Impaired NK cell recognition of vemurafenib-treated melanoma cells is overcome by simultaneous application of histone deacetylase inhibitors

Abstract

Therapy of metastatic melanoma advanced recently with the clinical implementation of signalling pathway inhibitors, such as vemurafenib, specifically targeting mutant BRAF. In general, patients experience remarkable clinical responses under BRAF inhibitor (BRAFi) treatment but eventually progress within 6-8 months due to resistance development. Responding metastases show an increased immune cell infiltrate, including also NK cells, that, however, is no longer detectable in BRAFi-resistant lesions, suggesting NK cell activity should be exploited to prevent disease progression. Here, we examined the effects of BRAFi on the expression of ligands targeting activating NK cells receptors immediately after treatment onset, prior to resistance development. We demonstrate that BRAF mutant melanoma cells cultured in the presence of vemurafenib, strongly decreased surface expression of ligands for NK activating receptors including the NKG2D-ligand, MICA, and the DNAM-1 ligand, CD155, and became significantly less susceptible to NK cell attack. NKG2D-ligand protein downregulation was due to a significant decrease in mRNA levels, already detectable 24 h after drug treatment. Interestingly, vemurafenib-induced MICA downregulation could be counteracted by treatment of melanoma cells with the histone deacetylase (HDAC) inhibitor (HDACi) sodium butyrate, that also upregulated the DNAM1-ligand, Nectin-2. HDACi treatment enhanced surface expression of NKG2D-ligands in the presence of BRAFi, accompanied by recovery of NK cell recognition, but only upon simultaneous drug application. These results suggest that co-administration of BRAFi and HDAC inhibitors as well as having direct effects on melanoma cell survival, could also synergise to improve NK cell recognition and avoid tumour immune evasion.

HO‐1 downregulation favors BRAFV600 melanoma cell death induced by Vemurafenib/PLX4032 and increases NK recognition

“…20 However, a direct inhibitory effect of PLX4032 on NK functions is unlikely, since BRAFis per se could not modify the NK cell phenotype, 4,36 and instead increased NK number were detected in peripheral blood, as shown in PLX4032-treated patients. In fact, an impaired cytotoxic activity of NK cells has been correlated to melanoma relapse and progression.…”

“…In line with our results, it has been demonstrated that HO-1 is involved in the regulation of PD-L1 expression in renal cancer cells and its induction contributes to immuneescape. 20 They also showed that melanoma cell exposure to histone deacetylase inhibitors, known for their ability to increase the expression of ligands for NK activator receptors, 40 restored NK-mediated killing. It is conceivable that an important mediator of the immunomodulatory effect of HO-1 is CO.…”

“…20,21 Along this line, we analyzed cytokine-activated NK cells for their ability to undergo degranulation in the presence of MeOV-1 melanoma cell line either untreated (DMSO) or treated with PLX4032 (1 μM) for 24 hr. 20,21 Along this line, we analyzed cytokine-activated NK cells for their ability to undergo degranulation in the presence of MeOV-1 melanoma cell line either untreated (DMSO) or treated with PLX4032 (1 μM) for 24 hr.…”

Epigenetic priming of both tumor and NK cells augments antibody-dependent cellular cytotoxicity elicited by the anti-PD-L1 antibody avelumab against multiple carcinoma cell types

“…Furthermore, these results are in agreement with what other reports have shown for entinostat, vorinostat, and other HDAC inhibitors (sodium butyrate and sodium valproate) in other tumor types. 22,51–54 One study found that hepatocellular carcinoma cells treated with sodium valproate had increased recognition by cytotoxic lymphocytes in an NKG2D-dependent manner, and increased the expression of MIC-A/B on these cells. 54 Another study reported that treatment of DAOY (medulloblastoma) and PC-3 cells with multiple HDAC inhibitors resulted in elevated expression of MIC-A/B, ULBP1-3, CD112, and CD155, and enhanced lysis of these cells by IL-2‒activated PBMCs.…”

“…22,51–54 Our study simultaneously investigated tumor cell lines from NSCL, SCL, prostate, TNB, and ovarian origins, extending the effect of HDAC inhibition enhancing NK killing to novel tumor types. Additionally, our study provided a more comprehensive analysis of 12 different NK lysis relevant proteins on the surface of nine different cell lines encompassing five different tumor types (Tables 1 and 3, Supplemental Tables 1 and 2).…”