Commensal bacteria and fungi differentially regulate tumor responses to radiation therapy.

Studies suggest that the efficacy of cancer chemotherapy and immunotherapy is influenced by intestinal bacteria. However, the influence of the microbiome on radiation therapy is not as well understood, and the microbiome comprises more than bacteria. Here, we find that intestinal fungi regulate antitumor immune responses following radiation in mouse models of breast cancer and melanoma and that fungi and bacteria have opposite influences on these responses. Antibiotic-mediated depletion or gnotobiotic exclusion of fungi enhances responsiveness to radiation, whereas antibiotic-mediated depletion of bacteria reduces responsiveness and is associated with overgrowth of commensal fungi. Further, elevated intratumoral expression of Dectin-1, a primary innate sensor of fungi, is negatively associated with survival in patients with breast cancer and is required for the effects of commensal fungi in mouse models of radiation therapy.

Repeated transplantation of allogeneic cardiosphere-derived cells boosts therapeutic benefits without immune sensitization in a rat model of myocardial infarction.

BACKGROUND: A single dose of allogeneic cardiosphere-derived cells (CDCs) improves cardiac function and reduces scarring, and increases viable myocardium in the infarcted rat and pig heart without eliciting a detrimental immune response. Clinical trials using single doses of allogeneic human CDCs are underway. It is unknown whether repeat dosing confers additional benefit or if it elicits an immune response. METHODS: Wistar-Kyoto rats underwent coronary artery ligation and intramyocardial injection of CDCs, with a second thoracotomy and repeat CDC injection 3 weeks later. Treatment permutations included 2 doses of allogeneic Brown-Norway CDCs (n = 24), syngeneic Wistar-Kyoto CDCs (n = 24), xenogeneic human CDCs (n = 24) or saline (n = 8). Cardiac function was assessed by transthoracic echocardiography, infarct size and inflammatory infiltration by histology, and cellular and humoral immune responses by lymphocyte proliferation and alloantibody assays. RESULTS: Repeat dosing of allogeneic and syngeneic CDCs improved ejection fraction by 5.2% (95% CI 2.1 to 8.3) and 6.8% (95% CI 3.8 to 9.8) after the first dose, and by 3.4% (95% CI 0.1% to 6.8%) and 6.4% (95% CI 4.2% to 8.6%) after the second dose. Infarct size was equally reduced with repeat dosing of syngeneic and allogeneic CDCs relative to xenogeneic and control treatments (p < 0.0001). Significant rejection-like infiltrates were present only in the xenogeneic group; likewise, lymphocyte proliferation and antibody assays were positive in the xenogeneic and negative in syngeneic and allogeneic groups. CONCLUSIONS: Repeat dosing of allogeneic CDCs in immunocompetent rats is safe and effective, consistent with the known immunomodulatory and anti-inflammatory properties of CDCs. These findings motivate clinical testing of repeatedly dosed CDCs for chronic heart disease.

Cathelicidin suppresses colon cancer development by inhibition of cancer associated fibroblasts.

BACKGROUND: Cathelicidin (LL-37 in humans and mCRAMP in mice) represents a family of endogenous antimicrobial and anti-inflammatory peptides. Cancer-associated fibroblasts can promote the proliferation of colon cancer cells and growth of colon cancer tumors. METHODS: We examined the role of cathelicidin in the development of colon cancer, using subcutaneous human HT-29 colon-cancer-cell-derived tumor model in nude mice and azoxymethane- and dextran sulfate-mediated colon cancer model in C57BL/6 mice. We also determined the indirect antitumoral mechanism of cathelicidin via the inhibition of epithelial-mesenchymal transition (EMT) of colon cancer cells and fibroblast-supported colon cancer cell proliferation. RESULTS: Intravenous administration of cathelicidin expressing adeno-associated virus significantly reduced the size of tumors, tumor-derived collagen expression, and tumor-derived fibroblast expression in HT-29-derived subcutaneous tumors in nude mice. Enema administration of the mouse cathelicidin peptide significantly reduced the size and number of colonic tumors in azoxymethane- and dextran sulfate-treated mice without inducing apoptosis in tumors and the adjacent normal colonic tissues. Cathelicidin inhibited the collagen expression and vimentin-positive fibroblast expression in colonic tumors. Cathelicidin did not directly affect HT-29 cell viability, but did significantly reduce tumor growth factor-ß1-induced EMT of colon cancer cells. Media conditioned by the human colonic CCD-18Co fibroblasts promoted human colon cancer HT-29 cell proliferation. Cathelicidin pretreatment inhibited colon cancer cell proliferation mediated by media conditioned by human colonic CCD-18Co fibroblasts. Cathelicidin disrupted tubulin distribution in colonic fibroblasts. Disruption of tubulin in fibroblasts reduced fibroblast-supported colon cancer cell proliferation. CONCLUSION: Cathelicidin effectively inhibits colon cancer development by interfering with EMT and fibroblast-supported colon cancer cell proliferation.