Characterizing the Role of Calcium Sensing Receptor in the Progression of Obesity-Mediated Aggressive Prostate Cancer Phenotype

Obesity increases the risk of advanced prostate cancer (PCa). The calcium sensing receptor (CaSR) has been shown to be responsive to obesity-mediated cytokines and is upregulated in metastatic PCa. This study used a novel in vitro approach, involving the exposure of PCa cells to sera, from obese or normal weight males, and to CaSR inhibitor NPS-2143. Cell viability was determined using MTT assay. MMP-9 activity and invasion were assessed using zymography and invasion chambers, respectively. Microscopy was used to visualize EMT proteins. qRT-PCR and immunoblot analysis were used to quantify changes in genes and proteins important for tumorigenesis. Exposure to obese sera increased the proliferation, and the invasive capacity of PCa cells and de-localized epithelial-mesenchymal transition markers, which were attenuated with CaSR inhibition. Exposure to obese sera upregulated mRNA expression of PTHrP and protein expression of COX-2, IL-6, and CaSR. Inhibition of CaSR downregulated the mRNA expression of PTHrP and RANK, and protein expression of pERK and TNF-α. Obesity was shown to increase invasion and upregulate the expression of genes and proteins involved in PCa tumorigenesis. CaSR inhibition downregulated the expression of several of these factors. Thus, CaSR is a potentially important protein to target in obesity-mediated PCa progression.

Inhibition of PI3K/Akt and ERK signaling decreases visfatin-induced invasion in liver cancer cells

OBJECTIVES

Visfatin is found in adipose tissue and is referred to as nicotinamide phosphoribosyltransferase (Nampt). Visfatin has anti-apoptotic, proliferative, and metastatic properties and may mediate its effects via ERK and PI3K/Akt signaling. Studies have yet to determine whether inhibition of kinase signaling will suppress visfatin-induced liver cancer. The purpose of this study was to determine which signaling pathways visfatin may promote liver cancer progression.

METHODS

HepG2 and SNU-449 liver cancer cells were exposed to visfatin with or without ERK or PI3K/Akt inhibitor, or both inhibitors combined. These processes that were assessed: proliferation, reactive oxygen species (ROS), lipogenesis, invasion, and matrix metalloproteinase (MMP).

RESULTS

Inhibition of PI3K/Akt and combination of inhibitors suppressed visfatin-induced viability. ERK inhibition in HepG2 cells decreased visfatin-induced proliferation. ERK inhibitor alone or in combination with PI3K inhibitors effectively suppressed MMP-9 secretion and invasion in liver cancer cells. PI3K and ERK inhibition and PI3K inhibition alone blocked visfatin's ROS production in SNU-449 cells. These results corresponded with a decrease in phosphorylated Akt and ERK, β-catenin, and fatty acid synthase.

CONCLUSIONS

Akt and ERK inhibition differentially regulated physiological changes in liver cancer cells. Inhibition of Akt and ERK signaling pathways suppressed visfatin-induced invasion, viability, MMP-9 activation, and ROS production.

The role of visfatin and resistin in an in vitro model of obesity-induced invasive liver cancer

Obesity is associated with the development of liver disease and its progression to hepatocellular carcinoma. This link may be attributed to adipocytokines such as visfatin and resistin which have been shown to promote liver cancer incidence and progression. Studies have yet to determine the role of visfatin and resistin in liver cancer, specifically in the context of obesity. The objective of this study was to investigate the effect of neutralizing visfatin and resistin in obese (OB) or normal weight (NW) sera to determine the contribution of these proteins in obesity-induced invasive liver cancer. Sera from OB or NW males was used to determine the efficacy of neutralizing visfatin and resistin to reduce the obesity-induced liver cancer phenotype. HepG2 and SNU-449 cells were exposed to OB and NW sera ± antibodies for visfatin or resistin. The neutralizing antibodies differentially suppressed invasion, reactive oxygen species production, and matrix metalloproteinase-9 secretion. These changes corresponded with a decrease in phosphorylated extracellular signal-regulated kinases and protein kinase B in HepG2 cells, but differences were not observed in CAP1 or β-catenin. In conclusion, visfatin and resistin have differential roles in obesity-associated liver cancer and may be potential targets to reverse the impact of obesity on liver cancer progression.

Silibinin Differentially Decreases the Aggressive Cancer Phenotype in an In Vitro Model of Obesity and Prostate Cancer

Aim: Obesity increases the risk for aggressive and fatal prostate cancer (PCa). The bioactive compound silibinin has been researched for its chemopreventative properties and may benefit obese or overweight individuals with PCa.Methods: This study used an in vitro model of obesity exposing prostate cancer cells to sera from obese, overweight, or normal weight males with or without the addition of silibinin. Molecular activity was assayed as well as the phenotype of PCa cells with various treatments.Results: Obesity increased the expression of proliferative signaling including COX-2, IL-6, AKT, ERK, and AR, which was attenuated with silibinin. Cell growth, and invasive capacity of prostate cancer cells was increased with obese and overweight sera, and silibinin was able to mitigate this affect. However, there are limitations to this study in that an in vivo model was not used to validate these in vitro results nor a co-culture model, which may better recapitulate the tumor microenvironment.Conclusions: Silibinin may be a safe intervention for those with or at risk for prostate cancer, and it may be the most beneficial for obese or overweight males.

