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Parallel slopes indicate identical response to Stattic in PTPRT WT and KO mice. Vertical distance indicates improved outcome of Stattic-treated mice compared to vehicle-treated.

Supplemental Figure Legend.

Head and neck squamous cell carcinoma (HNSCC) is a frequently fatal disease due, in large part, to a high rate of second primary tumor (SPT) formation. The 4-nitroquinoline 1-oxide (4-NQO) mouse model of oral carcinogenesis provides a robust system in which to study chemopreventive agents in the context of chemically induced HNSCC tumors. STAT3 is a potent oncogene that is hyperactivated by tyrosine phosphorylation early in HNSCC carcinogenesis and is a rational therapeutic target. We recently reported that loss-of-function of the STAT3 phosphatase PTPRT promotes STAT3 activation in HNSCC tumors and preclinical models and may serve as a predictive biomarker of response to STAT3 inhibitors, including the small-molecule Stattic. We therefore investigated the hypothesis that Ptprt-knockout (KO) mice would be more susceptible to 4-NQO–induced oral carcinogenesis and more sensitive to Stattic-mediated chemoprevention compared with wild-type (WT) mice. Herein, we demonstrate that Ptprt WT and KO mice develop similar spectra of HNSCC disease severity upon 12 weeks of 4-NQO administration, with no apparent effect of Ptprt genotype on carcinogenesis or treatment outcome. Targeting of STAT3 with Stattic resulted in a chemopreventive effect against 4-NQO–induced oral cancer (P = 0.0402). While these results do not support a central role for PTPRT in 4-NQO–induced HNSCC carcinogenesis, further investigation of STAT3 as a chemoprevention target in this cancer is warranted. Cancer Prev Res; 9(8); 657–63. ©2016 AACR.

We previously identified that human epidermal growth factor receptor 3 (HER3, also known as ERBB3) is a key mediator in liver endothelial cell (EC) promoting colorectal cancer growth and chemoresistance, and suggested HER3-targeted therapy as a strategy for treating patients with metastatic colorectal cancer in the liver. Meanwhile, KRAS mutations occur in 40%–50% of metastatic colorectal cancer and render colorectal cancer resistant to therapies targeting the other HER family protein epidermal growth factor receptor (EGFR). It is necessary to elucidate the roles of KRAS mutation status in HER3-mediated cell survival and colorectal cancer response to HER3 inhibition. In the present study, we used primary ECs isolated from non-neoplastic liver tissues to recapitulate the liver EC microenvironment. We demonstrated that liver EC-secreted factors activated colorectal cancer-associated HER3, and increased colorectal cancer cell survival in vitro and promoted colorectal cancer patient-derived xenograft tumor growth in vivo. Moreover, we determined that blocking HER3, either by siRNA knockdown or the humanized antibody seribantumab, blocked EC-induced colorectal cancer survival in vitro in both KRAS wild-type and mutant colorectal cancer cells, and the HER3 antibody seribantumab significantly decreased colorectal cancer tumor growth and sensitized tumors to chemotherapy in an orthotopic xenograft model with colorectal cancer tumors developed in the liver. In summary, our findings demonstrated that blocking HER3 had significant effects on attenuating liver EC-induced colorectal cancer cell survival independent of the KRAS mutation status.Implications:This body of work highlighted a potential strategy of using HER3 antibodies in combination with standard chemotherapy agents for treating patients with either KRAS wild-type or KRAS mutant metastatic colorectal cancer.

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Supplementary Figure from Liver Endothelium Promotes HER3-Mediated Cell Survival in Colorectal Cancer with Wild-Type and Mutant KRAS

