Impact of adding the multikinase inhibitor sorafenib to endocrine therapy in metastatic estrogen receptor-positive breast cancer.

BACKGROUND: Targeting growth factor and survival pathways may delay endocrine-resistance in estrogen receptor-positive breast cancer. MATERIALS & METHODS: A pilot Phase II study adding sorafenib to endocrine therapy in 11 patients with metastatic estrogen receptor-positive breast cancer was conducted. Primary end point was response by RECIST after 3 months of sorafenib. Secondary end points included safety, time to progression and biomarker modulation. The study closed early owing to slow accrual. RESULTS: Eight out of 11 patients had progressive disease on study entry and three had stable disease. Of the ten evaluable patients, seven experienced stable disease (70%) and three experienced progressive diseas (30%), with a median time to progression of 6.1 months (8.4 months in the seven patients on tamoxifen). The serum samples demonstrated a significant reduction in VEGF receptor 2 and PDGF receptor-α. Microarray analysis identified 32 suppressed genes, no induced genes and 29 enriched Kyoto Encyclopedia of Genes and Genomes pathways. CONCLUSION: The strategy of adding a targeted agent to endocrine therapy upon resistance may be worthwhile testing in larger studies.

Elevating PLK1 overcomes BETi resistance in prostate cancer via triggering BRD4 phosphorylation-dependent degradation in mitosis.

Bromodomain-containing protein 4 (BRD4) has emerged as a promising therapeutic target in prostate cancer (PCa). Understanding the mechanisms of BRD4 stability could enhance the clinical response to BRD4-targeted therapy. In this study, we report that BRD4 protein levels are significantly decreased during mitosis in a PLK1-dependent manner. Mechanistically, we show that BRD4 is primarily phosphorylated at T1186 by the CDK1/cyclin B complex, recruiting PLK1 to phosphorylate BRD4 at S24/S1100, which are recognized by the APC/CCdh1 complex for proteasome pathway degradation. We find that PLK1 overexpression lowers SPOP mutation-stabilized BRD4, consequently rendering PCa cells re-sensitized to BRD4 inhibitors. Intriguingly, we report that sequential treatment of docetaxel and JQ1 resulted in significant inhibition of PCa. Collectively, the results support that PLK1-phosphorylated BRD4 triggers its degradation at M phase. Sequential treatment of docetaxel and JQ1 overcomes BRD4 accumulation-associated bromodomain and extra-terminal inhibitor (BETi) resistance, which may shed light on the development of strategies to treat PCa.

Deregulation of Wnt/ß-catenin signaling through genetic or epigenetic alterations in human neuroendocrine tumors.

Carcinoid tumors are rare neuroendocrine tumors (NETs) that are increasing in incidence. Mutation and altered expression of Wnt/ß-catenin signaling components have been described in many tumors but have not been well-studied in NETs. Here, we observed accumulation of ß-catenin in the cytoplasm and/or nucleus in 25% of clinical NET tissues. By mutational analysis, the mutations of ß-catenin (I35S) and APC (E1317Q, T1493T) were identified in NET cells and the tissues. Expression of representative Wnt inhibitors was absent or markedly decreased in BON, a human pancreatic carcinoid cell line; treatment with 5-aza-2'-deoxycytidine (5-aza-CdR) increased expression levels of the Wnt inhibitors. Methylation analyses demonstrated that CpG islands of SFRP-1 and Axin-2 were methylated, whereas the promoters of DKK-1, DKK-3 and WIF-1 were unmethylated in four NET cells. Aberrant methylation of SFRP-1 was particularly observed in most of clinical NET tissues. In addition, the repression of these unmethylated genes was associated with histone H3 lysine 9 dimethylation (H3K9me2) in BON cells. Together, 5-aza-CdR treatment inhibited cell proliferation and decreased the protein levels of H3K9me2 and G9a. Moreover, a novel G9a inhibitor, UNC0638, suppressed BON cell proliferation through inhibition of Wnt/ß-catenin pathway. Overexpression of the inhibitory genes, particularly SFRP-1 and WIF-1 in BON cells, resulted in suppression of anchorage-independent growth and inhibition of tumor growth in mice. Our findings suggest that aberrant Wnt/ß-catenin signaling, through either mutations or epigenetic silencing of Wnt antagonists, contributes to the pathogenesis and growth of NETs and have important clinical implications for the prognosis and treatment of NETs.