Characterizing the differential physiological effects of adipocytokines visfatin and resistin in liver cancer cells

Background Obesity, a major public health concern, increases the risk of developing liver cancer which is the leading cause of cancer-related deaths worldwide. Obesity is associated with increased adiposity and macrophage infiltration both of which promote secretion of adipokines and cytokines in the tumor microenvironment. Specifically, visfatin and resistin have been detected at higher levels in the serum of obese individuals and liver tumors. However, the contribution of these adipocytokines in the progression of liver cancer remains unclear. Materials and methods The objective of this study was to characterize the effects of visfatin and resistin on HepG2, SNU-449 and HuH7 liver cancer cells. Cells exposed to visfatin and resistin were analyzed for fatty acid synthase protein, and phosphorylation of Akt and ERK tumorigenic signaling pathways, cell viability, lipogenesis, reactive oxygen species (ROS), matrix metallopeptidase 9 (MMP-9) enzyme activity and invasion. Results HepG2, SNU-449, and HuH7 liver cancer cells treated with visfatin and resistin increased cell viability, invasion, FASN protein, and Akt and ERK phosphorylation. Visfatin and resistin selectively increased ROS production in HepG2 and SNU-449 cells while there was no statistical difference in HuH7 cells. Visfatin and resistin stimulated lipogenesis in HepG2 cells while visfatin increased lipogenesis in SNU-449 cells, and visfatin nor resistin had an effect on lipogenesis in HuH7 cells. Lastly, visfatin and resistin increased MMP-9 enzyme activity in HepG2 and HuH-7 cells but only visfatin increased MMP-9 activity in SNU-449 cells. Conclusions Future studies are needed to determine if inhibition of ERK and Akt suppresses the visfatin and resistin-induced invasive liver cancer phenotype.

Effects of Obesity on the Regulation of Macrophage Population in the Prostate Tumor Microenvironment

Obesity is associated with a greater risk of prostate cancer mortality. However, the mechanisms connecting obesity to the progression of prostate cancer remain unknown. This study determined the impact of obesity on macrophage recruitment and tumor-associated macrophage (TAM) polarization in the prostate tumor microenvironment, since a high concentration of TAMs in tumors has been linked to progression in prostate cancer. We utilized an in vitro model in which pre-adipocytes, prostate cancer cells, and macrophages were exposed to sera from obese or nonobese men, or conditioned media generated under obese or nonobese conditions. Matrigel invasion chambers were used to assess macrophage recruitment in vitro, and immunohistochemical analysis evaluated recruitment in a PTEN knockout mouse model. qPCR was used to measure mRNA levels of CCL2, COX-2, IL-10, TGF-beta, VEGF-A, arginase-1, and MMP-9. PGE2 production was measured by ELISA. Obesity increased macrophage and TAM recruitment, and increased mRNA levels of TAM markers in macrophages. Similarly, obese conditions increased CCL2 and COX-2 expression, as well as PGE2 levels in prostate cancer cells. COX-2 inhibition resulted in lower expression of obesity-induced TAM markers. Our data suggest that obesity promotes macrophage infiltration into the prostate tumor microenvironment, and induces TAM polarization through the COX-2/PGE2 pathway.

NSAID use reduces breast cancer recurrence in overweight and obese women: role of prostaglandin-aromatase interactions

Obesity is associated with a worse breast cancer prognosis and elevated levels of inflammation, including greater cyclooxygenase-2 (COX-2) expression and activity in adipose-infiltrating macrophages. The product of this enzyme, the proinflammatory eicosanoid prostaglandin E2 (PGE2), stimulates adipose tissue aromatase expression and subsequent estrogen production, which could promote breast cancer progression. This study demonstrates that daily use of a nonsteroidal anti-inflammatory drug (NSAID), which inhibits COX-2 activity, is associated with reduced estrogen receptor α (ERα)-positive breast cancer recurrence in obese and overweight women. Retrospective review of data from ERα-positive patients with an average body mass index of >30 revealed that NSAID users had a 52% lower recurrence rate and a 28-month delay in time to recurrence. To examine the mechanisms that may be mediating this effect, we conducted in vitro studies that utilized sera from obese and normal-weight patients with breast cancer. Exposure to sera from obese patients stimulated greater macrophage COX-2 expression and PGE2 production. This was correlated with enhanced preadipocyte aromatase expression following incubation in conditioned media (CM) collected from the obese-patient, sera-exposed macrophages, an effect neutralized by COX-2 inhibition with celecoxib. In addition, CM from macrophage/preadipocyte cocultures exposed to sera from obese patients stimulated greater breast cancer cell ERα activity, proliferation, and migration compared with sera from normal-weight patients, and these differences were eliminated or reduced by the addition of an aromatase inhibitor during CM generation. Prospective studies designed to examine the clinical benefit of NSAID use in obese patients with breast cancer are warranted.

