Neurotensin accelerates atherosclerosis and increases circulating levels of short-chain and saturated triglycerides.

BACKGROUND AND AIMS: Obesity and type 2 diabetes are significant risk factors for atherosclerotic cardiovascular disease (CVD) worldwide, but the underlying pathophysiological links are poorly understood. Neurotensin (NT), a 13-amino-acid hormone peptide, facilitates intestinal fat absorption and contributes to obesity in mice fed a high-fat diet. Elevated levels of pro-NT (a stable NT precursor produced in equimolar amounts relative to NT) are associated with obesity, type 2 diabetes, and CVD in humans. Whether NT is a causative factor in CVD is unknown. METHODS: Nt+/+ and Nt-/- mice were either injected with adeno-associated virus encoding PCSK9 mutants or crossed with Ldlr-/- mice and fed a Western diet. Atherosclerotic plaques were analyzed by en face analysis, Oil Red O and CD68 staining. In humans, we evaluated the association between baseline pro-NT and growth of carotid bulb thickness after 16.4 years. Lipidomic profiles were analyzed. RESULTS: Atherosclerotic plaque formation is attenuated in Nt-deficient mice through mechanisms that are independent of reductions in circulating cholesterol and triglycerides but associated with remodeling of the plasma triglyceride pool. An increasing plasma concentration of pro-NT predicts atherosclerotic events in coronary and cerebral arteries independent of all major traditional risk factors, indicating a strong link between NT and atherosclerosis. This plasma lipid profile analysis confirms the association of pro-NT with remodeling of the plasma triglyceride pool in atherosclerotic events. CONCLUSIONS: Our findings are the first to directly link NT to increased atherosclerosis and indicate the potential role for NT in preventive and therapeutic strategies for CVD.

Weighted mean difference statistics for paired data in the presence of missing values.

Missing data is a common issue in many biomedical studies. Under a paired design, some subjects may have missing values in either one or both of the conditions due to loss of follow-up, insufficient biological samples, etc. Such partially paired data complicate statistical comparison of the distribution of the variable of interest between the two conditions. In this article, we propose a general class of test statistics based on the difference in weighted sample means without imposing any distributional or model assumption. An optimal weight is derived from this class of tests. Simulation studies show that our proposed test with the optimal weight performs well and outperforms existing methods in practical situations. Two cancer biomarker studies are provided for illustration.

Integrin α6ß4 signals through DNA damage response pathway to sensitize breast cancer cells to cisplatin.

Integrin α6ß4 is highly expressed in triple negative breast cancer (TNBC) and drives its most aggressive traits; however, its impact on chemotherapeutic efficacy remains untested. We found that integrin α6ß4 signaling promoted sensitivity to cisplatin and carboplatin but not to other chemotherapies tested. Mechanistic investigations revealed that integrin α6ß4 stimulated the activation of ATM, p53, and 53BP1, which required the integrin ß4 signaling domain. Genetic manipulation of gene expression demonstrated that mutant p53 cooperated with integrin α6ß4 for cisplatin sensitivity and was necessary for downstream phosphorylation of 53BP1 and enhanced ATM activation. Additionally, we found that in response to cisplatin-induced DNA double strand break (DSB), integrin α6ß4 suppressed the homologous recombination (HR) activity and enhanced non-homologous end joining (NHEJ) repair activity. Finally, we discovered that integrin α6ß4 preferentially activated DNA-PK, facilitated DNA-PK-p53 and p53-53BP1 complex formation in response to cisplatin and required DNA-PK to enhance ATM, 53BP1 and p53 activation as well as cisplatin sensitivity. In summary, we discovered a novel function of integrin α6ß4 in promoting cisplatin sensitivity in TNBC through DNA damage response pathway.

Hydrogen Peroxide Promotes the Production of Radiation-Derived EVs Containing Mitochondrial Proteins.