Hyperphosphorylation at the Y705 residue of signal transducer and activator of transcription 3 (STAT3) is implicated in tumorigenesis of leukemia and some solid tumors. However, its role in the development of colorectal cancer is not well defined. To rigorously test the impact of this phosphorylation on colorectal tumorigenesis, we engineered a STAT3 Y705F knock-in to interrupt STAT3 activity in HCT116 and RKO colorectal cancer cells. These STAT3 Y705F mutant cells fail to respond to cytokine stimulation and grow slower than parental cells. These mutant cells are also greatly diminished in their abilities to form colonies in culture, to exhibit anchorage-independent growth in soft agar, and to grow as xenografts in nude mice. These observations strongly support the premise that STAT3 Y705 phosphorylation is crucial in colorectal tumorigenesis. Although it is generally believed that STAT3 functions as a transcription factor, recent studies indicate that transcription-independent functions of STAT3 also play an important role in tumorigenesis. We show here that wild-type STAT3, but not STAT3 Y705F mutant protein, associates with phospholipase Cγ1 (PLCγ1). PLCγ1 is a central signal transducer of growth factor and cytokine signaling pathways that are involved in tumorigenesis. In STAT3 Y705F mutant colorectal cancer cells, PLCγ1 activity is reduced. Moreover, overexpression of a constitutively active form of PLCγ1 rescues the transformation defect of STAT3 Y705F mutant cells. In aggregate, our study identifies previously unknown cross-talk between STAT3 and the PLCγ signaling pathways that may play a critical role in colorectal tumorigenesis. Mol Cancer Res; 9(10); 1418–28. ©2011 AACR.

Supplementary proteomics data

Supplementary Figures 1-7. Supplementary Figure 1.Cell-cycle profiles of HEK293T cells following treatment with Wnt3a. Supplementary Figure 2. Protein lysate samples used in the immunoprecipitation or immunoblots analyses were treated with Nuclease. Supplementary Figure 3. Dnmt1 (native antibody) immuno-precipitates β-catenin in parent HCT116 cells. Supplementary Figure 4. DNMT1 protein is stabilized by treatment with Wnt3a in HCT116 but not in CTNNB1KO-HCT116 cells. Supplementary Figure 5. Degradation profiles for β-catenin and Dnmt1 in HCT116, DNMT1KO-HCT116 or CTNNB1KO-HCT116 cells following cycloheximide treatment. Supplementary Figure 6. Abundance of β-catenin and Dnmt1 in DNMT1KO-HCT116 (A) or CTNNB1KO-HCT116 (B) cells treated with MG-132 proteasome inhibitor. Supplementary Figure 7. RT-PCR analysis of H19 expression in HCT116 and CTNNB1KO-HCT116 cells shows increase H19 transcript levels in the KO cells.

Supplementary Figures 1-6 and Tables 1-3. Figure S1. PIK3CA mutant cells are more sensitive to a glutaminase inhibitor CB-839 than their WT counterparts. Figure S2. CB-839 enhances 5-FU tumor inhibitory effect in PIK3CA mutant CRC. Figure S3. Genes and pathways that are up-regulated in PIK3CA mutant cells after glutamine deprivation. Figure S4. Characterization of Nrf2 and its targets in CRC cells. Figure S5. CB-839 and 5-FU combinational treatment induces more DNA damage. Figure S6. Phase I clinical trial. Table S1: Patient Baseline Characteristics. Table S2. Patient information. Table S3. Treatment Related Adverse Events (all grade 3/4 AEs and grade 1/2 AEs seen in {greater than or equal to} 10% of patients).

PIK3CA encodes the p110α catalytic subunit of PI3K and is frequently mutated in human cancers, including ∼30% of colorectal cancer. Oncogenic mutations in PIK3CA render colorectal cancers more dependent on glutamine. Here we report that the glutaminase inhibitor CB-839 preferentially inhibits xenograft growth of PIK3CA-mutant, but not wild-type (WT), colorectal cancers. Moreover, the combination of CB-839 and 5-fluorouracil (5-FU) induces PIK3CA-mutant tumor regression in xenograft models. CB-839 treatment increased reactive oxygen species and caused nuclear translocation of Nrf2, which in turn upregulated mRNA expression of uridine phosphorylase 1 (UPP1). UPP1 facilitated the conversion of 5-FU to its active compound, thereby enhancing the inhibition of thymidylate synthase. Consistently, knockout of UPP1 abrogated the tumor inhibitory effect of combined CB-839 and 5-FU administration. A phase I clinical trial showed that the combination of CB-839 and capecitabine, a prodrug of 5-FU, was well tolerated at biologically-active doses. Although not designed to test efficacy, an exploratory analysis of the phase I data showed a trend that PIK3CA-mutant patients with colorectal cancer might derive greater benefit from this treatment strategy as compared with PIK3CA WT patients with colorectal cancer. These results effectively demonstrate that targeting glutamine metabolism may be an effective approach for treating patients with PIK3CA-mutant colorectal cancers and warrants further clinical evaluation.Significance:Preclinical and clinical trial data suggest that the combination of CB-839 with capecitabine could serve as an effective treatment for PIK3CA-mutant colorectal cancers.