Regulation of the potential marker for intestinal cells, Bmi1, by ß-catenin and the zinc finger protein KLF4: implications for colon cancer.

B lymphoma Mo-MLV insertion region 1 (Bmi1) is a Polycomb Group (PcG) protein important in gene silencing. It is a component of Polycomb Repressive Complex 1 (PRC1), which is required to maintain the transcriptionally repressive state of many genes. Bmi1 was initially identified as an oncogene that regulates cell proliferation and transformation, and is important in hematopoiesis and the development of nervous systems. Recently, it was reported that Bmi1 is a potential marker for intestinal stem cells. Because Wnt signaling plays a key role in intestinal stem cells, we analyzed the effects of Wnt signaling on Bmi1 expression. We found that Wnt signaling indeed regulates the expression of Bmi1 in colon cancer cells. In addition, the expression of Bmi1 in human colon cancers is significantly associated with nuclear ß-catenin, a hallmark for the activated Wnt signaling. Krüppel-like factor 4 (KLF4) is a zinc finger protein highly expressed in the gut and skin. We recently found that KLF4 cross-talks with Wnt/ß-catenin in regulating intestinal homeostasis. We demonstrated that KLF4 directly inhibits the expression of Bmi1 in colon cancer cells. We also found that Bmi1 regulates histone ubiquitination and is required for colon cancer proliferation in vitro and in vivo. Our findings further suggest that Bmi1 is an attractive target for cancer therapeutics.

Human epidermal growth factor receptor 2 expression in women with uterine cervix adenocarcinoma from Appalachian Kentucky.

Introduction: High-risk human epidermal growth factor receptor 2 (HER2)-positive adenocarcinomas associate with early recurrence and death, prompting consideration of novel radiotherapeutic options like a trastuzumab-linked thorium-227 alpha-particle emitting radionuclide. Methods: We conducted a retrospective pilot biomarker study of uterine cervix cancers among patients in Appalachian Kentucky, to characterize an exploitable triage biomarker like HER2 expression before starting a prospective phase 0 trial. Results: Most (60%) adenocarcinomas showed HER2 cell-surface overexpression, whereas squamous cell carcinomas (4%) did not do so. Discussion: Further validation tests of HER2 expression as a triage biomarker for radiopharmaceutical selection are warranted.

Human gastrin- releasing peptide receptor expression in women with uterine cervix cancer.

Introduction: 212Pb-DOTAM-GRPR1 is a pharmaceutical radioimmunoconjugate consisiting of an α-particle-emitting radionuclide lead-212 (212Pb), a metal chelator DOTAM (1,4,7,10-tetrakis(carbamoylmethyl)-1,4,7,10-tetraazacyclododecane), and a gastrin-releasing peptide receptor (GRPR)-targeted antagonist currently being evaluated as therapy in uterine cervix and other cancer types. Previous studies have revealed that a variable proportion of uterine cervix cancer tumors overexpress the radiopharmaceutical target GRPR when assessed by cell proportion and staining intensity immunoreactive scores (IRS). Tumor response to 212Pb-DOTAM-GRPR1 strongly associates with GRPR overexpression, and therefore, it seems reasonable to assess uterine cervix cancer GRPR immunoreactivity for greater insight into the feasibility of using 212Pb-DOTAM-GRPR1 as a radiopharmaceutical treatment. Methods: We examined a series of 33 uterine cervix cancer paraffin-embedded tumors in order to establish whether this tumor type overexpresses GRPR at an IRS score of 6 or higher, as 212Pb-DOTAM-GRPR1 is currently being evaluated in clinical trials against tumors showing such a level of expression. Results: The results show that five of five (100%) primary adenocarcinomas and 10 of 16 (63%) primary squamous cell tumors overexpress GRPR at an IRS score of 6 or higher. Discussion: The frequency of overexpression in this study suggests that 212Pb-DOTAM-GRPR1 radiopharmaceutical treatment may be useful in the management of persistent, recurrent, or metastatic uterine cervix cancer patients. A phase I clinical trial involving patients with metastatic uterine cervix cancer is currently underway (NCT05283330).

Glycolytic Regulation of Intestinal Stem Cell Self-Renewal and Differentiation.

