Similarities and Differences of Hsp70, hsc70, Grp78 and Mortalin as Cancer Biomarkers and Drug Targets

Background: Upregulation of Heath Shock Protein 70 (HSP70) chaperones supports cancer cell survival. Their high homology causes a challenge to differentiate them in experimental or prevention and treatment strategies. The objective of this investigation was to determine similarities and differences of Hsp70, hsc70, Grp78 and Mortalin members of the HSP70 family encoded by HSPA1, HSPA8, HSPA5 and HSPA9 genes, respectively. Methods: Literature reviews were conducted using HSPA1, HSPA5, HSPA8 and HSPA9 gene or protein names or synonyms combined with biological or cancer-relevant terms. Ingenuity Pathway Analysis was used to identify and compare profiles of proteins that directly bind individual chaperones and their associated pathways. TCGA data was probed to identify associations of hsc70 with cancer patient survival. ClinicalTrials.gov was used to identify HSP70 family studies. Results: The chaperones have similar protein folding functions. Their different cellular effects are determined by co-chaperones and client proteins combined with their intra- and extra-cellular localizations. Their upregulation is associated with worse patient prognosis in multiple cancers and can stimulate tumor immune responses or drug resistance. Their inhibition selectively kills cancer over healthy cells. Conclusions: Differences in Hsp70, hsc70, Grp78 and mortalin provide opportunities to calibrate HSP70 inhibitors for individual cancers and combination therapies.

Potential and mechanism of mebendazole for treatment and maintenance of ovarian cancer

OBJECTIVE

Mebendazole and other anti-parasitic drugs are being used off-prescription based on social media and unofficial accounts of their anti-cancer activity. The purpose of this study was to conduct a controlled evaluation of mebendazole's therapeutic efficacy in cell culture and in vivo models of ovarian cancer. The majority of ovarian cancers harbor p53 null or missense mutations, therefore the effects of p53 mutations and a mutant p53 reactivator, PRIMA-1^MET (APR246) on mebendazole activity were evaluated.

METHODS

Mebendazole was evaluated in cisplatin-resistant high grade serous stage 3C ovarian cancer patient derived xenograft (PDX) models: PDX-0003 (p53 null) and PDX-0030 (p53 positive), and on ovarian cancer cell lines: MES-OV (p53 R282W), ES2 (p53 S241F), A2780 (p53 wild type), SKOV3 parental (p53 null) and isogenic sublines, SKOV3 R273H p53 and SKOV3 R248W p53. Drug synergy and mechanisms were evaluated in cell cultures using isobolograms, clonogenic assays and western blots. Prevention of tumor establishment was studied in a MES-OV orthotopic model.

RESULTS

Mebendazole inhibited growth of ovarian cancer cell cultures at nanomolar concentrations and PDXs at doses up to 50 mg/kg, and reduced orthotopic tumor establishment at 50 mg/kg. The mechanism of mebendazole was associated with p53-independent induction of p21 and tubule depolymerization. PRIMA-1^MET also inhibited tumor establishment and worked synergistically with mebendazole in cell culture to inhibit growth and induce intrinsic apoptosis through a p53- and tubule destabilization-independent mechanism.

CONCLUSION

This work demonstrates the therapeutic potential of repurposing mebendazole and supports clinical development of mebendazole for ovarian cancer therapy and maintenance.

Abstract 2840: Development of a model of dihomo-gamma-linolenic acid interference with platelet promotion of ovarian cancer

Background: Cancer is the second leading cause of deaths worldwide after cardiovascular diseases. A commonality between cancer and cardiovascular diseases is disregulation of platelets. Platelets and cancer are known to promote each other in a feedforward mechanism that is poorly understood. A long chain polyunsaturated fatty acids dihomo-gamma-linolenic acid (DGLA) was shown to reduce cardiovascular events in a platelet dependent manner while the exact mechanism of DGLA-mediated cancer cells death is yet to be explored.

Objectives: The objective of our study was to develop an experimental model to study interventions that could disrupt the cancer/platelets loop.

Methods: The effects of a range of DGLA concentrations on platelet aggregation and growth of high grade serous ovarian cancer cell lines (OVCAR3, MesOV, OVSAHO), normal human fallopian tube secretory epithelial cells (hFTSECs) primary culture and an immortalized hFTSEC cultures were determined with an MTT assay. Cocultures were used to evaluate effects of platelets on ovarian cancer cell line spheroid formation and size and effects of ovarian cancer cells and hFTSECs on platelet aggregation. Results: The minimal cytotoxic DGLA concentrations for cancer and normal epithelial cells were above physiologically-achievable concentrations, and the half maximal inhibitory concentrations (IC50's) were similar across epithelial cell types with the IC50's for hFTSEC primary culture (261 µM) and immortalized culture (206 µM) falling within the range of cancer cell IC50's (153-275 µM). DGLA inhibited platelet aggregation at concentrations ≥250 µM. Platelets increased cancer spheroid sizes in a concentration-dependent manner and cancer cells, but not hFTSECs, induced platelet aggregation in cocultures.

Conclusions: Our model incorporates both platelet effects on cancer cells and cancer cell effects on platelets. Physiologically-achievable DGLA concentrations that affect platelet aggregation without affecting epithelial cells were identified. Minimal doses of DGLA needed to cause cytotoxicity against cancer and normal cells are above levels that are physiologically achievable. Future studies will utilize DGLA doses that can interfere with platelet aggregation without directly causing cytotoxicity to cancer or healthy cells. This experimental model will allow study of DGLA's potential for interfering with platelet promotion of ovarian cancer in the absence of direct effects of DGLA on cancer cells. Funded by NCI R01 CA196200

Citation Format: Zitha Redempta Isingizwe, Doris M. Benbrook. Development of a model of dihomo-gamma-linolenic acid interference with platelet promotion of ovarian cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2840.

Complementary Targeting of Rb Phosphorylation and Growth in Cervical Cancer Cell Cultures and a Xenograft Mouse Model by SHetA2 and Palbociclib

Cervical cancer is caused by high-risk human papillomavirus (HPV) types and treated with conventional chemotherapy with surgery and/or radiation. HPV E6 and E7 proteins increase phosphorylation of retinoblastoma (Rb) by cyclin D1/cyclin dependent kinase (CDK)4/6 complexes. We hypothesized that cyclin D1 degradation by the SHetA2 drug in combination with palbociclib inhibition of CDK4/6 activity synergistically reduces phosphorylated Rb (phospho-Rb) and inhibits cervical cancer growth. The effects of these drugs, alone, and in combination, were evaluated in SiHa and CaSki HPV-positive and C33A HPV-negative cervical cancer cell lines using cell culture, western blots and ELISA, and in a SiHa xenograft model. Endpoints were compared by isobolograms, ANOVA, and Chi-Square. In all cell lines, combination indexes documented synergistic interaction of SHetA2 and palbociclib in association SHetA2 reduction of cyclin D1 and phospho-Rb, palbociclib reduction of phospho-Rb, and enhanced phospho-Rb reduction upon drug combination. Both drugs significantly reduced phospho-Rb and growth of SiHa xenograft tumors as single agents and acted additively when combined, with no evidence of toxicity. Dilated CD31-negative blood vessels adjacent to, or within, areas of necrosis and apoptosis were observed in all drug-treated tumors. These results justify development of the SHetA2 and palbociclib combination for targeting phospho-Rb in cervical cancer treatment.