Western diet enhances benzo(a)pyrene-induced colon tumorigenesis in a polyposis in rat coli (PIRC) rat model of colon cancer

Consumption of Western diet (WD), contaminated with environmental toxicants, has been implicated as one of the risk factors for sporadic colon cancer. Our earlier studies using a mouse model revealed that compared to unsaturated dietary fat, the saturated dietary fat exacerbated the development of colon tumors caused by B(a)P. The objective of this study was to study how WD potentiates B(a)P-induced colon carcinogenesis in the adult male rats that carry a mutation in the Apc locus - the polyposis in the rat colon (PIRC) rats. Groups of PIRC rats were fed with AIN-76A standard diet (RD) or Western diet (WD) and received 25, 50, or 100 μg B(a)P/kg body weight (wt) via oral gavage for 60 days. Subsequent to exposure, rats were euthanized; colons were retrieved and preserved in 10% formalin for counting the polyp numbers, measuring the polyp size, and histological analyses. Blood samples were collected and concentrations of cholesterol, triglycerides, glucose, insulin and leptin were measured. Rats that received WD + B(a)P showed increased levels of cholesterol, triglycerides, and leptin in comparison to RD + B(a)P groups or controls. The colon tumor numbers showed a B(a)P dose-response relationship. Adenomas with high grade dysplasia were prominent in B(a)P + WD rats compared to B(a)P + RD rats and controls (p < 0.05). The larger rat model system used in this study allows for studying more advanced tumor phenotypes over a longer duration and delineating the role of diet - toxicant interactions in sporadic colon tumor development.

Butyrate regulates the expression of inflammatory and chemotactic cytokines in human acute leukemic cells during apoptosis

Butyrate is a histone deacetylase inhibitor implicated in many studies as a potential therapy for various forms of cancer. High concentrations of butyrate (>1.5mM) have been shown to activate apoptosis in several cancer cell lines including prostate, breast, and leukemia. Butyrate is also known to influence multiple signaling pathways that are mediators of cytokine production. The purpose of this study was to evaluate the impact of high concentrations of butyrate on the cancer microenvironment vis-à-vis apoptosis, cellular migration, and capacity to modulate cytokine expression in cancer cells. The results indicate that high concentrations of butyrate induced a 2-fold activation of caspase-3 and reduced cell viability by 60% in U937 leukemia cells. Within 24h, butyrate significantly decreased the levels of chemokines CCL2 and CCL5 in HL-60 and U937 cells, and decreased CCL5 in THP-1 leukemia cells. Differential effects were observed in treatments with valproic acid for CCL2 and CCL5 indicating butyrate-specificity. Many of the biological effects examined in this study are linked to activation of the AKT and MAPK signaling pathways; therefore, we investigated whether butyrate alters the levels of phosphorylated forms of these signaling proteins and how it correlated with the expression of chemokines. The results show that butyrate may partially regulate CCL5 production via p38 MAPK. The decrease in p-ERK1/2 and p-AKT levels correlated with the decrease in CCL2 production. These data suggest that while promoting apoptosis, butyrate has the potential to influence the cancer microenvironment by inducing differential expression of cytokines.

Common gamma chain cytokines in combinatorial immune strategies against cancer

Common γ chain (γC) cytokines, namely IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21 are important for the proliferation, differentiation, and survival of lymphocytes that display antitumor activity, thus stimulating considerable interest for the use of cytokines in cancer immunotherapy. In this review, we will focus on the γC cytokines that demonstrate the greatest potential for immunotherapy, IL-2, IL-7, IL-15, and IL-21. We will briefly cover their biological function, potential applications in cancer therapy, and update on their use in combinatorial immune strategies for eradicating tumors and hematopoietic malignancies.

Abstract 142: Sodium butyrate suppresses production of chemokines in human U937 cells