BACKGROUND AND AIMS: The intestinal mucosa undergoes a continual process of proliferation, differentiation, and apoptosis. An imbalance in this highly regimented process within the intestinal crypts is associated with several intestinal pathologies. Although metabolic changes are known to play a pivotal role in cell proliferation and differentiation, how glycolysis contributes to intestinal epithelial homeostasis remains to be defined. METHODS: Small intestines were harvested from mice with specific hexokinase 2 (HK2) deletion in the intestinal epithelium or LGR5+ stem cells. Glycolysis was measured using the Seahorse XFe96 analyzer. Expression of phospho-p38 mitogen-activated protein kinase, the transcription factor atonal homolog 1, and intestinal cell differentiation markers lysozyme, mucin 2, and chromogranin A were determined by Western blot, quantitative real-time reverse transcription polymerase chain reaction, or immunofluorescence, and immunohistochemistry staining. RESULTS: HK2 is a target gene of Wnt signaling in intestinal epithelium. HK2 knockout or inhibition of glycolysis resulted in increased numbers of Paneth, goblet, and enteroendocrine cells and decreased intestinal stem cell self-renewal. Mechanistically, HK2 knockout resulted in activation of p38 mitogen-activated protein kinase and increased expression of ATOH1; inhibition of p38 mitogen-activated protein kinase signaling attenuated the phenotypes induced by HK2 knockout in intestinal organoids. HK2 knockout significantly decreased glycolysis and lactate production in intestinal organoids; supplementation of lactate or pyruvate reversed the phenotypes induced by HK2 knockout. CONCLUSIONS: Our results show that HK2 regulates intestinal stem cell self-renewal and differentiation through p38 mitogen-activated protein kinase/atonal homolog 1 signaling pathway. Our findings demonstrate an essential role for glycolysis in maintenance of intestinal stem cell function.

Cell-based quantification of chronic wasting disease prions.

Cell-based measurement of prion infectivity is currently restricted to experimental strains of mouse-adapted scrapie. Having isolated cell cultures with susceptibility to prions from diseased elk, we describe a modification of the scrapie cell assay allowing evaluation of prions causing chronic wasting disease, a naturally occurring transmissible spongiform encephalopathy. We compare this cervid prion cell assay to bioassays in transgenic mice, the only other existing method for quantification, and show this assay to be a relatively economical and expedient alternative that will likely facilitate studies of this important prion disease.

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.

Accelerated high fidelity prion amplification within and across prion species barriers.

Experimental obstacles have impeded our ability to study prion transmission within and, more particularly, between species. Here, we used cervid prion protein expressed in brain extracts of transgenic mice, referred to as Tg(CerPrP), as a substrate for in vitro generation of chronic wasting disease (CWD) prions by protein misfolding cyclic amplification (PMCA). Characterization of this infectivity in Tg(CerPrP) mice demonstrated that serial PMCA resulted in the high fidelity amplification of CWD prions with apparently unaltered properties. Using similar methods to amplify mouse RML prions and characterize the resulting novel cervid prions, we show that serial PMCA abrogated a transmission barrier that required several hundred days of adaptation and subsequent stabilization in Tg(CerPrP) mice. While both approaches produced cervid prions with characteristics distinct from CWD, the subtly different properties of the resulting individual prion isolates indicated that adaptation of mouse RML prions generated multiple strains following inter-species transmission. Our studies demonstrate that combined transgenic mouse and PMCA approaches not only expedite intra- and inter-species prion transmission, but also provide a facile means of generating and characterizing novel prion strains.

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.

Cutaneous pharmacologic cAMP induction induces melanization of the skin and improves recovery from ultraviolet injury in melanocortin 1 receptor-intact or heterozygous skin.

