GZ17-6.02 interacts with proteasome inhibitors to kill multiple myeloma cells.

GZ17-6.02, a synthetically manufactured compound containing isovanillin, harmine and curcumin, has undergone phase I evaluation in patients with solid tumors (NCT03775525) with a recommended phase 2 dose (RP2D) of 375 mg PO BID. GZ17-6.02 was more efficacious as a single agent at killing multiple myeloma cells than had previously been observed in solid tumor cell types. GZ17-6.02 interacted with proteasome inhibitors in a greater than additive fashion to kill myeloma cells and alone it killed inhibitor-resistant cells to a similar extent. The drug combination of GZ17-6.02 and bortezomib activated ATM, the AMPK and PERK and inactivated ULK1, mTORC1, eIF2α, NFκB and the Hippo pathway. The combination increased ATG13 S318 phosphorylation and the expression of Beclin1, ATG5, BAK and BIM, and reduced the levels of BCL-XL and MCL1. GZ17-6.02 interacted with bortezomib to enhance autophagosome formation and autophagic flux, and knock down of ATM, AMPKα, ULK1, Beclin1 or ATG5 significantly reduced both autophagy and tumor cell killing. Knock down of BAK and BIM significantly reduced tumor cell killing. The expression of HDACs1/2/3 was significantly reduced beyond that previously observed in solid tumor cells and required autophagy. This was associated with increased acetylation and methylation of histone H3. Combined knock down of HDACs1/2/3 caused activation of ATM and the AMPK and caused inactivation of ULK1, mTORC1, NFκB and the Hippo pathway. HDAC knock down also enhanced ATG13 phosphorylation, increased BAK levels and reduced those of BCL-XL. Collectively, our present studies support performing additional in vivo studies with multiple myeloma cells.

A phase 1 study of regorafenib and sildenafil in adults with advanced solid tumors.

The purpose of this study is to establish the recommended phase 2 dose for regorafenib in combination with sildenafil for patients with advanced solid tumors. Secondary outcomes included identification of antitumor effects of regorafenib and sildenafil, toxicity of the combination, determination of PDE5 expression in tumor samples, and the impact of sildenafil on the pharmacokinetics of regorafenib. This study was a phase 1, open-label single-arm dose-escalation trial using a 3 + 3 design. Additional patients were enrolled at the maximum tolerated dose (MTD) until a total of 12 patients were treated at the MTD. A total of 29 patients were treated in this study. The median duration of treatment was 8 weeks. The recommended phase 2 doses determined in this study are regorafenib 160 mg daily with sildenafil 100 mg daily. The most common toxicities included palmar-plantar erythrodysesthesia syndrome (20 patients, 69%) and hypophosphatemia (18 patients, 62%). Two patients (7%) experienced grade 4 lipase increase. Objective responses were not observed; however, 14 patients (48%) had a period of stable disease during the study. Stable disease for up to 12 months was observed in patients with ovarian cancer as well as up to 20 months for a patient with cervical cancer. The combination of regorafenib and sildenafil at the recommended phase 2 dose is safe and generally well tolerated. Disease control in patients with gynecologic malignancies was especially encouraging. Further evaluation of the combination of regorafenib and sildenafil in gynecologic malignancies is warranted. Clinical Trial Registration Number: NCT02466802.

GZ17-6.02 interacts with bexarotene to kill mycosis fungoides cells.

GZ17-6.02, composed of curcumin, harmine and isovanillin, has undergone phase I evaluation in patients with solid tumors (NCT03775525) with an RP2D of 375 mg PO BID. The biology of GZ17-6.02 in malignant T cells and in particular those derived from mycosis fungoides (MF) patients, has not been studied. GZ17-6.02 alone and in combination with standard-of-care agents was effective in killing MF cells. All three components are necessary for optimal killing of MF cells. GZ17-6.02 activated ATM, the AMPK, NFκB and PERK and inactivated ERK1/2, AKT, ULK1, mTORC1, eIF2α, and reduced the expression of BCL-XL and MCL1. GZ17-6.02 increased ATG13 S318 phosphorylation and the expression of Beclin1, ATG5, BAK and BIM. GZ17-6.02 in a dose-dependent fashion enhanced autophagosome formation and autophagic flux, and tumor cell killing. Signaling by ATM and AMPK were both required for efficient killing but not for the dose-response effect whereas ER stress (eIF2α) and macroautophagy (Beclin1, ATG5) were required for both efficient killing and the dose-response. Knock down of the death receptor CD95 reduced killing by ~20% and interacted with autophagy inhibition to further reduce killing, collectively, by ~70%. Inhibition of autophagy and knock down of death-mediators downstream of the mitochondrion, AIF and caspase 3, almost abolished tumor cell killing. Hence in MF cells, GZ17-6.02 is a multi-factorial killer, utilizing ER stress, macroautophagy, death receptor signaling and directly causing mitochondrial dysfunction.

