Histamine Receptors Are Altered in Colorectal Cancer

Background: Histamine is an endogenous amine that acts on a wide variety of cell types throughout the body. Its activity is mediated by four distinct receptors: HRH1, HRH2, HRH3 and HRH4. Each of these receptors induces a distinct signaling cascade that has diverse output. Histamine has been postulated to influence cancer progression, but little is known about the distribution of histamine receptors in the gut epithelium or its exact role in colorectal cancer. The aim of this study was to define the distribution of histamine receptors in the colonic epithelium in the setting of health and cancer. Methods & Results: We utilized publicly available single cell sequencing databases to examine the distribution of histamine receptors in the normal colon. We found that HRH1 was highly expressed in all colonic epithelial cells. Interestingly, HRH2, HRH3 and HRH4 were not expressed in any cell type in the colon. To confirm these findings, we grew human colonic organoids and found by qPCR analysis that HRH1 was the only receptor present in this epithelial specific system. In the setting of cancer, we found that HRH1 was elevated in colorectal cancer tumors compared to normal controls. Immunostaining of a tissue array confirmed that colon cancer tissue specimens had higher concentrations of immune associated HRH1; suggesting that immune cells were contributing to the higher levels of HRH1 observed in tumors. Single cell RNAseq data demonstrated that macrophages and monocytes had the highest expression of HRH1 among immune cells. Examination of immune infiltration and HRH1 expression in the Cancer Genome Atlas revealed a positive correlation between monocyte and macrophage HRH1 expression. Conclusions: These data suggest that HRH1 is the only receptor expressed in the colonic epithelium and that in cancer, infiltration of monocytes and macrophages harboring HRH1 elevate overall expression levels of this receptor in tumors. DDRC Pilot and Feasibility Award (Amy Engevik) Career Development Award (K01) (Amy Engevik) DK121869-01. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.