Homozygous loss of function of the melanocortin 1 receptor (MC1R) is associated with a pheomelanotic pigment phenotype and increased melanoma risk. MC1R heterozygosity is less well studied, although individuals inheriting one loss-of-function MC1R allele are also melanoma-prone. Using the K14-Scf C57BL/6J animal model whose skin is characterized by lifelong retention of interfollicular epidermal melanocytes like that of the human, we studied pigmentary, UV responses, and DNA repair capacity in the skin of variant Mc1r background. Topical application of forskolin, a skin-permeable pharmacologic activator of cAMP induction to mimic native Mc1r signaling, increased epidermal eumelanin levels, increased the capacity of Mc1r-heterozygous skin to resist UV-mediated inflammation, and enhanced the skin's ability to clear UV photolesions from DNA. Interestingly, topical cAMP induction also promoted melanin accumulation, UV resistance, and accelerated clearance in Mc1r fully intact skin. Together, our findings suggest that heterozygous Mc1r loss is associated with an intermediately melanized and DNA repair-proficient epidermal phenotype and that topical cAMP induction enhances UV resistance in Mc1r-heterozygous or Mc1r-wild-type individuals by increasing eumelanin deposition and by improving nucleotide excision repair.

Evaluation of antioxidant network proteins as novel prognostic biomarkers for head and neck cancer patients.

OBJECTIVES: Recurrence rates for head and neck squamous cell carcinoma (HNSCC) approach 50% at 5 years. Current staging fails to identify patients with a worse prognosis who might benefit from intensified treatment, which warrants improved prognostic biomarkers. The purpose of this retrospective case study is to identify potential prognostic biomarkers in patients with HNSCC including APE1 (DNA repair/redox gene regulator), NRF2 and PPARGC1A (redox gene regulators), SOD3 and DCN (antioxidant proteins). MATERIALS AND METHODS: Differential protein expression between benign, carcinoma in situ (CIS), and invasive HNSCC tissue specimens from 77 patients was assessed using immunohistochemistry. Protein expression was analyzed with multivariate, pair-wise, and Kaplan-Meier survival analyses to identify potential prognostic biomarkers. Utilizing The Cancer Genome Atlas's transcriptome database, pair-wise and survival analysis was performed to identify potential prognostic biomarkers. RESULTS: APE1, NRF2, PPARGC1A, SOD3, and DCN expression in HNSCC in relation to, lymph node invasion, and patient survival were examined. Elevated APE1 protein expression in CIS corresponded with reduced survival (p = 0.0243). Increased APE1 gene expression in stage T4a HNSCC was associated with reduced patient survival (p < 0.015). Increased PPARGC1A in invasive tumor correlated with reduced survival (p = 0.0281). Patients with lymph node invasion at diagnosis had significantly increased APE1 protein in the primary sites (p < 0.05). Patients with poorly differentiated invasive tumors had reduced PPARGC1A in CIS proximal to the invasive tumor and had elevated DCN and SOD3 in proximal benign tissue (p < 0.05). CONCLUSIONS: The expression of APE1, DCN, and SOD3 is a potential prognostic signature that identifies patients with worsened survival.

p300/CBP inhibition enhances the efficacy of programmed death-ligand 1 blockade treatment in prostate cancer.

Blockade of programmed death-ligand 1 (PD-L1) by therapeutic antibodies has shown to be a promising strategy in cancer therapy, yet clinical response in many types of cancer, including prostate cancer (PCa), is limited. Tumor cells secrete PD-L1 through exosomes or splice variants, which has been described as a new mechanism for the resistance to PD-L1 blockade therapy in multiple cancers, including PCa. This suggests that cutting off the secretion or expression of PD-L1 might improve the response rate of PD-L1 blockade therapy in PCa treatment. Here we report that p300/CBP inhibition by a small molecule p300/CBP inhibitor dramatically enhanced the efficacy of PD-L1 blockade treatment in a syngeneic model of PCa by blocking both the intrinsic and IFN-γ-induced PD-L1 expression. Mechanistically, p300/CBP could be recruited to the promoter of CD274 (encoding PD-L1) by the transcription factor IRF-1, which induced the acetylation of Histone H3 at CD274 promoter followed by the transcription of CD274. A485, a p300/CBP inhibitor, abrogated this process and cut off the secretion of exosomal PD-L1 by blocking the transcription of CD274, which combined with the anti-PD-L1 antibody to reactivate T cells function for tumor attack. This finding reports a new mechanism of how cancer cells regulate PD-L1 expression through epigenetic factors and provides a novel therapeutic approach to enhance the efficacy of immune checkpoint inhibitors treatment.

BRD4 modulates vulnerability of triple-negative breast cancer to targeting of integrin-dependent signaling pathways.