Autophagy as a therapeutic mechanism to kill drug-resistant cancer cells.

Herein we discuss multiple pre-clinical projects developed by our group that have been translated into patients at Massey Cancer Center. Our work has used multi-kinase inhibitors, for example, sorafenib, regorafenib and neratinib, and combined with additional agents, for example, histone deacetylase inhibitors, the thymidylate synthase inhibitor pemetrexed, and PDE5 inhibitors. In broad-brush terms, our experience has been that these drug combinations enhance signaling by ATM-AMPK-ULK-1 and decrease signaling from growth factor receptors and RAS proteins, thereby lowering the activities of the intracellular signaling kinase ERK1/2, AKT, mTOR and p70 S6K . This collectively results in reduced protein synthesis and the induction of an endoplasmic reticulum stress response alongside autophagosome formation and autophagic flux. The rupture of autolysosomes, releasing proteases such as cathepsin B into the cytosol results in the cleavage and activation of the toxic BH3 domain protein BID which cooperates with BAX, BAK and BIM to cause mitochondrial dysfunction, leading to the release of cytochrome c and AIF, which then execute the tumor cell. For each of our two-drug combinations, we then performed additional laboratory-based studies to define the development of evolutionary resistance mechanisms, with the long-term concept of performing new three-drug clinical trials to prolong therapeutic efficacy and disease control.

Cellular responses after (neratinib plus pemetrexed) exposure in NSCLC cells.

We previously demonstrated that neratinib interacted with pemetrexed to kill non-small cell lung cancer (NSCLC) cells. From developing other drug combinations, we observed that several days following exposure, cells activated survival mechanisms to counteract drug toxicity. The present studies attempted to define mechanisms that evolve to reduce the efficacy of neratinib and pemetrexed. Neratinib and pemetrexed synergized to kill NSCLC cells expressing wild-type RAS proteins, mutant KRAS (G12S; Q61H; G12A and G12C) or mutant NRAS (Q61K) or mutant ERBB1 (L858R; L858R T790M and exon 19 deletion). Neratinib and pemetrexed interacted in a greater than additive fashion to kill after 24 h, and after a further 24 h culture in the absence of drugs. Mutant KRAS G12V was more cytoprotective than either activated MEK1 or activated AKT. Knockdown of mutant KRAS reduced drug combination killing at the 48 h timepoint. Despite culture for 24 h in the absence of the drugs, the expression and activities of ERBB1, ERBB2 and ERBB4 remained significantly lower as did the activities of mammalian target of rapamycin (mTOR) C1 and mTORC2. The drug combination reduced KRAS and NRAS levels for 24 h, however, in the absence of the drugs, RAS levels had normalized by 48 h. Expression of Beclin1 and ATG5 remained elevated and of MCL1 and BCL-XL lower. No evolutionary activations of survival signaling by ERBB3, c-KIT, c-MET or PDGFRß or in intracellular signaling pathways were observed. These findings argue against the development of 'early' resistance mechanisms after neratinib and pemetrexed exposure. Future studies will be required to understand how NSCLC cells become resistant to neratinib and pemetrexed.

The epigenetic regulation of cancer cell recovery from therapy exposure and its implications as a novel therapeutic strategy for preventing disease recurrence.

