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Background: Previously, we found low-carbohydrate diets slowed prostate cancer (PC) growth and increased survival vs. a Western diet in mice, by inhibiting the insulin/IGF-1 axis. Thus, we tested whether modifying carbohydrate qualityto lower glycemic index (GI) without changing quantityresults in similar benefits as with reduced quantity. Methods: Male SCID mice injected with LAPC-4 cells were single-housed and randomized when their tumors reached 200 mm3on average to a LoGI (48% carbohydrate kcal, from Hylon-VII) or HiGI Western diet (48% carbohydrate kcal, from sucrose). Body weight and tumor volume were measured weekly. Body composition was assessed 35 days after randomization. Blood glucose and serum insulin, IGF-1 and IGFBP3 were measured at study end when tumor volumes reached 800 mm3. We analyzed gene expression of mice tumors by RNA-sequencing and human tumors using the Prostate Cancer Transcriptome Atlas. Results: There were no significant differences in tumor volume (P> 0.05), tumor proliferation (P= 0.29), and overall survival (P= 0.15) between groups. At 35 days after randomization, the LoGI group had 30% lower body fat (P= 0.007) despite similar body weight (P= 0.58). At sacrifice, LoGI mice had smaller livers (P< 0.001) and lower glucose (P= 0.15), insulin (P= 0.11), IGF-1 (P= 0.07) and IGF-1:IGFBP3 ratio (P= 0.05), and higher IGFBP3 (P= 0.09) vs. HiGI, although none of these metabolic differences reached statistical significance. We observed differential gene expression and pathway enrichment in mice tumors by diet. The most upregulated and downregulated gene in the LoGI group showed expression patterns more closely resembling expression in human benign prostate tissue vs. PC. Conclusions: In this single mouse xenograft model, consuming a low GI diet did not delay PC growth or survival vs. a high GI diet despite suggestions of decreased activation of the insulin/IGF-1 pathway. These data suggest that improving carbohydrate quality alone while consuming a high carbohydrate diet may not effectively slow PC growth.

Serine/threonine kinase 3 (STK3) is an essential member of the highly conserved Hippo tumor suppressor pathway that regulates Yes-associated protein 1 (YAP1) and TAZ. STK3 and its paralog STK4 initiate a phosphorylation cascade that regulates YAP1/TAZ inhibition and degradation, which is important for regulated cell growth and organ size. Deregulation of this pathway leads to hyperactivation of YAP1 in various cancers. Counter to the canonical tumor suppression role of STK3, we report that in the context of prostate cancer (PC), STK3 has a pro-tumorigenic role. Our investigation started with the observation that STK3, but not STK4, is frequently amplified in PC. Additionally, high STK3 expression is associated with decreased overall survival and positively correlates with androgen receptor (AR) activity in metastatic castrate-resistant PC. XMU-MP-1, an STK3/4 inhibitor, slowed cell proliferation, spheroid growth, and Matrigel invasion in multiple models. Genetic depletion of STK3 decreased proliferation in several PC cell lines. In a syngeneic allograft model, STK3 loss slowed tumor growth kinetics in vivo, and biochemical analysis suggests a mitotic growth arrest phenotype. To further probe the role of STK3 in PC, we identified and validated a new set of selective STK3 inhibitors, with enhanced kinase selectivity relative to XMU-MP-1, that inhibited tumor spheroid growth and invasion. Consistent with the canonical role, inhibition of STK3 induced cardiomyocyte growth and had chemoprotective effects. Our results indicate that STK3 has a non-canonical role in PC progression and that inhibition of STK3 may have a therapeutic potential for PC that merits further investigation.

Some, but not all, epidemiologic evidence supports a role for cholesterol, the precursor for steroid hormone synthesis, in prostate cancer. Using a PTEN-null transgenic mouse model of prostate cancer, we tested the effect of modifying serum cholesterol levels on prostate tumor development and growth. We hypothesized that serum cholesterol reduction would lower tumor androgens and slow prostate cancer growth. PTENloxP/loxP-Cre+mice consuming ad libitum high fat, high cholesterol diets (40% fat, 1.25% cholesterol) were randomized after weaning to receive the cholesterol uptake inhibitor, ezetimibe (30 mg/kg/day), or no intervention, and sacrificed at 2, 3, or 4 months of age. Serum cholesterol and testosterone were measured by ELISA and intraprostatic androgens by mass spectrometry. Prostate histology was graded, and proliferation and apoptosis in tumor epithelium and stroma was assessed by Ki67 and TUNEL, respectively. Ezetimibe-treated mice had lower serum cholesterol at 4 months (p= 0.031). Serum cholesterol was positively correlated with prostate weight (p= 0.033) and tumor epithelial proliferation (p= 0.069), and negatively correlated with tumor epithelial apoptosis (p= 0.004). Serum cholesterol was unrelated to body weight (p= 0.195). Tumor stromal cell proliferation was reduced in the ezetimibe group (p= 0.010). Increased serum cholesterol at 4 months was associated with elevated intraprostatic DHEA, testosterone, and androstenedione (p= 0.043, p= 0.074, p= 0.031, respectively). However, cholesterol reduction did not significantly affect adenocarcinoma development at 2, 3, or 4 months of age (0, 78, and 100% in ezetimibe-treated vs. 0, 80, and 100% in mice not receiving ezetimibe). Though serum cholesterol reduction did not significantly affect the rate of adenocarcinoma development in the PTEN-null transgenic mouse model of prostate cancer, it lowered intraprostatic androgens and slowed tumor growth. These findings support a role for serum cholesterol in promoting prostate cancer growth, potentially via enhanced tumor androgen signaling, and may provide new insight into cholesterol-lowering interventions for prostate cancer treatment.