PURPOSE: Stemming from a myriad of genetic and epigenetic alterations, triple-negative breast cancer (TNBC) is tied to poor clinical outcomes and aspires for individualized therapies. Here we investigated the therapeutic potential of co-inhibiting integrin-dependent signaling pathway and BRD4, a transcriptional and epigenetic mediator, for TNBC. METHODS: Two independent patient cohorts were subjected to bioinformatic and IHC examination for clinical association of candidate cancer drivers. The efficacy and biological bases for co-targeting these drivers were interrogated using cancer cell lines, a protein kinase array, chemical inhibitors, RNAi/CRISPR/Cas9 approaches, and a 4 T1-Balb/c xenograft model. RESULTS: We found that amplification of the chromosome 8q24 region occurred in nearly 20% of TNBC tumors, and that it coincided with co-upregulation or amplification of c-Myc and FAK, a key effector of integrin-dependent signaling. This co-upregulation at the mRNA or protein level correlated with a poor patient survival (p < 0.0109 or p < 0.0402, respectively). Furthermore, we found that 14 TNBC cell lines exhibited high vulnerabilities to the combination of JQ1 and VS-6063, potent pharmacological antagonists of the BRD4/c-Myc and integrin/FAK-dependent pathways, respectively. We also observed a cooperative inhibitory effect of JQ1 and VS-6063 on tumor growth and infiltration of Ly6G+ myeloid-derived suppressor cells in vivo. Finally, we found that JQ1 and VS-6063 cooperatively induced apoptotic cell death by altering XIAP, Bcl2/Bcl-xl and Bim levels, impairing c-Src/p130Cas-, PI3K/Akt- and RelA-associated signaling, and were linked to EMT-inducing transcription factor Snail- and Slug-dependent regulation. CONCLUSION: Based on our results, we conclude that the BRD4/c-Myc- and integrin/FAK-dependent pathways act in concert to promote breast cancer cell survival and poor clinical outcomes. As such, they represent promising targets for a synthetic lethal-type of therapy against TNBC.

Chronic wasting disease prions in elk antler velvet.

Chronic wasting disease (CWD) is a contagious, fatal prion disease of deer and elk that continues to emerge in new locations. To explore the means by which prions are transmitted with high efficiency among cervids, we examined prion infectivity in the apical skin layer covering the growing antler (antler velvet) by using CWD-susceptible transgenic mice and protein misfolding cyclic amplification. Our finding of prions in antler velvet of CWD-affected elk suggests that this tissue may play a role in disease transmission among cervids. Humans who consume antler velvet as a nutritional supplement are at risk for exposure to prions. The fact that CWD prion incubation times in transgenic mice expressing elk prion protein are consistently more rapid raises the possibility that residue 226, the sole primary structural difference between deer and elk prion protein, may be a major determinant of CWD pathogenesis.

Characterization of Squamous Cell Lung Cancers from Appalachian Kentucky.

BACKGROUND: Lung cancer is the leading cause of cancer mortality in the United States (U.S.). Squamous cell carcinoma (SQCC) represents 22.6% of all lung cancers nationally, and 26.4% in Appalachian Kentucky (AppKY), where death from lung cancer is exceptionally high. The Cancer Genome Atlas (TCGA) characterized genetic alterations in lung SQCC, but this cohort did not focus on AppKY residents. METHODS: Whole-exome sequencing was performed on tumor and normal DNA samples from 51 lung SQCC subjects from AppKY. Somatic genomic alterations were compared between the AppKY and TCGA SQCC cohorts. RESULTS: From this AppKY cohort, we identified an average of 237 nonsilent mutations per patient and, in comparison with TCGA, we found that PCMTD1 (18%) and IDH1 (12%) were more commonly altered in AppKY versus TCGA. Using IDH1 as a starting point, we identified a mutually exclusive mutational pattern (IDH1, KDM6A, KDM4E, JMJD1C) involving functionally related genes. We also found actionable mutations (10%) and/or intermediate or high-tumor mutation burden (65%), indicating potential therapeutic targets in 65% of subjects. CONCLUSIONS: This study has identified an increased percentage of IDH1 and PCMTD1 mutations in SQCC arising in the AppKY residents versus TCGA, with population-specific implications for the personalized treatment of this disease. IMPACT: Our study is the first report to characterize genomic alterations in lung SQCC from AppKY. These findings suggest population differences in the genetics of lung SQCC between AppKY and U.S. populations, highlighting the importance of the relevant population when developing personalized treatment approaches for this disease.