The ultimate goal of cancer therapy is the elimination of disease from patients. Most directly, this occurs through therapy-induced cell death. Therapy-induced growth arrest can also be a desirable outcome, if prolonged. Unfortunately, therapy-induced growth arrest is rarely durable and the recovering cell population can contribute to cancer recurrence. Consequently, therapeutic strategies that eliminate residual cancer cells reduce opportunities for recurrence. Recovery can occur through diverse mechanisms including quiescence or diapause, exit from senescence, suppression of apoptosis, cytoprotective autophagy, and reductive divisions resulting from polyploidy. Epigenetic regulation of the genome represents a fundamental regulatory mechanism integral to cancer-specific biology, including the recovery from therapy. Epigenetic pathways are particularly attractive therapeutic targets because they are reversible, without changes in DNA, and are catalyzed by druggable enzymes. Previous use of epigenetic-targeting therapies in combination with cancer therapeutics has not been widely successful because of either unacceptable toxicity or limited efficacy. The use of epigenetic-targeting therapies after a significant interval following initial cancer therapy could potentially reduce the toxicity of combination strategies, and possibly exploit essential epigenetic states following therapy exposure. This review examines the feasibility of targeting epigenetic mechanisms using a sequential approach to eliminate residual therapy-arrested populations, that might possibly prevent recovery and disease recurrence.

A novel combination of isovanillin, curcumin, and harmine (GZ17-6.02) enhances cell death and alters signaling in actinic keratoses cells when compared to individual components and two-component combinations.

Actinic keratosis is a pre-malignant skin disease caused by excessive exposure to ultraviolet light. The present studies further defined the biology of a novel combination of isovanillin, curcumin, and harmine in actinic keratosis cells in vitro . An oral formulation (GZ17-6.02) and topical preparation (GZ21T) comprised of the same fixed, stoichiometric ratio have been developed. Together, the three active ingredients killed actinic keratosis cells more effectively than any of its component parts as either individual agents or when combined in pairs. The three active ingredients caused greater levels of DNA damage than any of its component parts as either individual agents or when combined in pairs. As a single agent, compared to isolated components, GZ17-6.02/GZ21T caused significantly greater activation of PKR-like endoplasmic reticulum kinase, the AMP-dependent protein kinase, and ULK1 and significantly reduced the activities of mTORC1, AKT, and YAP. Knockdown of the autophagy-regulatory proteins ULK1, Beclin1, or ATG5 significantly reduced the lethality of GZ17-6.02/GZ21T alone. Expression of an activated mammalian target of rapamycin mutant suppressed autophagosome formation and autophagic flux and reduced tumor cell killing. Blockade of both autophagy and death receptor signaling abolished drug-induced actinic keratosis cell death. Our data demonstrate that the unique combination of isovanillin, curcumin, and harmine represents a novel therapeutic with the potential to treat actinic keratosis in a manner different from the individual components or pairs of the components.

GZ17-6.02 kills prostate cancer cells in vitro and in vivo.

GZ17-6.02 is undergoing clinical evaluation in solid tumors and lymphoma. We defined the biology of GZ17-6.02 in prostate cancer cells and determined whether it interacted with the PARP1 inhibitor olaparib to enhance tumor cell killing. GZ17-6.02 interacted in a greater than additive fashion with olaparib to kill prostate cancer cells, regardless of androgen receptor expression or loss of PTEN function. Mechanistically, GZ17-6.02 initially caused peri-nuclear activation of ataxia-telangiectasia mutated (ATM) that was followed after several hours by activation of nuclear ATM, and which at this time point was associated with increased levels of DNA damage. Directly downstream of ATM, GZ17-6.02 and olaparib cooperated to activate the AMP-dependent protein kinase (AMPK) which then activated the kinase ULK1, resulting in autophagosome formation that was followed by autophagic flux. Knock down of ATM, AMPKα or the autophagy-regulatory proteins Beclin1 or ATG5 significantly reduced tumor cell killing. GZ17-6.02 and olaparib cooperated to activate protein kinase R which phosphorylated and inactivated eIF2α, i.e., enhanced endoplasmic reticulum (ER) stress signaling. Knock down of eIF2α also significantly reduced autophagosome formation and tumor cell killing. We conclude that GZ17-6.02 and olaparib interact to kill prostate cancer cells in vitro by increasing autophagy and by enhancing ER stress signaling. In vivo, GZ17-6.02 as a single agent profoundly reduced tumor growth and significantly prolonged animal survival. GZ17-6.02 interacted with olaparib to further suppress the growth of LNCaP tumors without ultimately enhancing animal survival. Our data support the consideration of GZ17-6.02 as a possible therapeutic agent in patients with AR+ prostate cancer.