In spite of extensive successes, cancer recurrence after radiation treatment (RT) remains one of the significant challenges in the cure of localized prostate cancer (PCa). This study focuses on elucidating a novel adaptive response to RT that could contribute to cancer recurrence. Here, we used PC3 cell line, an adenocarcinoma from a bone metastasis and radio-resistant clone 695 cell line, which survived after total radiation dose of 66 Gy (2 Gy × 33) and subsequently regrew in nude mice after exposure to fractionated radiation at 10 Gy (2 Gy × 5). Clone 695 cells not only showed an increase in surviving fraction post-radiation but also an increase in hydrogen peroxide (H2O2) production when compared to PC3 cells. At the single cell level, confocal microscope images coupled with IMARIS rendering software demonstrate an increase in mitochondrial mass and membrane potential in clone 695 cells. Utilizing the Seahorse XF96 instrument to investigate mitochondrial respiration, clone 695 cells demonstrated a higher basal Oxygen Consumption Rate (OCR), ATP-linked OCR, and proton leak compared to PC3 cells. The elevation of mitochondrial function in clone 695 cells is accompanied by an increase in mitochondrial H2O2 production. These data suggest that H2O2 could reprogram PCa's mitochondrial homeostasis, which allows the cancer to survive and regrow after RT. Upon exposure to RT, in addition to ROS production, we found that RT induces the release of extracellular vesicles (EVs) from PC3 cells (p < 0.05). Importantly, adding H2O2 to PC3 cells promotes EVs production in a dose-dependent manner and pre-treatment with polyethylene glycol-Catalase mitigates H2O2-mediated EV production. Both RT-derived EVs and H2O2-derived EVs carried higher levels of mitochondrial antioxidant proteins including, Peroxiredoxin 3, Glutathione Peroxidase 4 as well as mitochondrial-associated oxidative phosphorylation proteins. Significantly, adding isolated functional mitochondria 24 h prior to RT shows a significant increase in surviving fractions of PC3 cells (p < 0.05). Together, our findings reveal that H2O2 promotes the production of EVs carrying mitochondrial proteins and that functional mitochondria enhance cancer survival after RT.

Molecular Tumor Board-Assisted Care in an Advanced Cancer Population: Results of a Phase II Clinical Trial.

PURPOSE: Multidisciplinary molecular tumor boards (MTBs) interpret next-generation sequencing reports and help oncologists determine best therapeutic options; however, there is a paucity of data regarding their clinical utility. The purpose of this study was to determine if MTB-directed therapy improves progression-free survival (PFS) over immediately prior therapy in patients with advanced cancer. METHODS: This single-arm, prospective phase II clinical trial enrolled patients with advanced cancer with an actionable mutation who received MTB-recommended targeted therapy between January 1, 2017, and October 31, 2020. MTB-recommended both on-label (level 1 evidence) and off-label (evidence levels 2 and 3) therapies. Of the 93 enrolled patients, 43 were treated frontline and 50 received second-line or greater-line therapy. The primary outcome was the probability of patients treated with second-line or greater-line MTB-directed therapy who achieved a PFS ratio ≥ 1.3 (PFS on MTB-directed therapy divided by PFS on the patient's immediately prior therapy). Secondary outcomes included PFS for patients treated frontline and overall survival and adverse effects for the entire study population. RESULTS: The most common disease sites were lung (35 of 93, 38%), gynecologic (17 of 93, 18%), GI (16 of 93, 17%), and head and neck (7 of 93, 8%). The Kaplan-Meier estimate of the probability of PFS ratio ≥ 1.3 was 0.59 (95% CI, 0.47 to 0.75) for patients treated with second-line or greater-line MTB-directed therapy. The median PFS was 449 (range 42-1,125) days for patients treated frontline. The median overall survival was 768 (range 22-1,240) days. There were four nontreatment-related deaths. CONCLUSION: When treated with MTB-directed therapy, most patients experienced improved PFS compared with immediately prior treatment. MTB-directed targeted therapy may be a strategy to improve outcomes for patients with advanced cancer.

Tissue-Specific Downregulation of Fatty Acid Synthase Suppresses Intestinal Adenoma Formation via Coordinated Reprograming of Transcriptome and Metabolism in the Mouse Model of Apc-Driven Colorectal Cancer.

Altered lipid metabolism is a potential target for therapeutic intervention in cancer. Overexpression of Fatty Acid Synthase (FASN) correlates with poor prognosis in colorectal cancer (CRC). While multiple studies show that upregulation of lipogenesis is critically important for CRC progression, the contribution of FASN to CRC initiation is poorly understood. We utilize a C57BL/6-Apc/Villin-Cre mouse model with knockout of FASN in intestinal epithelial cells to show that the heterozygous deletion of FASN increases mouse survival and decreases the number of intestinal adenomas. Using RNA-Seq and gene set enrichment analysis, we demonstrate that a decrease in FASN expression is associated with inhibition of pathways involved in cellular proliferation, energy production, and CRC progression. Metabolic and reverse phase protein array analyses demonstrate consistent changes in alteration of metabolic pathways involved in both anabolism and energy production. Downregulation of FASN expression reduces the levels of metabolites within glycolysis and tricarboxylic acid cycle with the most significant reduction in the level of citrate, a master metabolite, which enhances ATP production and fuels anabolic pathways. In summary, we demonstrate the critical importance of FASN during CRC initiation. These findings suggest that targeting FASN is a potential therapeutic approach for early stages of CRC or as a preventive strategy for this disease.