Streams in the Hondo River basin (Mexico–Belize) face ecological disturbances caused by use of fertilizers and pesticides, as well as invasion by exotic species. These threats can affect ecosystem functioning, with loss of biotic integrity. Mass-balance trophic models were developed to quantify the energy flow and assess the maturity and health states for three locations in the basin, in two seasons. Quantitative sampling was carried out for plankton, fish, macrobenthos, insects, benthic autotrophs, detritus, and exported organic matter. Field sampling was supplemented with a literature review to define functional groups and their diets. Results showed that more than 50% of the energy flow originated from detritus, which suggests that the systems are bottom-up controlled. Low values of energy transfer efficiency, connectivity, omnivory, recycling, mean path length, and ascendency suggest that the freshwater bodies in this basin are oligotrophic, but they are not in a good health and thus have low stability and are susceptible to disturbance, despite the fact that they also have a high number of specialized functional groups, indicative of a well-organized food web, supposed to be representative of healthy ecosystems. The potential of these models to manage shallow tropical streams is discussed.

S-phase kinase-associated protein 2 (Skp2) functions as the receptor component of the Skp–Cullin–F-box complex and is implicated in the degradation of several cell cycle regulators, such as p21Cip1, p27Kip1, p57Kip2, and cyclin E. Numerous studies in human and experimental tumors have demonstrated low p27Kip1levels and elevated Skp2 expression. However, a direct association between the inverse correlation of Skp2 and p27Kip1with tumorigenesis has not been demonstrated. Herein, we provide evidence that skin tumorigenesis is inhibited in Skp2−/−mice. An analysis of mouse keratinocytes indicates that increased p27Kip1levels in Skp2−/−epidermis cause reduced cell proliferation that is alleviated in the epidermis from Skp2−/−/p27−/−compound mice. In contrast, we establish that a p27Kip1deficiency does not overturn the reduced skin tumorigenesis experienced by Skp2−/−mice. In addition, Skp2−/−epidermis exhibits an accumulation of p53-cofactor CBP/p300 that is associated with elevated apoptosis in hair follicles and decreased skin tumorigenesis. We conclude that p27Kip1accumulation is responsible for the hypoplasia observed in normal tissues of Skp2−/−mice but does not have a preponderant function in reducing skin tumorigenesis.

The proto-oncogene c-Mycencodes a transcription factor that is implicated in the regulation of cellular proliferation, differentiation, and apoptosis. Mycaccelerates the rate of cell proliferation, at least in part, through its ability to down-regulate the expression of the cell cycle inhibitor p27Kip1. Moreover, p27Kip1protein levels are regulated by ubiquitin-mediated turnover, leading to destruction by the E3 ubiquitin ligase SCFSkp2. Therefore, we hypothesize that a lack of Skp2 expression should lead to increased p27Kip1levels and further inhibition of Myc-mediated proliferation and tumorigenesis. Mycexpression in epithelial tissues of transgenic mice (K5-Myc) led to increased keratinocyte proliferation and the development of spontaneous tumors within the oral cavity. We generated K5-Myc–transgenic mice in an Skp2-null background. Consistent with our hypothesis, we found that Myc-mediated keratinocyte hyperproliferation was abolished by the loss of Skp2. However, Skp2 ablation did not affect Myc-driven tumorigenesis because the incidence, latency, and degree of differentiation of oral tumors were identical between K5-Myc/Skp2+/+and K5-Myc/Skp2−/−mice. Altogether, these findings suggest that Skp2 and p27Kip1are critical for Myc-driven keratinocyte proliferation; however, Myc-mediated tumorigenesis in the oral epithelium is independent of the Skp2-p27Kip1axis.

It has been widely assumed that elevated CDK2 kinase activity plays a contributory role in tumorigenesis. We have previously shown that mice overexpressing CDK4 under control of the keratin 5 promoter (K5CDK4 mice) develop epidermal hyperplasia and increased susceptibility to squamous cell carcinomas. In this model, CDK4 overexpression results in increased CDK2 activity associated with the noncatalytic function of CDK4, sequestration of p21Cip1and p27Kip1. Furthermore, we have shown that ablation of Cdk2 reduces Ras-Cdk4 tumorigenesis, suggesting that increased CDK2 activity plays an important role in Ras-mediated tumorigenesis. To investigate this hypothesis, we generated two transgenic mouse models of elevated CDK2 kinase activity, K5Cdk2 and K5Cdk4D158Nmice. The D158N mutation blocks CDK4 kinase activity without interfering with its binding capability. CDK2 activation via overexpression of CDK4D158N, but not of CDK2, resulted in epidermal hyperplasia. We observed elevated levels of p21Cip1in K5Cdk2, but not in K5Cdk4D158N, epidermis, suggesting that CDK2 overexpression elicits a p21Cip1response to maintain keratinocyte homeostasis. Surprisingly, we found that neither CDK2 overexpression nor the indirect activation of CDK2 enhanced skin tumor development. Thus, although the indirect activation of CDK2 is sufficient to induce keratinocyte hyperproliferation, activation of CDK2 alone does not induce malignant progression in Ras-mediated tumorigenesis.