AR12 increases BAG3 expression which is essential for Tau and APP degradation via LC3-associated phagocytosis and macroautophagy.

We defined the mechanisms by which the chaperone ATPase inhibitor AR12 and the multi-kinase inhibitor neratinib interacted to reduce expression of Tau and amyloid-precursor protein (APP) in microglia and neuronal cells. AR12 and neratinib interacted to increase the phosphorylation of eIF2A S51 and the expression of BAG3, Beclin1 and ATG5, and in parallel, enhanced autophagosome formation and autophagic flux. Knock down of BAG3, Beclin1 or ATG5 abolished autophagosome formation and significantly reduced degradation of p62, LAMP2, Tau, APP, and GRP78 (total and plasma membrane). Knock down of Rubicon, a key component of LC3-associated phagocytosis (LAP), significantly reduced autophagosome formation but not autophagic flux and prevented degradation of Tau, APP, and cell surface GRP78, but not ER-localized GRP78. Knock down of Beclin1, ATG5 or Rubicon or over-expression of GRP78 prevented the significant increase in eIF2A phosphorylation. Knock down of eIF2A prevented the increase in BAG3 expression and significantly reduced autophagosome formation, autophagic flux, and it prevented Tau and APP degradation. We conclude that AR12 has the potential to reduce Tau and APP levels in neurons and microglia via the actions of LAP, endoplasmic reticulum stress signaling and macroautophagy. We hypothesize that the initial inactivation of GRP78 catalytic function by AR12 facilitates an initial increase in eIF2A phosphorylation which in turn is essential for greater levels of eIF2A phosphorylation, greater levels of BAG3 and macroautophagy and eventually leading to significant amounts of APP/Tau degradation.

Mechanisms of GZ17-6.02 resistance.

OBJECTIVES: The drug GZ17-6.02 is undergoing phase I in solid tumor patients (NCT03775525). The present studies initially determined the impact of prolonged exposure of colorectal tumors to GZ17-6.02, and to determine whether GZ17-6.02 enhanced the efficacy of an anti-PD1 antibody. Subsequently, studies defined the evolutionary resistance mechanisms in tumor cells previously exposed to GZ17-6.02. METHODS: IACUC-approved animal studies were performed. In cell immunoblotting, cell transfections and trypan blue death assays were performed. RESULTS: Prolonged exposure of colorectal tumors to GZ17-6.02 enhanced the efficacy of 5-fluorouracil and of an anti-PD1 antibody, significantly prolonging animal survival. Tumor cells previously exposed to GZ17-6.02 in vivo had elevated their expression of ERBB2 and ERBB3, and increased phosphorylation of ERBB1, ERBB3, PDGFRß, AKT T308, ERK1/2, p70 S6K T389, STAT5 Y694 and c-SRC Y416. The phosphorylation of c-SRC Y527 declined. The efficacy of ERBB receptor inhibitors at killing these resistant tumor cells was unaltered by prior GZ17-6.02 exposure whereas the efficacy of multi-kinase/PDGFRß inhibitors was significantly reduced. Treatment of colon cancer cells with GZ17-6.02 rapidly reduced the levels of multiple HDAC proteins and altered their subcellular localization. Isolates from resistant tumors expressed less CD95 and FAS-L. HDAC inhibitors enhanced CD95 and FAS-L levels in the resistant cells via activation of NFκB and HDAC inhibitors restored the efficacy of GZ17-6.02 to near control levels. CONCLUSIONS: Our findings demonstrate that GZ17-6.02 has the potential to be developed as a colon cancer therapeutic and that resistance to the drug can be partially reversed by HDAC inhibitors.

GZ17-6.02 and axitinib interact to kill renal carcinoma cells.