Sodium butyrate (NaB) is a sodium salt of butyric acid. It is a HDAC inhibitor implicated in many studies as a potential therapy for various forms of cancer. Due to its ability to promote total and gamma globin during erythroid differentiation, low concentrations (&lt;1.5 mM) of NaB are considered a potential therapy for hemoglobin disorders including sickle cell diseases, leukemia, and β-thalassemia. Previously, high concentrations of NaB (&gt;1.5 mM) have been shown to activate apoptosis in several cancer cell lines including prostate, endometrial, breast and leukemia. Low concentrations of NaB influence multiple signaling pathways that are known mediators of cytokine production. However, it is not known whether high concentrations alter these pathways having the capacity to modulate cytokine expression in cancer cells and alter the cancer microenvironment, which is the purpose of this study. We exposed U937 leukemia cells to NaB at 5 or 10 mM doses for various time points. The culture media of the cells were harvested and analyzed by Human Multi-Analyte Cytokine ELISArray for levels of chemokines and chemotactic properties via migration assay. As evidence of apoptosis, we monitored cells for caspase-3 activation and cell viability. Our results indicate NaB induces a 2-fold activation of caspase-3 but a decrease in cell viability by 60%. Also, NaB induces a significant decrease in levels of chemokines CCL2 and CCL5 in 24 hours. Moreover, monocyte migration towards culture media from NaB treated cells, decreased in time-dependent manner. To elucidate the signaling mechanism(s) used by NaB (5mM), we investigated whether NaB alters the phospho-protein levels of AKT, ERK1/2, p38 and JNK. We observed an increase in phosphorylation of p38 MAPK, but a decrease in ERK1/2 in response to NaB. Also, there was an initial decrease in p-AKT level within 2 minutes suggesting a decline of Akt activation. However, this was followed by re-activation of AKT by 24 hours post-treatment. Interestingly, NaB did not influence activation of JNK. This data suggests that while promoting apoptosis, NaB has the potential to influence cancer microenvironment by inducing differential expression of cytokines. While the mechanism by which NaB induces differential expression of cytokines remains unknown, potentially, it could occur via the AKT and/or MAPK mediated pathways. These effects may influence the biology of normal and cancer cells thereby altering the status of the patient receiving NaB therapy. *Pulliam is supported by NHLBI T32 Pre-doctoral training grant #2-T32-HL007735-16 to Dr. Adunyah and CTSA award #UL1TR000445 from the National Center for Advancing Translational Sciences. Additionally, Dr. Adunyah is supported by NCI Cancer Partnership U54 grant #5-U54-CA163069-02 and NIMHD MeTRC grant #8-U54-MD007593-04. The content is solely the responsibility of the authors and does not necessarily represent the official views of the NIH.

Citation Format: Stephanie R. Pulliam, Roland Cooper, Samuel E. Adunyah. Sodium butyrate suppresses production of chemokines in human U937 cells. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 142. doi:10.1158/1538-7445.AM2014-142

Abstract 1583: Western diet enhances benzo(a)pyrene [B(a)P]-induced colon tumorigenesis in the PIRC rat model via proinflammatory mechanisms

Colorectal cancer ranks third in terms of mortalities in the United States. Consumption of Western Diet (rich in red meat and fats), contaminated with environmental toxicants such as benzo(a)pyrene [B(a)P] has also been implicated as one of the causative factors for sporadic colon cancer. Therefore, the objective of this study was to investigate the effect of dietary fat type on B(a)P -induced colon cancer in an adult male rat model, the Polyposis In the Rat Colon (PIRC) kindred type. Groups of PIRC rats (n = 5) were fed with AIN-76A regular diet (RD) or Western diet (WD) and these rats also received 25, 50 and 100 µg B(a)P/kg body wt., daily via oral gavage for a period of 60 days. Rats that were fed with the diets alone, but no B(a)P served as controls. Food consumption and body weights of the rats were periodically monitored. Subsequent to exposure, rats were sacrificed; colons, liver and other tissues were retrieved and preserved in 10% formalin for observation of gross pathological changes. Blood samples were collected and concentrations of cholesterol, triglycerides, and adiponectin were measured. Colon tissues were scored for tumors, and preserved in 10% formalin for observation of pathological changes. Colon and liver samples were analyzed for activation of drug metabolizing enzymes (DMEs) CYP1A1, CYP1B1 and GST. The lack of change in food consumption notwithstanding, body weight loss of WD group compared to RD group and controls (p &lt; 0.05) was noticed. An increased incidence of adenomas and high grade dysplasia were encountered in rats that were fed with WD compared to RD and controls (p &lt; 0.05). The colon tumor counts were more in B(a)P + WD rats compared to their B(a)P + RD counterparts, and also exhibited a B(a)P dose-response relationship, with 100 µg B(a)P/kg registering greater counts. Adenomas with high grade dysplasia were prominent in B(a)P + WD rats compared to B(a)P + RD rats. Immunohistochemical analyses of colon tissue samples for PCNA, cyclin D1, TGF-β, and β-catenin revealed increased levels of cell proliferation and nuclear positivity among all treatment groups. Rats that received B(a)P + WD showed increased levels of cholesterol and triglycerides in comparison to rats that received B(a)P + RD and also controls. Levels of adiponectin did not vary much between B(a)P + WD, and B(a)P + RD groups. Western diet consumption increased DME activation among rats that were given B(a)P + WD with marked increase in rats that were administered 100 µg/kg B(a)P + WD (p &lt; 0.05) compared to other treatment groups. Our results demonstrate that WD accelerates the development of colon tumors induced by B(a)P through proinflammatory action, characterized by gain in tumor number and sizes, and body weight loss.

Citation Format: Kelly L. Harris, Stephanie R. Pulliam, Mohammad S. Niaz, Mary K. Washington, Samuel E. Adunyah, Aramandla Ramesh. Western diet enhances benzo(a)pyrene [B(a)P]-induced colon tumorigenesis in the PIRC rat model via proinflammatory mechanisms. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1583. doi:10.1158/1538-7445.AM2014-1583