Neurotensin Receptor 3/Sortilin Contributes to Tumorigenesis of Neuroendocrine Tumors Through Augmentation of Cell Adhesion and Migration.

Neurotensin (NTS), a 13-amino acid peptide which is distributed predominantly along gastrointestinal tract, has multiple physiologic and pathologic functions, and its effects are mediated by three distinct NTS receptors (NTSRs). Overexpression and activation of NTS signaling components, especially NTS and/or NTSR1, are closely linked with cancer progression and metastasis in various types of cancers including neuroendocrine tumors (NETs). Although deregulation of NTSR3/sortilin has been implicated in a variety of human diseases, the expression and role of NTSR3/sortilin in NETs have not been elucidated. In this study, we investigated the expression and oncogenic effect of NTSR3/sortilin in NETs. Increased protein levels of NTSR3/sortilin were noted in the majority of human clinical NETs (n=21) by immunohistochemical analyses compared with normal tissues (n=12). Expression of NTS and NTSR3/sortilin was also noted in all tested NET cell lines. In addition, small interfering RNA-mediated knockdown of NTSR3/sortilin decreased cell number without alteration of cell cycle progression and apoptosis induction in NET cell lines BON and QGP-1. Moreover, silencing of NTSR3/sortilin significantly suppressed cell adhesion and cell migration with inhibition of focal adhesion kinase and Src phosphorylation in the NET cells. Our results demonstrate increased expression of NTSR3/sortilin in NET patient tissues and a critical role of NTSR3/sortilin on NET cell adhesion and migration suggesting that NTSR3/sortilin contributes to NET tumorigenesis.

Downregulation of SREBP inhibits tumor growth and initiation by altering cellular metabolism in colon cancer.

Sterol regulatory element-binding proteins (SREBPs) belong to a family of transcription factors that regulate the expression of genes required for the synthesis of fatty acids and cholesterol. Three SREBP isoforms, SREBP1a, SREBP1c, and SREBP2, have been identified in mammalian cells. SREBP1a and SREBP1c are derived from a single gene through the use of alternative transcription start sites. Here we investigated the role of SREBP-mediated lipogenesis in regulating tumor growth and initiation in colon cancer. Knockdown of either SREBP1 or SREBP2 decreased levels of fatty acids as a result of decreased expression of SREBP target genes required for lipid biosynthesis in colon cancer cells. Bioenergetic analysis revealed that silencing SREBP1 or SREBP2 expression reduced the mitochondrial respiration, glycolysis, as well as fatty acid oxidation indicating an alteration in cellular metabolism. Consequently, the rate of cell proliferation and the ability of cancer cells to form tumor spheroids in suspension culture were significantly decreased. Similar results were obtained in colon cancer cells in which the proteolytic activation of SREBP was blocked. Importantly, knockdown of either SREBP1 or SREBP2 inhibited xenograft tumor growth in vivo and decreased the expression of genes associated with cancer stem cells. Taken together, our findings establish the molecular basis of SREBP-dependent metabolic regulation and provide a rationale for targeting lipid biosynthesis as a promising approach in colon cancer treatment.

Colorectal cancer lung metastasis treatment with polymer-drug nanoparticles.

Colorectal cancer (CRC) is the second leading cause of cancer deaths in the United States; the predominant cause for mortality is metastasis to distant organs (e.g., lung). A major problem limiting the success of chemotherapy in metastatic CRC is the inability to target tumor tissues selectively and avoid severe side effects to normal tissues and organs. Here, we demonstrate polymeric nanoparticles (PNPs) entrapping chemotherapeutic agents provide a new therapeutic option for treating CRC that has metastasized to the lung. PNPs assembled from FDA approved biocompatible block copolymer accumulated predominantly in lung tissue. PNPs showed negligible accumulation in liver, spleen and kidneys, which was confirmed by fluorescent nanoparticle imaging and analysis of PI3K inhibition in the organs. PNPs entrapping PI3K inhibitors (i.e., wortmannin and PX866) suppressed CRC lung metastasis growth, and SN-38-loaded PNPs completely eliminated CRC lung metastasis. Our results demonstrate that polymer-drug nanoparticles offer a new approach to reduce toxicity of cancer therapy and has the potential to improve outcomes for patients with lung metastasis.