GZ17-6.02 is undergoing clinical evaluation in solid tumors and lymphoma. The present studies were performed to define its biology in renal carcinoma cells and to determine whether it interacted with axitinib to enhance tumor cell killing. GZ17-6.02 interacted in an arithmetically greater than additive fashion with axitinib to kill kidney cancer cells. GZ17-6.02 and axitinib cooperated to inactivate ERBB2, c-MET, c-KIT, c-SRC, the AMPK, STAT3, STAT5 and eIF2α and to activate PERK, ULK1 and ATG13. The drugs interacted to increase the expression of FAS-L and to decrease the levels of MCL1, BCL-XL, and HDACs 1-3. The drugs as single agents inactivated the Hippo pathway. GZ17-6.02 and axitinib interacted to enhance autophagosome formation and autophagic flux. Knock down of Beclin1, ATG5, eIF2α, toxic BH3 domain proteins or CD95/FADD significantly reduced drug combination lethality. GZ17-6.02 and axitinib increased the expression of BAK, BIM, Beclin1 and ATG5, effects blocked by knock down of eIF2α. The drugs increased phosphorylation of ULK1 S757 and ATG13 S318 and decreased the phosphorylation of mTORC1 and mTORC2, effects blocked by knock down of AMPKα. Knock down of Beclin1 or ATG5 prevented the drug combination reducing expression of HDACs 1-3 and from enhancing the expression of MHCA. Knock down of HDACs 1-3 enhanced MHCA expression. We conclude that GZ17-6.02 and axitinib interact to kill requiring ER stress signaling, autophagy and death receptor signaling. Autophagic degradation of HDACs played a key role in enhancing MHCA expression and of a potential improved response to checkpoint inhibitory immunotherapy.

GZ17-6.02 and palbociclib interact to kill ER+ breast cancer cells.

GZ17-6.02 is presently undergoing clinical evaluation in solid tumors and lymphoma. The present studies were performed to define its biology in estrogen receptor positive breast cancer cells and to determine whether it interacted with palbociclib to enhance tumor cell killing. GZ17-6.02 interacted in an additive fashion with palbociclib to kill ER+ breast cancer cells. GZ17-6.02 and palbociclib cooperated to inactivate mTOR and AKT and to activate ULK1 and PERK. The drugs interacted to increase the expression of FAS-L and BAX, and to decrease the levels of MCL1, the estrogen receptor, and HDACs 1-3. Palbociclib activated ERBB3, an effect blocked by GZ17-6.02. GZ17-6.02 and palbociclib interacted to increase the expression of multiple toxic BH3 domain proteins and to reduce MCL1 and BCL-XL expression. Knock down of FAS-L reduced the lethality of [GZ17-6.02 + palbociclib]. GZ17-6.02 and palbociclib interacted to enhance autophagosome formation and autophagic flux. Knock down of Beclin1, ATG5, BAG3, eIF2α, toxic BH3 domain proteins or CD95 significantly reduced drug combination lethality. GZ17-6.02 and palbociclib increased the expression of Beclin1 and ATG5, effects blocked by knock down of eIF2α. The drugs also increased the phosphorylation of the AMPK and ATG13, effects blocked by knock down of ATM. Knock down of ATM or the AMPK, or expression of activated mTOR significantly reduced the abilities of GZ17-6.02 and palbociclib to enhance autophagosome formation and autophagic flux.

Neratinib kills B-RAF V600E melanoma via ROS-dependent autophagosome formation and death receptor signaling.

Melanoma cells expressing mutant B-RAF V600E are susceptible to treatment with the combination of a B-RAF inhibitor and a MEK1/2 inhibitor. We investigated the impact of the ERBB family and MAP4K inhibitor neratinib on the biology of PDX isolates of cutaneous melanoma expressing B-RAF V600E. Neratinib synergized with HDAC inhibitors to kill melanoma cells at their physiologic concentrations. Neratinib activated ATM, AMPK, ULK1, and PERK and inactivated mTORC1/2, ERK1/2, eIF2 alpha, and STAT3. Neratinib increased expression of Beclin1, ATG5, CD95, and FAS-L and decreased levels of multiple toxic BH3 domain proteins, MCL1, BCL-XL, FLIP-s, and ERBB1/2/4. ATG13 S318 phosphorylation and autophagosome formation was dependent upon ATM, and activation of ATM was dependent on reactive oxygen species. Reduced expression of ERBB1/2/4 required autophagosome formation and reduced MCL1/BCL-XL levels required eIF2 alpha phosphorylation. Maximal levels of eIF2 alpha phosphorylation required signaling by ATM-AMPK and autophagosome formation. Knock down of eIF2 alpha, CD95, FAS-L, Beclin1, and ATG5 or over-expression of FLIP-s significantly reduced killing. Combined knock down of Beclin1 and CD95 abolished cell death. Our data demonstrate that PDX melanoma cells expressing B-RAF V600E are susceptible to being killed by neratinib and more so when combined with HDACi.