Tumor Suppressor Par-4 Regulates Complement Factor C3 and Obesity.

Prostate apoptosis response-4 (Par-4) is a tumor suppressor that induces apoptosis in cancer cells. However, the physiological function of Par-4 remains unknown. Here we show that conventional Par-4 knockout (Par-4-/-) mice and adipocyte-specific Par-4 knockout (AKO) mice, but not hepatocyte-specific Par-4 knockout mice, are obese with standard chow diet. Par-4-/- and AKO mice exhibit increased absorption and storage of fat in adipocytes. Mechanistically, Par-4 loss is associated with mdm2 downregulation and activation of p53. We identified complement factor c3 as a p53-regulated gene linked to fat storage in adipocytes. Par-4 re-expression in adipocytes or c3 deletion reversed the obese mouse phenotype. Moreover, obese human subjects showed lower expression of Par-4 relative to lean subjects, and in longitudinal studies, low baseline Par-4 levels denoted an increased risk of developing obesity later in life. These findings indicate that Par-4 suppresses p53 and its target c3 to regulate obesity.

Ketogenesis Attenuates KLF5-Dependent Production of CXCL12 to Overcome the Immunosuppressive Tumor Microenvironment in Colorectal Cancer.

The dynamic composition of the tumor microenvironment (TME) can markedly alter the response to targeted therapies for colorectal cancer. Cancer-associated fibroblasts (CAF) are major components of TMEs that can direct and induce infiltration of immunosuppressive cells through secreted cytokines such as CXCL12. Ketogenic diets (KD) can inhibit tumor growth and enhance the anticancer effects of immune checkpoint blockade. However, the role of ketogenesis on the immunosuppressive TME is not known. Here, we show that decreased ketogenesis is a signature of colorectal cancer and that an increase in ketogenesis using a KD decreases CXCL12 production in tumors, serum, liver, and lungs. Moreover, increasing ketogenesis by overexpression of the ketogenic enzyme 3-hydroxy-3-methylglutaryl-CoA synthase 2 (HMGCS2) or treatment with the ketone body ß-hydroxybutyrate markedly decreased expression of KLF5, which binds the CXCL12 promoter and induces CXCL12 expression in CAFs. KD decreased intratumoral accumulation of immunosuppressive cells, increased infiltration of natural killer and cytotoxic T cells, and enhanced the anticancer effects of PD-1 blockade in murine-derived colorectal cancer. Furthermore, increasing ketogenesis inhibited colorectal cancer migration, invasion, and metastasis in vitro and in vivo. Overall, ketogenesis is downregulated in the colorectal cancer TME, and increased ketogenesis represses KLF5-dependent CXCL12 expression to improve the immunosuppressive TME, which leads to the enhanced efficacy of immunotherapy and reduced metastasis. Importantly, this work demonstrates that downregulation of de novo ketogenesis in the TME is a critical step in colorectal cancer progression. SIGNIFICANCE: This study identifies ketogenesis as a critical regulator of the tumor microenvironment in colorectal cancer and suggests the potential for ketogenic diets as a metabolic strategy to overcome immunosuppression and prolong survival. See related commentary by Montrose and Galluzzi, p. 1464.

Activation of Drp1 promotes fatty acids-induced metabolic reprograming to potentiate Wnt signaling in colon cancer.

