The transcription factor RUNX2 regulates receptor tyrosine kinase expression in melanoma

Abstract

Receptor tyrosine kinases-based autocrine loops largely contribute to activate the MAPK and PI3K/AKT pathways in melanoma. However, the molecular mechanisms involved in generating these autocrine loops are still largely unknown. In the present study, we examine the role of the transcription factor RUNX2 in the regulation of receptor tyrosine kinase (RTK) expression in melanoma. We have demonstrated that RUNX2-deficient melanoma cells display a significant decrease in three receptor tyrosine kinases, EGFR, IGF-1R and PDGFRβ. In addition, we found co-expression of RUNX2 and another RTK, AXL, in both melanoma cells and melanoma patient samples. We observed a decrease in phosphoAKT2 (S474) and phosphoAKT (T308) levels when RUNX2 knock down resulted in significant RTK down regulation. Finally, we showed a dramatic up regulation of RUNX2 expression with concomitant up-regulation of EGFR, IGF-1R and AXL in melanoma cells resistant to the BRAF V600E inhibitor PLX4720. Taken together, our results strongly suggest that RUNX2 might be a key player in RTK-based autocrine loops and a mediator of resistance to BRAF V600E inhibitors involving RTK up regulation in melanoma.

Transcription factors as critical players in melanoma invasiveness, drug resistance, and opportunities for therapeutic drug development

“…Interestingly, RUNX2 physically and functionally interacts with HIF1‐α (Kwon et al., ; Lee et al., ) and RUNX2 stabilizes HIF1‐α under normoxic conditions (Lee et al., ). As mentioned earlier, RUNX2 overexpression in melanoma has been associated with acquired resistance to BRAFi (Anastas et al., ; Boregowda et al., ). Therefore, in addition to increasing RTK expression and promoting migration and invasion (Boregowda et al., ), another mechanism through which RUNX2 might promote resistance would involve HIF‐1α stabilization.…”

“…We previously demonstrated that RUNX2‐deficient melanoma cells displayed a significant decrease in four receptor tyrosine kinases, EGFR, IGF‐1R, PDGFRβ, and AXL, and strongly suggested a role for RUNX2 as a key player in mediating intrinsic RTK‐associated pro‐oncogenic properties in melanoma. In addition, we showed a dramatic upregulation of RUNX2 expression with concomitant upregulation of EGFR, IGF‐1R, and AXL in melanoma cells rendered resistant to PLX4720 (Boregowda et al., ). We then reported that PLX4720‐resistant cells developed in an in vivo context exhibit an increase in RUNX2 levels when re‐exposed to PLX4720 in vitro.…”

“…The expression of RUNX2 isoform 3 was significantly higher in vemurafenib‐treated patients compared to the untreated group. These results showing the upregulation of RUNX2 in melanoma lesions from patients treated with vemurafenib suggest that chronic exposure to BRAFi (PLX4720/vemurafenib) may favor RUNX2 upregulation and subsequent RTK upregulation, an important player in acquired resistance to these drugs (Boregowda et al., ).…”

“…One possible mechanism would involve WNT5A and the WNT5A‐mediated activation of the PI3K/AKT pathway (Anastas et al., ). As RUNX2 expression is increased by the PI3K/AKT pathway signaling (Boregowda et al., ; Cohen‐Solal, Boregowda, & Lasfar, ), elevated WNT5A expression and subsequent AKT pathway activation could result in RUNX2 overexpression. Therefore, any kinase rewiring that leads to hyperactivated PI3K/AKT signaling in melanomas resistant to BRAFi (Paraiso et al., ) would provide a favorable context for high RUNX2 expression.…”

The AP-1 complex regulates AXL expression and determines sensitivity to PI3Kα inhibition in esophagus and head and neck squamous cell carcinoma

“…A number of studies have shown that overexpression of AXL in response to therapeutic stress can evolve through a variety of mechanisms, including transcriptional regulation (15,23,24,(50)(51)(52), post-translational regulation (53,54), and expression of miRNA (55) [reviewed in (56) Additionally, blocking AP-1 transcription activity may serve to influence the expression of key RTKs, such as EGFR (62,63), and/or to reduce the expression of the immuno-suppressor modulator of programmed cell death ligand 1 (PD-L1) (64), and hence enhance tumor elimination. The latter possibility is also supported by the findings that AXL and PD-L1 expression are correlated in different cancers (65,66), and in the cancer genome atlas (TCGA) data set for head and neck cancer (data not shown).…”