Axitinib and HDAC Inhibitors Interact to Kill Sarcoma Cells.

We have extended our analyses of HDAC inhibitor biology in sarcoma. The multi-kinase inhibitor axitinib interacted with multiple HDAC inhibitors to kill sarcoma cells. Axitinib and HDAC inhibitors interacted in a greater than additive fashion to inactivate AKT, mTORC1 and mTORC2, and to increase Raptor S722/S792 phosphorylation. Individually, all drugs increased phosphorylation of ATM S1981, AMPKα T172, ULK1 S317 and ATG13 S318 and reduced ULK1 S757 phosphorylation; this correlated with enhanced autophagic flux. Increased phosphorylation of ULK1 S317 and of Raptor S722/S792 required ATM-AMPK signaling. ULK1 S757 is a recognized site for mTORC1 and knock down of either ATM or AMPKα reduced the drug-induced dephosphorylation of this site. Combined exposure of cells to axitinib and an HDAC inhibitor significantly reduced the expression of HDAC1, HDAC2, HDAC3, HDAC4, HDAC6 and HDAC7. No response was observed for HDACs 10 and 11. Knock down of ULK1, Beclin1 or ATG5 prevented the decline in HDAC expression, as did expression of a constitutively active mTOR protein. Axitinib combined with HDAC inhibitors enhanced expression of Class I MHCA and reduced expression of PD-L1 which was recapitulated via knock down studies, particularly of HDACs 1 and 3. In vivo, axitinib and the HDAC inhibitor entinostat interacted to significantly reduce tumor growth. Collectively our findings support the exploration of axitinib and HDAC inhibitors being developed as a novel sarcoma therapy.

GZ17-6.02 and Pemetrexed Interact to Kill Osimertinib-Resistant NSCLC Cells That Express Mutant ERBB1 Proteins.

We determined the molecular mechanisms by which the novel therapeutic GZ17-6.02 killed non-small cell lung cancer (NSCLC) cells. Erlotinib, afatinib, and osimertinib interacted with GZ17-6.02 to kill NSCLC cells expressing mutant EGFR proteins. GZ17-6.02 did not interact with any EGFR inhibitor to kill osimertinib-resistant cells. GZ17-6.02 interacted with the thymidylate synthase inhibitor pemetrexed to kill NSCLC cells expressing mutant ERBB1 proteins or mutant RAS proteins or cells that were resistant to EGFR inhibitors. The drugs interacted to activate ATM, the AMPK, and ULK1 and inactivate mTORC1, mTORC2, ERK1/2, AKT, eIF2α; and c-SRC. Knockdown of ATM or AMPKα1 prevented ULK1 activation. The drugs interacted to cause autophagosome formation followed by flux, which was significantly reduced by knockdown of ATM, AMPKα1, and eIF2α, or by expression of an activated mTOR protein. Knockdown of Beclin1, ATG5, or [BAX + BAK] partially though significantly reduced drug combination lethality as did expression of activated mTOR/AKT/MEK1 or over-expression of BCL-XL. Expression of dominant negative caspase 9 weakly reduced killing. The drug combination reduced the expression of HDAC2 and HDAC3, which correlated with lower PD-L1, IDO1, and ODC levels and increased MHCA expression. Collectively, our data support consideration of combining GZ17-6.02 and pemetrexed in osimertinib-resistant NSCLC.

The development of multi-kinase inhibitors as pancreatic cancer therapeutics.