Cancer cells are known for their ability to adapt variable metabolic programs depending on the availability of specific nutrients. Our previous studies have shown that uptake of fatty acids alters cellular metabolic pathways in colon cancer cells to favor fatty acid oxidation. Here, we show that fatty acids activate Drp1 to promote metabolic plasticity in cancer cells. Uptake of fatty acids (FAs) induces mitochondrial fragmentation by promoting ERK-dependent phosphorylation of Drp1 at the S616 site. This increased phosphorylation of Drp1 enhances its dimerization and interaction with Mitochondrial Fission Factor (MFF) at the mitochondria. Consequently, knockdown of Drp1 or MFF attenuates fatty acid-induced mitochondrial fission. In addition, uptake of fatty acids triggers mitophagy via a Drp1- and p62-dependent mechanism to protect mitochondrial integrity. Moreover, results from metabolic profiling analysis reveal that silencing Drp1 disrupts cellular metabolism and blocks fatty acid-induced metabolic reprograming by inhibiting fatty acid utilization. Functionally, knockdown of Drp1 decreases Wnt/ß-catenin signaling by preventing fatty acid oxidation-dependent acetylation of ß-catenin. As a result, Drp1 depletion inhibits the formation of tumor organoids in vitro and xenograft tumor growth in vivo. Taken together, our study identifies Drp1 as a key mediator that connects mitochondrial dynamics with fatty acid metabolism and cancer cell signaling.

Hematological adverse events in the management of glioblastoma.

BACKGROUND: Hematological adverse events (HAEs) are common during treatment for glioblastoma (GBM), usually associated with temozolomide (TMZ). Their clinical value is uncertain, as few investigations have focused on outcomes for HAEs during GBM treatment. METHODS: We combined data from two randomized clinical trials, RTOG 0525 and RTOG 0825, to analyze HAEs during treatment for GBM. We investigated differences between chemoradiation and adjuvant therapy, and by regimen received during adjuvant treatment. RESULTS: 1454 patients participated in these trials, of which 1154 (79.4%) developed HAEs. During chemoradiation, 44.4% of patients developed HAEs (54% involving more than one cell line), and were most commonly lymphopenia (50.6%), and thrombocytopenia (47.5%). During adjuvant treatment, 45% of patients presented HAEs (78.6% involving more than one cell line), and were more commonly leukopenia (62.7%), and thrombocytopenia (62.3%). Median overall survival (OS) and progression free survival (PFS) were longer in patients with HAEs (OS 19.4 months and PFS 9.9 months) compared to those with other or no adverse events (OS 14.1 months and PFS 5.9 months). There was no significant difference in survival between grade 1 and/or 2 versus grade 3 and/or 4 HAEs. History of HAEs during chemoradiation was a protective factor for presentation of HAEs during adjuvant therapy. CONCLUSION: HAEs are common during GBM treatment, and often involve more than one cell line (more likely during adjuvant therapy). HAEs may be associated with prolonged OS and PFS, particularly during adjuvant therapy. HAEs during chemoradiation was a protective factor for HAEs during adjuvant therapy.

Clinical Outcomes of Molecular Tumor Boards: A Systematic Review.

We conducted this systematic review to evaluate the clinical outcomes associated with molecular tumor board (MTB) review in patients with cancer. METHODS: A systematic search of PubMed was performed to identify studies reporting clinical outcomes in patients with cancer who were reviewed by an MTB. To be included, studies had to report clinical outcomes, including clinical benefit, response, progression-free survival, or overall survival. Two reviewers independently selected studies and assessed quality with the Quality Assessment Tool for Before-After (Pre-Post) Studies with No Control Group or the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies depending on the type of study being reviewed. RESULTS: Fourteen studies were included with a total of 3,328 patients with cancer. All studies included patients without standard-of-care treatment options and usually with multiple prior lines of therapy. In studies reporting response rates, patients receiving MTB-recommended therapy had overall response rates ranging from 0% to 67%. In the only trial powered on clinical outcome and including a control group, the group receiving MTB-recommended therapy had significantly improved rate of progression-free survival compared with those receiving conventional therapy. CONCLUSION: Although data quality is limited by a lack of prospective randomized controlled trials, MTBs appear to improve clinical outcomes for patients with cancer. Future research should concentrate on prospective trials and standardization of approach and outcomes.

Ketogenesis alleviates TNFα-induced apoptosis and inflammatory responses in intestinal cells.

