GZ17‐6.02 initiates DNA damage causing autophagosome‐dependent HDAC degradation resulting in enhanced anti‐PD1 checkpoint inhibitory antibody efficacy

Abstract

Our studies examined the molecular mechanisms by which the novel cancer therapeutic GZ17‐6.02 (NCT03775525) killed GI tumor cells. TZ17‐6.02 activated ATM which was responsible for increased phosphorylation of nuclear γH2AX and AMPKα T172. ATM‐AMPK signaling was responsible for the subsequent inactivation of mTORC1 and mTORC2, dephosphorylation of ULK1 S757, and increased phosphorylation of ULK1 S317 and of ATG13 S318, which collectively caused enhanced autophagosome formation. GZ17‐6.02 interacted with 5‐fluorouracil in an additive to greater than additive fashion to kill all of the tested GI tumor cell types. This was associated with greater ATM activation and a greater mammalian target of rapamycin inactivation and autophagosome induction. As a result, autophagy‐dependent degradation of multiple histone deacetylase (HDAC) proteins and chaperone proteins occurred. Loss of HDAC expression was causal in reduced expression of programed death ligand 1 (PD‐L1), ornithine decarboxylase, and indole amine 2,3‐dioxygenase (IDO1) and in the elevated expression of major histocompatibility complex Class IA (MHCA). Treatment with GZ17‐6.02 also resulted in enhanced efficacy of a subsequently administered anti‐PD1 checkpoint inhibitory antibody. Thus, the primary mode of GZ17‐6.02 action is to induce a DNA damage response concomitant with ATM activation, that triggers a series of interconnected molecular events that result in tumor cell death and enhanced immunogenicity.

GZ17-6.02 and Doxorubicin Interact to Kill Sarcoma Cells via Autophagy and Death Receptor Signaling

“…Our cell signaling data with 602 and doxorubicin in sarcoma cells was similar, though not identical, to our prior work with 602 in GI tumor cells ( 2 ). Knock down of ATM prevented the drug combination from activating the AMPK and ULK1, inactivating mTORC1 or increasing ATG13 S318 phosphorylation ( Supplementary Figure 9 ).…”

“…Our preliminary studies demonstrated that GZ17-6.02 (602) interacted with doxorubicin to kill HT1080 cells ( Figure 1A ). Exposure of MES cells to 602 alone caused a similar amount of tumor cell death when compared to prior studies in GI tumor cells, whereas HT1080 cells appeared to be more sensitive ( 2 ). In colony formation assays 602 and doxorubicin synergized to kill sarcoma cells with combination index values below ~1.0 ( Figure 1B ).…”

“…The present studies were performed to determine the biology of sarcoma cells when exposed to GZ17-6.02. GZ17-6.02 as a single agent caused tumor cell death to a similar degree as was previously noted in GI tumor cells, and when 602 was combined with a former standard of care agent for the treatment of sarcoma, doxorubicin, additional cell killing was observed ( 2 ).…”

“…GZ17-6.02 (602) comprises of three natural products, curcumin, isovanillin, and harmine ( 1 , 2 ). In our most recent studies in eight gastrointestinal tumor cell lines we determined that low concentrations of 602 killed tumor cells and interacted with a standard of care drug for these tumor types, 5-fluorouracil (5FU), to further enhance tumor cell death ( 2 ). GZ17-6.02 activated an ATM-AMPK signaling module which was responsible for inactivation of mTORC1 and mTORC2, dephosphorylation of ULK1 S757, and increased phosphorylation of ULK1 S317 and of ATG13 S318.…”

GZ17-6.02 Interacts With [MEK1/2 and B-RAF Inhibitors] to Kill Melanoma Cells

“…The novel cancer therapeutic GZ17-6.02 undergoing phase I evaluation in solid tumor patients. GZ17-6.02 is comprised of three natural chemicals; curcumin (10%); isovanillin (77%); and harmine (13%) (10)(11)(12). The most widely studied of these three compounds is curcumin; turmeric, the spice most associated with Indian cuisine is comprised~95% of curcumin and curcuminoid derivatives.…”