The HDAC inhibitor AR42 interacts with pazopanib to kill trametinib/dabrafenib-resistant melanoma cells in vitro and in vivo

Abstract

Studies focused on the killing of activated B-RAF melanoma cells by the histone deacetylase (HDAC) inhibitor AR42. Compared to other tumor cell lines, PDX melanoma isolates were significantly more sensitive to AR42-induced killing. AR42 and the multi-kinase inhibitor pazopanib interacted to activate: an eIF2α–Beclin1 pathway causing autophagosome formation; an eIF2α–DR4/DR5/CD95 pathway; and an eIF2α-dependent reduction in the expression of c-FLIP-s, MCL-1 and BCL-XL. AR42 did not alter basal chaperone activity but increased the ability of pazopanib to inhibit HSP90, HSP70 and GRP78. AR42 and pazopanib caused HSP90/HSP70 dissociation from RAF-1 and B-RAF that resulted in reduced ‘RAF’ expression. The drug combination activated a DNA-damage-ATM-AMPK pathway that was associated with: NFκB activation; reduced mTOR S2448 and ULK-1 S757 phosphorylation; and increased ULK-1 S317 and ATG13 S318 phosphorylation. Knock down of PERK, eIF2α, Beclin1, ATG5 or AMPKα, or expression of IκB S32A S36A, ca-mTOR or TRX, reduced cell killing. AR42, via lysosomal degradation, reduced the protein expression of HDACs 2/5/6/10/11. In vivo, a 3-day exposure of dabrafenib/trametinib resistant melanoma cells to the AR42 pazopanib combination reduced tumor growth and enhanced survival from ∼25 to ∼40 days. Tumor cells that had adapted through therapy exhibited elevated HGF expression and the c-MET inhibitor crizotinib enhanced AR42 pazopanib lethality in this evolved drug-resistant population.

Prior exposure of pancreatic tumors to [sorafenib + vorinostat] enhances the efficacy of an anti-PD-1 antibody

“…The levels of CCL2 did not alter and those of CCL5 declined; the levels of the chemokines CCL2 and CCL5 were increased which would predict for macrophage invasion and activation. 16 In recent melanoma studies, in the plasma from animals exposed to [HDAC inhibitor + anti-PD-1], HDAC exposure also increased the levels of IL-12 and reduced the levels of IL-10, TGFβ and IL-1α, again in agreement with the presence of M1, but not M2, macrophages in the tumor. And as we have observed in our present pancreatic cancer work, the cytokine data from HDAC inhibitor plus anti-PD-1 exposed melanoma tumors correlated with increased activated T cell, M1 macrophage, neutrophil and NK cell infiltration.…”

“…PD-L1, MHCA, ODC and IDO-1. [16][17][18][19] Our prior studies with sorafenib and vorinostat in hepatoma cells had argued that the drug-induced formation of autophagosomes was partially protective against drug combination lethality. However, the role of autophagy regulating cell survival in pancreatic cancer cells expressing mutated K-RAS proteins is unknown.…”

The CHK1 inhibitor SRA737 synergizes with PARP1 inhibitors to kill carcinoma cells

“…Recent prior studies from our group have demonstrated how the PDE5 inhibitor sildenafil (Viagra) can enhance the DNA damage response activation of ATM by pemetrexed or an HDAC inhibitor. 19,20 Sildenafil causes the tumor cells to generate nitric oxide, which reacts with tumor cell ROS to elevate the levels of peroxy-nitrate. Peroxy-nitrate is a potent inhibitor of protein phosphatases that inactivate ATM and PERK/eIF2α, i.e.…”

Cancer Stem Cells: Devil or Savior—Looking behind the Scenes of Immunotherapy Failure

“…The scientific rationale for the use of HDAC inhibitors (HDACi) or DNA methyltransferase inhibitors (DNMTi) in ongoing clinical trials in cancer patients relies on the ability of these drugs to inhibit tumor cell growth and to induce cell differentiation [107]. However, DNMTi and HDACi are also capable of upregulating the expression of TAAs in different solid tumors [108][109][110][111], thus potentially sensitizing cancer cells to ICIs by upregulating CTLA4, PD-1, PD-L1, and PD- Taken together, published data indicate that bulk tumor cells and CSCs may exploit epigenetic repression of specific immune genes to escape killing by immune cells. It is likely that the interplay between genetic and epigenetic modifications affects the carcinogenesis process and takes part in the selective pressures involved in immune cell escape.…”

“…The scientific rationale for the use of HDAC inhibitors (HDACi) or DNA methyltransferase inhibitors (DNMTi) in ongoing clinical trials in cancer patients relies on the ability of of 15 these drugs to inhibit tumor cell growth and to induce cell differentiation [107]. However, DNMTi and HDACi are also capable of upregulating the expression of TAAs in different solid tumors [108][109][110][111], thus potentially sensitizing cancer cells to ICIs by upregulating CTLA4, PD-1, PD-L1, and PD-L2 molecules on both tumor cells and TILs [112,113]. HDACi can also restore the expression of MHC class I and II molecules, which are downregulated as a result of transcriptional alterations in the IFNγ and NF-kB (for MHC class I) or the CIITA (for MHC class II) pathways [108], thus facilitating innate and adaptive antitumor immune responses.…”