The disturbance of strictly regulated self-regeneration in mammalian intestinal epithelium is associated with various intestinal disorders, particularly inflammatory bowel diseases (IBDs). TNFα, which plays a critical role in the pathogenesis of IBDs, has been reported to inhibit production of ketone bodies such as ß-hydroxybutyrate (ßHB). However, the role of ketogenesis in the TNFα-mediated pathological process is not entirely known. Here, we showed the regulation and role of HMGCS2, the rate-limiting enzyme of ketogenesis, in TNFα-induced apoptotic and inflammatory responses in intestinal epithelial cells. Treatment with TNFα dose-dependently decreased protein and mRNA expression of HMGCS2 and its product, ßHB production in human colon cancer cell lines HT29 and Caco2 cells and mouse small intestinal organoids. Moreover, the repressed level of HMGCS2 protein was found in intestinal epithelium of IBD patients with Crohn's disease and ulcerative colitis as compared with normal tissues. Furthermore, knockdown of HMGCS2 enhanced and in contrast, HMGCS2 overexpression attenuated, the TNFα-induced apoptosis and expression of pro-inflammatory chemokines (CXCL1-3) in HT29, Caco2 cells and DLD1 cells, respectively. Treatment with ßHB or rosiglitazone, an agonist of PPARγ, which increases ketogenesis, attenuated TNFα-induced apoptosis in the intestinal epithelial cells. Finally, HMGCS2 knockdown enhanced TNFα-induced reactive oxygen species (ROS) generation. In addition, hydrogen peroxide, the major ROS contributing to intestine injury, decreased HMGCS2 expression and ßHB production in the intestinal cells and mouse organoids. Our findings demonstrate that increased ketogenesis attenuates TNFα-induced apoptosis and inflammation in intestinal cells, suggesting a protective role for ketogenesis in TNFα-induced intestinal pathologies.

Role of AMPK and Akt in triple negative breast cancer lung colonization.

Triple negative breast cancer (TNBC) is an aggressive disease with a 5-y relative survival rate of 11% after distant metastasis. To survive the metastatic cascade, tumor cells remodel their signaling pathways by regulating energy production and upregulating survival pathways. AMP-activated protein kinase (AMPK) and Akt regulate energy homeostasis and survival, however, the individual or synergistic role of AMPK and Akt isoforms during lung colonization by TNBC cells is unknown. The purpose of this study was to establish whether targeting Akt, AMPKα or both Akt and AMPKα isoforms in circulating cancer cells can suppress TNBC lung colonization. Transient silencing of Akt1 or Akt2 dramatically decreased metastatic colonization of lungs by inducing apoptosis or inhibiting invasion, respectively. Importantly, transient pharmacologic inhibition of Akt activity with MK-2206 or AZD5363 inhibitors did not prevent colonization of lung tissue by TNBC cells. Knockdown of AMPKα1, AMPKα2, or AMPKα1/2 also had no effect on metastatic colonization of lungs. Taken together, these findings demonstrate that transient decrease in AMPK isoforms expression alone or in combination with Akt1 in circulating tumor cells does not synergistically reduce TNBC metastatic lung colonization. Our results also provide evidence that Akt1 and Akt2 expression serve as a bottleneck that can challenge colonization of lungs by TNBC cells.

Neurotensin differentially regulates bile acid metabolism and intestinal FXR-bile acid transporter axis in response to nutrient abundance.

Studies demonstrate a role for neurotensin (NT) in obesity and related comorbidities. Bile acid (BA) homeostasis alterations are associated with obesity. We determined the effect of NT on BA metabolism in obese and non-obese conditions. Plasma and fecal BA profiles were analyzed by LC-MS/MS in male and female NT+/+ and NT-/- mice fed low-fat (LFD) or high-fat diet (HFD) for 6 weeks (early stage of obesity) or greater than 20 weeks (late stage of obesity). The nuclear farnesoid X receptor (FXR) and BA transporter mRNA expression were assessed in ileum, mouse enteroids, and human cell lines. HFD decreased plasma primary and secondary BAs in NT+/+ mice; HFD-induced decrease of plasma BAs was improved in NT-deficient mice. In NT+/+ mice, HFD inhibited ileal FXR and BA transporter expression; HFD-decreased expression of FXR and BA transporters was prevented in NT-/- mice. Compared with LFD-fed NT+/+ mice, LFD-fed NT-/- mice had relatively lower levels of ileal FXR and BA transporter expression. Moreover, NT stimulates the expression of FXR and BA transporters in Caco-2 cells; however, stimulated expression of BA transporters was attenuated in NT-/- enteroids. Therefore, we demonstrate that HFD disrupts the BA metabolism and ileal FXR and BA transporter axis which are improved in the absence of NT, suggesting that NT contributes to HFD-induced disruption of BA metabolism and plays an inhibitory role in the regulation of ileal FXR and BA transporter signaling under obese conditions. Conversely, NT positively regulates the expression of ileal FXR and BA transporters under non-obese conditions. Therefore, NT plays a dual role in obese and non-obese conditions, suggesting possible therapeutic strategies for obesity control.