Pancreatic cancer is an almost incurable malignancy whose incidence has increased over the past 30 years. Instead of pursuing the development of modalities utilizing 'traditional' cytotoxic chemotherapeutic agents, we have explored the possibilities of developing novel multi-kinase inhibitor drug combinations to kill this tumor type. Several approaches using the multi-kinase inhibitors sorafenib, regorafenib, and neratinib have been safely translated from the bench to the bedside, with objective anti-tumor responses. This review will discuss our prior preclinical and clinical studies and discuss future clinical opportunities in this disease.

Inhibition of heat shock proteins increases autophagosome formation, and reduces the expression of APP, Tau, SOD1 G93A and TDP-43.

Aberrant expression and denaturation of Tau, amyloid-beta and TDP-43 can lead to cell death and is a major component of pathologies such as Alzheimer's Disease (AD). AD neurons exhibit a reduced ability to form autophagosomes and degrade proteins via autophagy. Using genetically manipulated colon cancer cells we determined whether drugs that directly inhibit the chaperone ATPase activity or cause chaperone degradation and endoplasmic reticulum stress signaling leading to macroautophagy could reduce the levels of these proteins. The antiviral chaperone ATPase inhibitor AR12 reduced the ATPase activities and total expression of GRP78, HSP90, and HSP70, and of Tau, Tau 301L, APP, APP692, APP715, SOD1 G93A and TDP-43. In parallel, it increased the phosphorylation of ATG13 S318 and eIF2A S51 and caused eIF2A-dependent autophagosome formation and autophagic flux. Knock down of Beclin1 or ATG5 prevented chaperone, APP and Tau degradation. Neratinib, used to treat HER2+ breast cancer, reduced chaperone levels and expression of Tau and APP via macroautophagy, and neratinib interacted with AR12 to cause further reductions in protein levels. The autophagy-regulatory protein ATG16L1 is expressed as two isoforms, T300 or A300: Africans trend to express T300 and Europeans A300. We observed higher basal expression of Tau in T300 cells when compared to isogenic A300 cells. ATG16L1 isoform expression did not alter basal levels of HSP90, HSP70 or HSP27, however, basal levels of GRP78 were reduced in A300 cells. The abilities of both AR12 and neratinib to stimulate ATG13 S318 and eIF2A S51 phosphorylation and autophagic flux was also reduced in A300 cells. Our data support further evaluation of AR12 and neratinib in neuronal cells as repurposed treatments for AD.

Osimertinib-resistant NSCLC cells activate ERBB2 and YAP/TAZ and are killed by neratinib.

We performed additional mechanistic analyses to redefine neratinib biology and determined the mechanisms by which the multi-kinase inhibitor neratinib interacted with the thymidylate synthase inhibitor pemetrexed to kill NSCLC cells expressing either mutant KRAS (G12S; Q61H; G12A; G12C) or mutant NRAS (Q61K) or mutant ERBB1 (L858R; L858R T790M; exon 19 deletion). Neratinib rapidly reduced KRASG12V and RAC1G12V nanoclustering which was followed by KRASG12V, but not RAC1G12V, being extensively mislocalized away from the plasma membrane. This correlated with reduced levels of, and reorganized membrane localization of phosphatidylserine and cholesterol. Reduced nanoclustering was not associated with inactivation of ERBB1, Merlin or Ezrin. The drug combination killed cells expressing mutant KRAS, NRAS or mutant ERBB1 proteins. Afatinib or osimertinib resistant cells were killed with a similar efficacy to non-resistant cells. Compared to osimertinib-resistant cells, sensitive cells had less ERBB2 Y1248 phosphorylation. In osimertinib resistant H1975 cells, the drug combination was less capable of inactivating AKT, mTOR, STAT3, STAT5, ERK1/2 whereas it gained the ability to inactivate ERBB3. In resistant H1650 cells, the drug combination was less capable of inactivating JAK2 and STAT5. Sensitive cells exhibited elevated basal phosphorylation of YAP and TAZ. In resistant cells, portions of YAP and TAZ were localized in the nucleus. [Neratinib + pemetrexed] increased phosphorylation of YAP and TAZ, caused their nuclear exit, and enhanced ERBB2 degradation. Thus, neratinib targets an unidentified protein whose functional inhibition directly results in RAS inactivation and tumor cell killing. Our data prove that, albeit indirectly, oncogenic RAS proteins are druggable by neratinib.