Genetically determined inflammatory-response related cytokine and chemokine transcript profiles between mammary carcinoma resistant and susceptible rat strains

Abstract

Multiple human breast and rat mammary carcinoma susceptibility (Mcs) alleles have been identified. Wistar Kyoto (WKY) rats are resistant to developing mammary carcinomas, while Wistar Furth (WF) females are susceptible. Gene transcripts at Mcs5a1, Mcs5a2, and Mcs5c are differentially expressed between resistant WKY and susceptible WF alleles in immune-system tissues. We hypothesized that immune-related gene transcript profiles are genetically determined in mammary carcinoma resistant and susceptible mammary glands. Low-density QPCR arrays were used to compare inflammation related genes between mammary carcinoma resistant WKY and susceptible WF females. Mammary gland gene transcript levels predicted to be different based on arrays were tested in independent samples. In total, 20 females per strain were exposed to 7,12-dimethylbenz(a)anthracene (DMBA) to induce mammary carcinogenesis. Twelve age-matched controls per strain without DMBA were included to determine main effects of DMBA-exposure. Significant (ANOVA P ≤ 0.01) effects of strain on mammary gland transcript level were observed for Cx3cl1, Il11ra, Il4, C3, Ccl20, Ccl11, Itgb2, Cxcl12, and Cxcr7. Significant effects of DMBA-exposure were observed for Cx3cl1, Il11ra, Cxcr4, Il4ra, and Il4. Strain and DMBA-exposure interaction effects were significant for Cx3cl1. Transcript levels of Cxcr7 relative to Cxcr4 were modified differently by DMBA in mammary carcinoma resistant and susceptible strains. In conclusion, several genetically-determined differences in cytokine, chemokine, and receptor gene transcript levels were identified between mammary carcinoma susceptible and resistant mammary glands, which may be indicative of cell populations and activities that suppress mammary carcinogenesis in resistant genotypes.

Figure 1. Inflammatory cytokine, chemokine, and receptor transcript levels in mammary carcinoma susceptible WF and resistant WKY mammary glands with DMBA and without

Graphed are means ± SEs of relative quantification (RQ) of genes indicated on x-axes. Rplp2 levels were used to standardize targets. Twenty females per strain were given DMBA, and twelve aged matched controls per strain were included. A, inflammatory cytokine, chemokine, and receptor mammary gland transcript levels in twelve week old mammary carcinoma susceptible WF (unfilled bars) and resistant WKY (filled bars) females with DMBA [+] or without [-]. B, strain by DMBA-exposure interactions were statistically significant for Cx3cl1 (P < 0.0001) and potentially significant for Cxcr7 (P = 0.0435). Compared to mammary cancer susceptible WF mammary glands (circles), Cx3cl1 expression was significantly higher in mammary glands from resistant WKY rats (squares) not exposed to DMBA (P = 0.0034). There was no difference in Cx3cl1 transcript level between strains in mammary carcinogen induced (DMBA +) females (P = 0.7483). Cxcr7 levels were significantly higher in mammary cancer resistant WKY rats (squares) compared susceptible WF females (circles) with DMBA (P = 0.0027), but not without (P = 0.4966). C, mammary gland Cxcr4 and Cxcr7 expression in DMBA-exposed (squares) and un-exposed (circles) females compared between mammary carcinoma resistant WKY and susceptible WF rat strains. Cxcr4 expression was higher than Cxcr7 in both strains (P = 0.0367 [WF] and 0.0606 [WKy]) when control females not exposed to mammary carcinogen were evaluated. Cxcr7 levels were significantly higher than Cxcr4 levels in the mammary cancer resistant strain (WKY) following DMBA exposure (P = 0.0059). Cxcr7 and Cxcr4 transcript levels were similar in mammary cancer susceptible WF females following DMBA exposure (P = 0.4673).