Citations

Abstract Background Upstream regulators of the homologous recombination (HR) repair pathway are promising targets for overcoming temozolomide (TMZ) resistance. We investigated whether pharmacologic inhibition of Retinoblastoma Binding Protein 4 (RBBP4)/p300-mediated HR activity by CCS1477 or NEO2734 sensitizes glioblastoma (GBM) to TMZ. Methods Lentiviral-mediated shRNA was used to silence RBBP4 and EP300 (p300). A fluorescence-based multiplex flow-cytometric host cell reactivation assay was used to measure DNA repair activity, while TMZ-induced double-strand breaks (DSBs) were assessed using a comet assay and γ-H2AX foci formation. Cytotoxicity was monitored using an Incucyte device, and survival analysis was performed to evaluate efficacy in orthotopic tumor models. Drug distribution was assessed using liquid chromatography-mass spectrometry (LC-MS/MS) and acetylation of lysine 27 of histone H3 (H3K27Ac) immunofluorescence for target inhibition. Promoter occupancy was determined using chromatin immunoprecipitation. Results GBM patient-derived xenograft tumors with high RBBP4 expression showed elevated levels of 6 HR genes (RAD51, RAD50, BRCA1, BARD1, BRIP1, and FIGNL1), with RAD51 and BRIP1 correlating strongly with RBBP4 and p300. Silencing RBBP4 or p300 decreased HR and microhomologous-mediated end joining (MMEJ) activity and delayed repair of TMZ-induced DSBs. CCS1477 and NEO2734 suppressed RAD51 and MYC in a concentration-dependent manner, prolonged γ-H2AX foci, and enhanced TMZ sensitivity. Both compounds inhibited H3K27Ac and were detectable in orthotopic tumors by LC-MS/MS and significantly extended survival alone and in combination with TMZ. Conclusion These findings suggest that the RBBP4/p300-axis is a key regulator of HR-mediated repair of TMZ-induced DSBs, and inhibition by either CCS1477 or NEO2734 may be beneficial as monotherapy, but further studies are needed to determine the benefit of combining these agents with TMZ.

Gastric cancer risk evolves over time due to environmental, dietary, and lifestyle changes, including Helicobacter pylori (H. pylori) infection and consumption of hot peppers (i.e., capsaicin). H. pylori infection promotes gastric mucosal injury in the early phase of capsaicin exposure. This relationship suggests a need to investigate the mechanism of how both H. pylori infection and capsaicin contribute to gastric inflammation and lead to gastric cancer. C57-Balb/c mice were infected with the H. pylori (SS1) strain and then fed capsaicin (0.05% or 0.2 g/kg/day) or not. Consequently, tumor size and phenotype were analyzed to determine the molecular mechanism driving the shift from gastritis to stomach cancer. Moreover, we used 2-difluoromethylornithine (DFMO) in mice to prevent gastric tumorigenesis by reducing inflammation and promoting recovery of disease-free stasis. This study provides evidence showing that a combination of H. pylori infection and capsaicin consumption leads to gastric carcinogenesis mediated through interleukin-6 (IL-6) stimulation with an incidence rate of 50%. The anti-inflammatory role of DFMO highlights the injurious effect of inflammation in gastric cancer development and the need to reduce gastric inflammation for cancer prevention by inhibiting IL-6. Accordingly, preventive measures such as reduced capsaicin consumption, H. pylori clearance, and DFMO treatment may lessen gastric cancer incidence.

Abstract Background: Gastric cancer risk evolves over time due to environmental, dietary, and lifestyle changes including Helicobacter pylori (H. pylori) infection and consumption of hot peppers (i.e. capsaicin). H. pylori infection promotes gastric mucosal injury in the early phase of capsaicin exposure. In addition, capsaicin consumption is reported to suppress immune function and increase host susceptibility to microbial infection. This relationship suggests a need to investigate the mechanism of how both H. pylori infection and capsaicin contribute to gastric inflammation and lead to gastric cancer. No previous experimental animal models have been developed to study this dual association. Here we developed a series of mouse models that progress from chronic gastritis to gastric cancer. C57-Balb/c mice were infected with the H. pylori (SS1) strain and then fed capsaicin (0.05% or 0.2g/kg/day) or not. Consequently, we investigated the association between H. pylori infection and capsaicin consumption during the initiation of gastric inflammation and the later development of gastric cancer. Tumor size and phenotype were analyzed to determine the molecular mechanism driving the shift from gastritis to stomach cancer. Gastric carcinogenesis was also prevented in these models using the ornithine decarboxylase inhibitor DFMO (2-difluoromethylornithine). Results: This study provides evidence showing that a combination of H. pylori infection and capsaicin consumption leads to gastric carcinogenesis. The transition from chronic gastritis to gastric cancer is mediated through interleukin-6 (IL-6) stimulation with an incidence rate of 50%. However, this progression can be prevented by treating with anti-inflammatory agents. In particular, we used DFMO to prevent gastric tumorigenesis by reducing inflammation and promoting recovery of disease-free stasis. The anti-inflammatory role of DFMO highlights the injurious effect of inflammation in gastric cancer development and the need to reduce gastric inflammation for cancer prevention. Conclusions: Overall, these mouse models provide reliable systems for analyzing the molecular mechanisms and synergistic effects of H. pylori and capsaicin on human cancer etiology. Accordingly, preventive measures like reduced capsaicin consumption, H. pylori clearance, and DFMO treatment can lessen gastric cancer incidence. Lastly, anti-inflammatory agents like DFMO can play important roles in prevention of inflammation-associated gastric cancer.