Regulation of SIRT2 by Wnt/ß-catenin signaling pathway in colorectal cancer cells.

Activation of the Wnt/ß-catenin pathway is one of the hallmarks of colorectal cancer (CRC). Sirtuin 2 (SIRT2) protein has been shown to inhibit CRC proliferation. Previously, we reported that SIRT2 plays an important role in the maintenance of normal intestinal cell homeostasis. Here, we show that SIRT2 is a direct target gene of Wnt/ß-catenin signaling in CRC cells. Inhibition or knockdown of Wnt/ß-catenin increased SIRT2 promoter activity and mRNA and protein expression, whereas activation of Wnt/ß-catenin decreased SIRT2 promoter activity and expression. ß-Catenin was recruited to the promoter of SIRT2 and transcriptionally regulated SIRT2 expression. Wnt/ß-catenin inhibition increased mitochondrial oxidative phosphorylation (OXPHOS) and CRC cell differentiation. Moreover, inhibition of OXPHOS attenuated the differentiation of CRC cells induced by Wnt/ß-catenin inhibition. In contrast, inhibition or knockdown of SIRT2 decreased, while overexpression of SIRT2 increased, OXPHOS activity and differentiation in CRC cells. Consistently, inhibition or knockdown or SIRT2 attenuated the differentiation induced by Wnt/ß-catenin inhibition. These results demonstrate that SIRT2 is a novel target gene of the Wnt/ß-catenin signaling and contributes to the differentiation of CRC cells.

High plasma levels of pro-NT are associated with increased colon cancer risk.

Emerging data supports a potential role of neurotensin (NT) in the development of obesity, obesity-associated comorbidities, and certain cancers. The association of NT with colon cancer risk has not been explicitly explored. We determined plasma levels of pro-NT, a stable NT precursor fragment, in 223 incident colon cancer patients and 223 age-, gender-, BMI-matched population controls participating in a population-based case-control study of colon cancer. On average, the cases have significantly higher levels of pro-NT than the controls (median = 205.6 pmol/L vs 183.1 pmol/L, respectively; P = 0.02). Multivariate logistic regression models, adjusted for age, gender, BMI, family history of colorectal cancer, smoking, diabetes mellitus, alcohol, and non-steroidal anti-inflammatory drugs use, show statistically significant risk associations: for continuous measure of pro-NT, the OR estimate was 1.30 (95% CI =1.03-1.64; P = 0.026) for each increment of 175 pmol/L; for dichotomized measure of pro-NT, the OR estimate was 1.75 (95% CI = 1.12-2.74; P = 0.025) for those in the top quartile comparing to the other participants. Our results support circulating levels of pro-NT as a novel risk biomarker for colon cancer.

Inhibition of protein tyrosine phosphatase receptor type F suppresses Wnt signaling in colorectal cancer.

Wnt signaling dysregulation promotes tumorigenesis in colorectal cancer (CRC). We investigated the role of PTPRF, a receptor-type tyrosine phosphatase, in regulating Wnt signaling in CRC. Knockdown of PTPRF decreased cell proliferation in patient-derived primary colon cancer cells and established CRC cell lines. In addition, the rate of proliferation as well as colony formation ability were significantly decreased in tumor organoids grown in 3D, whereas the number of differentiated tumor organoids were markedly increased. Consistently, knockdown of PTPRF resulted in a decrease in the expression of genes associated with cancer stem cells downstream of Wnt/ß-catenin signaling. Treating PTPRF knockdown cells with GSK3 inhibitor rescued the expression of Wnt target genes suggesting that PTPRF functions upstream of the ß-catenin destruction complex. PTPRF was found to interact with LRP6 and silencing PTPRF largely decreased the activation of LRP6. Interestingly, this PTPRF-mediated activation of Wnt signaling was blocked in cells treated with clathrin endocytosis inhibitor. Furthermore, knockdown of PTPRF inhibited xenograft tumor growth in vivo and decreased the expression of Wnt target genes. Taken together, our studies identify a novel role of PTPRF as an oncogenic protein phosphatase in supporting the activation of Wnt signaling in CRC.

Upregulation of CPT1A is essential for the tumor-promoting effect of adipocytes in colon cancer.

