Acidic ascites inhibits gastric and ovarian cancer cell proliferation and correlate with the metabolomic, lipidomic, and inflammatory phenotype of human patients

Abstract

Background Gastric and ovarian cancer are two of the most common cancer worldwide, and peritoneal metastasis occurs in the advanced stage of those two cancers. The adverse prognosis patients with peritoneal carcinoma from gastric and ovarian cancers is closely tied to peritoneal metastasis and the development of malignant ascites. Nevertheless, the precise mechanisms through which ascites in the peritoneal cavity impact tumor metabolism and recurrence remain elusive. This study takes an exploratory approach, seeking to comprehensively analyze the molecular and physicochemical traits of malignant ascites triggered by gastric and ovarian cancers, and to examine their impacts on the in vitro proliferation of gastric and ovarian cancer cells.

Methods We investigated how ascites affect cancer cells by measuring intraperitoneal pH and physical-chemical parameters distribution in cancer and benign control patients. MKN45 and OAW42 cell lines were cultured under different pH conditions, with subsequent assessment of tumor cell metabolic activity, adhesion, anti-apoptotic potential, and migratory capabilities via MTT assay, adhesion assay, flow cytometry, and scratch assay. Additionally, a three-dimensional spherical model was employed to examine the characteristics of gastric and ovarian cancer cells at different pH levels using scanning electron microscopy. Furthermore, 10% corresponding malignant ascites were introduced to MKN45 and OAW42 cell lines to evaluate their impact on tumor proliferation. Finally, a comprehensive phenotypic analysis of ovarian ascites samples was conducted, incorporating 1H-NMR-based metabolomics, blood gas analyzer-based analysis, and flow cytometry with a 13-complex cytokine panel.

Results Ascites pH was higher in cancer patients (7.60±0.38) than in control (6.99±0.19) and even more so in stage IV (7.69±0.20) than in stage III (7.45±0.27). Ovarian and gastric cancer cells within 3D spherical structures exhibit rapid proliferation in a slightly alkaline environment. Tumor characteristics, including metabolic activity, adhesion, resistance to apoptosis, and migratory ability, are susceptible to inhibition through pH reduction in the cell culture medium. However, malignant ascites demonstrate resilience against tumor cells exposed to acidic pH conditions. Metabolomics analysis of malignant ascites from ovarian cancer patients revealed notably higher concentrations of alanine, isoleucine, phenylalanine, and glutamine in stage IV ovarian cancer patients compared to those in stages II-III. In comparison, concentrations of 3-hydroxybutyrate were notably higher in the ascites of patients with ovarian cancer at lower stages. Increased ascites pH was positively correlated with lipid metabolites. IL-8 displayed a positive correlation with lipid metabolites and acetate, while glutathione and carnitine exhibited a negative correlation with cytokines IL-6 and chemokines IL-8 and MCP-1.

Conclusion Malignant ascites play a role in advancing ovarian and gastric cancers, potentially linked to their alkaline nature. Furthermore, variances in metabolites and cytokines within ascites from advanced-stage patients could offer refined stratification for ovarian cancer patients. These discoveries deepen our comprehension of ovarian cancer ascites pathology. Controlling pH levels may prove to be an effective strategy in preventing and treating peritoneal metastases.