP-binding cassette transporter A1 (ABCA1) [40] and glutamine transporter-1 (GLT-1) [50] by promoting nuclear translocation of peroxisome-proliferator-activated receptor alpha and inhibiting the extracellular signal-regulated kinase 1/2 (ERK 1/2) respectively.…”

Cellular Reprogramming—A Model for Melanoma Cellular Plasticity

“…A downregulation of MITF in melanoma cells has been related to an invasive/poorly proliferative phenotype, increased plasticity and acquired therapy resistance to BRAF inhibition [83][84][85]. Induction of phenotype switching towards a more dedifferentiated state drastically enhances the aggressiveness of the tumor, and constitutes an essential mechanism underlying therapy resistance in melanoma patients [2,86,87].…”