Colon tumors grow in an adipose tissue-enriched microenvironment. Locally advanced colon cancers often invade into surrounding adipose tissue with a direct contact with adipocytes. We have previously shown that adipocytes promote tumor growth by modulating cellular metabolism. Here we demonstrate that carnitine palmitoyltransferase I (CPT1A), a key enzyme controlling fatty acid oxidation (FAO), was upregulated in colon cancer cells upon exposure to adipocytes or fatty acids. In addition, CPT1A expression was increased in invasive tumor cells within the adipose tissue compared to tumors without direct contact with adipocytes. Silencing CPT1A abolished the protective effect provided by fatty acids against nutrient deprivation and reduced tumor organoid formation in 3D culture and the expression of genes associated with cancer stem cells downstream of Wnt/ß-catenin. Mechanistically, CPT1A-dependent FAO promoted the acetylation and nuclear translocation of ß-catenin. Furthermore, knockdown of CPT1A blocked the tumor-promoting effect of adipocytes in vivo and inhibited xenograft tumor initiation. Taken together, our findings identify CPT1A-depedent FAO as an essential metabolic pathway that enables the interaction between adipocytes and colon cancer cells.

Inhibition of Fatty Acid Synthase Upregulates Expression of CD36 to Sustain Proliferation of Colorectal Cancer Cells.

Fatty acid synthase, a key enzyme of de novo lipogenesis, is an attractive therapeutic target in cancer. The novel fatty acid synthase inhibitor, TVB-3664, shows anti-cancer activity in multiple cancers including colorectal cancer; however, it is unclear whether uptake of exogeneous fatty acids can compensate for the effect of fatty acid synthase inhibition. This study demonstrates that inhibition of fatty acid synthase selectively upregulates fatty acid translocase (CD36), a fatty acid transporter, in multiple colorectal cancer models including colorectal cancer cells with shRNA mediated knockdown of fatty acid synthase and genetically modified mouse tissues with heterozygous and homozygous deletion of fatty acid synthase. Furthermore, human colorectal cancer tissues treated with TVB-3664 show a significant and selective upregulation of CD36 mRNA. shRNA-mediated knockdown of CD36 and inhibition of CD36 via sulfosuccinimidyl oleate, a chemical inhibitor of CD36, decreased cell proliferation in vitro and reduced tumor growth in subcutaneous xenograft models. Isogenic cell populations established from patient derived xenografts and expressing high levels of CD36 show a significantly increased ability to grow tumors in vivo. The tumor-promoting effect of CD36 is associated with an increase in the levels of pAkt and survivin. Importantly, combinatorial treatment of primary and established colorectal cancer cells with TVB-3664 and sulfosuccinimidyl oleate shows a synergistic effect on cell proliferation. In summary, our study demonstrates that upregulation of CD36 expression is a potential compensatory mechanism for fatty acid synthase inhibition and that inhibition of CD36 can improve the efficacy of fatty acid synthase-targeted therapy.

Targeting PI3K and AMPKα Signaling Alone or in Combination to Enhance Radiosensitivity of Triple Negative Breast Cancer.

Triple negative breast cancer (TNBC) is the most aggressive breast cancer subtype and is characterized by poor survival. Radiotherapy plays an important role in treating TNBC. The purpose of this study was to determine whether inhibiting the AMP-activated protein kinase (AMPK) and phosphatidylinositol 3-kinase (PI3K) pathways alone or in combination potentiates radiotherapy in TNBC. AMPKα1 and AMPKα2 knockdown diminished cyclin D1 expression and induced G1 cell cycle arrest but did not induce apoptosis alone or in combination with radiotherapy. Next, we analyzed the role of PI3K p85α, p85ß, p110α, p110ß, Akt1, and Akt2 proteins on TNBC cell cycle progression and apoptosis induction. Akt1 and p110α knockdown diminished cyclin D1 expression and induced apoptosis. Silencing Akt1 promoted synergistic apoptosis induction during radiotherapy and further reduced survival after radiation. Treatment with the Akt inhibitor, MK-2206 48 h after radiotherapy decreased Akt1 levels and potentiated radiation-induced apoptosis. Together, our results demonstrate that AMPKα, p110α, and Akt1 promote TNBC proliferation and that Akt1 is a key regulator of radiosensitivity in TNBC. Importantly, combining radiotherapy with the pharmacological inhibition of Akt1 expression is a potentially promising approach for the treatment of TNBC.