Abstract 12: Social isolation promotes mammary cancer recurrence, increases IL6/JAK/STAT3 signaling and causes mitochondrial dysfunction in tamoxifen treated rats, and a traditional herbal mixture reverses all these changes

Abstract Social isolation is associated with increased risk and mortality from many diseases, such as breast cancer. Socially isolated breast cancer survivors have a 43% higher risk of recurrence and a 64% higher risk of breast cancer-specific mortality than socially integrated survivors. Since Covid-19 has dramatically increased the incidence of social isolation, it is important to determine if social isolation affects the response to endocrine therapy and/or recurrence after the therapy is completed. Since previous studies indicate that social isolation increases circulating inflammatory cytokines, we investigated if an anti-inflammatory herbal mixture Jaeumkanghwa-tang (JGT) prevents the adverse effects of social isolation on breast cancer mortality. Estrogen receptor positive mammary tumors were initiated with 7,12-dimethylbenz[a]anthracene. When a rat developed a palpable mammary tumor, it was either socially isolated (SI) by housing it singly or a rat was allowed to remain group-housed (GH). Tamoxifen (340ppm via diet) or tamoxifen + JGT (500ppm via drinking water) started when the first mammary tumor reached a size of 11 mm in diameter. Tamoxifen administration ended when a complete response to this therapy had lasted for 9 weeks (corresponds to 5 years in women). During tamoxifen therapy, social isolation non-significantly reduced the rate of complete responses to 21%, from 31% in GH group (p>0.05). After the therapy was completed, SI significantly increased local mammary tumor recurrence (p<0.001; 45% GH vs 75% SI). RNAseq analysis was performed in the mammary glands. Gene set enrichment analysis (GSEA) of transcriptome showed that the increased recurrence risk in socially isolated rats was associated with an enrichment of IL6/JAK/STAT3 signaling: this result was confirmed in the tumors. In addition, oxidative phosphorylation (OXPHOS) pathway was suppressed: the suppressed genes included those involved in mitochondrial pyruvate transport and conversion of pyruvate to acetyl CoA as well as genes in the TCA cycle and mediating electron transport in mitochondrial complexes I-IV. Social isolation also increased the expression of inflammatory receptor for advanced glycation end-products (RAGE) (p≤0.05). Consumption of an anti-inflammatory JGT inhibited IL6/JAK/STAT3 signaling, upregulated OXPHOS signaling and prevented the increased risk of mammary cancer recurrence in socially isolated animals. The percentage of recurrences in the SI rats dropped from 75% without JGT to 22% with JGT (p<0.001). Breast cancer mortality among socially isolated survivors may be most effectively prevented by focusing on the period following endocrine therapy using tools that inhibit IL6/JAK/STAT3 inflammatory cytokine signaling and correct disrupted OXPHOS and mitochondrial dysfunction. Citation Format: Fabia de Oliveira Andrade, Lu Jin, Robert Clarke, Imani Wood, MaryAnn Dutton, Chezaray Anjorin, Grace Rubin, Audrey Gao, Surojeet Sengupta, Kevin FitzGerald, Leena Hilakivi-Clarke. Social isolation promotes mammary cancer recurrence, increases IL6/JAK/STAT3 signaling and causes mitochondrial dysfunction in tamoxifen treated rats, and a traditional herbal mixture reverses all these changes [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 12.