Docosahexaenoic acid selectively induces human prostate cancer cell sensitivity to oxidative stress through modulation of NF-κB

BACKGROUND

Oxidative burden is strongly implicated in the pathogenesis of age-related diseases, including prostate cancer tumor formation. As omega-3 fatty acids possess known antioxidant properties, we investigated the effects of docosahexaenoic acid (DHA-22:6n-3), one component of fish oil, in modulating the effects of oxidative DNA damage in LNCaP and PacMetUT1 human prostate adenocarcinoma cells and in a normal human prostate cell line, PrEC.

METHODS

Cell survival was determined by an inhibition of colony formation assay. DNA double-strand breaks, NF-κB subcellular localization and relative survivin expression levels were determined by immunofluorescence and survivin expression levels confirmed by immunoblot assay. Measurement of NF-κB transcriptional activity was investigated by dual luciferase assay.

RESULTS

LNCaP and PacMetUT1 cells pretreated with DHA and pulsed with 32 µM H(2) O(2) exhibit decreased survival compared to PrEC. γ-H2AX foci, indicating DNA double-strand breaks, were associated with translocation of NF-κB into the nucleus, whereas exposure to DHA prior to H(2) O(2) treatment prevented NF-κB translocation. Further, DHA attenuated H(2) O(2) -induced NF-κB transcriptional activity and diminished expression of the downstream target, survivin.

CONCLUSIONS

NF-κB is heavily implicated in promoting prosurvival signaling and may be critical for resistance to the chronic oxidative stress observed in the pathogenesis of prostate cancer. Our studies indicate that exposure of cells to physiologically achievable levels of DHA prior to treatment with H(2) O(2) results in decreased cancer cell survival which is associated with nuclear exclusion of NF-κB. We therefore propose that DHA selectively sensitizes prostate cancer cells to growth arrest through attenuation of the NF-κB survival pathway.

Abstract 971: Obesity initiates a self-perpetuating inflammatory response in LNCaP prostate cancer cells

Background: Obesity increases prostate cancer (PCa) mortality but the mechanism remains unclear. Obesity induced chronic inflammation may be an important factor in advanced PCa. Studies have shown a local inflammatory microenvironment can promote prostate tumorigenesis. Obese men with advanced PCa have high levels of cytokines in their prostate and plasma. Clinical studies promoting weight loss in obese PCa patients have not demonstrated significant benefit in reducing disease progression, suggesting that once initiated, progression is self-sustaining. The role of obesity in stimulating the release of inflammatory autocrine factors in PCa cells and its effect on metastasis remains unclear. Previously, we have shown PCa cells exposed to obese sera increased migration, invasion, proliferation, MMP -9 activity and changes in EMT markers. Our aim was to determine whether PCa cells sustain an inflammatory response initiated by obesity and autocrine factors secreted by PCa cells sustain the metastatic phenotype shown in our previous studies. We hypothesize obesity initiates a self-perpetuating inflammatory response in PCa cells increasing metastatic potential.

Methods: We developed an in vitro model which mimics the systemic effect of obesity. 6 week old C57bl/6 male mice were fed a diet induced obesity chow (60% calories from fat) or control chow (10% calories from fat). After 12 weeks, mice were sacrificed, sera was collected and used for in vitro studies. To determine if the initial effects of obesity on PCa invasion are sustained by soluble factors secreted by PCa cells, we treated LNCaP cells with obese or control sera for 30 minutes. Treatments were replaced with serum free media for 18 hours. After 18 hours, conditioned media (CM) was harvested and used for in vitro studies. Cytokine protein array was used to detect a cytokines in conditioned media. Biological assays were used to investigate the effect of conditioned media on invasion, changes in EMT markers, proliferation and cell migration.

Results: After stimulation with obese sera, PCa cells secreted high levels of cytokines that mediate inflammatory processes including CCL2, IL-6, IL-8, Rantes and SDF-1. PCa cells treated with obese-stimulated CM resulted in a 2-fold increase in invasive capacity. Obese-stimulated CM resulted in a dispersion of e-cadherin from the cell membrane and nuclear translocation of β-catenin. CM from cells treated with obese sera modulated migration and proliferation promoting an aggressive prostate cancer phenotype.

Conclusion: PCa cells treated with obese sera sustain an inflammatory response in the absence of sera. Autocrine factors secreted by obesity treated cells sustain the metastatic phenotype similar to that of PCa cells treated directly with obese sera. The preliminary results from these in vitro studies warrant further in vivo research into the role of weight loss either through diet or exercise on PCa progression.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 971. doi:10.1158/1538-7445.AM2011-971