Supplementary Figure 1 from Ugene, a Newly Identified Protein That Is Commonly Overexpressed in Cancer and Binds Uracil DNA Glycosylase

Supplementary Table 1, Figure Legends 1-4 from Ugene, a Newly Identified Protein That Is Commonly Overexpressed in Cancer and Binds Uracil DNA Glycosylase

microRNAs (miRNA) are small noncoding RNAs that participate in diverse biological processes by suppressing target gene expression. Altered expression of miR-21 has been reported in cancer. To gain insights into its potential role in tumorigenesis, we generated miR-21 knockout colon cancer cells through gene targeting. Unbiased microarray analysis combined with bioinformatics identified cell cycle regulator Cdc25A as a miR-21 target. miR-21 suppressed Cdc25A expression through a defined sequence in its 3′-untranslated region. We found that miR-21 is induced by serum starvation and DNA damage, negatively regulates G1-S transition, and participates in DNA damage–induced G2-M checkpoint through down-regulation of Cdc25A. In contrast, miR-21 deficiency did not affect apoptosis induced by a variety of commonly used anticancer agents or cell proliferation under normal cell culture conditions. Furthermore, miR-21 was found to be underexpressed in a subset of Cdc25A-overexpressing colon cancers. Our data show a role of miR-21 in modulating cell cycle progression following stress, providing a novel mechanism of Cdc25A regulation and a potential explanation of miR-21 in tumorigenesis. [Cancer Res 2009;69(20):8157–65]

Supplementary Figure 2 from Ugene, a Newly Identified Protein That Is Commonly Overexpressed in Cancer and Binds Uracil DNA Glycosylase

Supplementary Figure 3 from Ugene, a Newly Identified Protein That Is Commonly Overexpressed in Cancer and Binds Uracil DNA Glycosylase

Supplementary Methods, Figures 1-6. Tables 1-5 from microRNA-21 Negatively Regulates Cdc25A and Cell Cycle Progression in Colon Cancer Cells

Supplementary Figure 4 from Ugene, a Newly Identified Protein That Is Commonly Overexpressed in Cancer and Binds Uracil DNA Glycosylase

Background: 25% of patients diagnosed with colorectal cancer (CRC) have liver metastasis at presentation, and ~80% of all metastatic CRC are developed in the liver. We previously reported that liver endothelial cells (ECs), a key component of the liver microenvironment, secrete LRG1 to promote CRC growth via activating human epidermal growth factor receptor (ERbB3, also known as HER3). However, we found that LRG1-induced HER3 activation is distinct from the canonical neuregulin 1 (NRG1)-induced HER3 pathway. The present study further validated LRG1 as a new HER3 ligand for promoting mCRC growth and elucidated the novel downstream signaling pathway induced by LRG1-HER3. Methods: We first measured the binding affinity between HER3 and LRG1 by Biolayer interferometry (BLI). We then used in vitro and in vivo xenograft approaches to determine the effect of LRG1 monoclonal antibody (15C4) on HER3 activation and CRC growth. To further determine the role of LRG1 in promoting CRC growth in the liver, we used murine CRC cells in a syngeneic orthotropic liver injection model to establish CRC allografts in the liver of LRG1−/− mice with systemic LRG1 knockout and wild-type siblings (LRG1+/+). We also performed unbiased phospho-MS analysis and subsequent validations to determine the downstream signaling pathway activated by LRG1-HER3. Results: We identified that LRG1 binds to HER3 with the affinity at ~100nM. The LRG1 antibody 15C4 completely attenuated LRG1-induced HER3 activation and in vitro and xenograft growth in vivo. Moreover, LRG1−/− mice with CRC allografts in the liver had 2 times longer overall survival than tumor-bearing LRG1+/+ mice. Lastly, unbiased -omics analysis identified eIF4-protein synthesis is significantly activated by LRG1. With target-specific inhibitors, we further determined that LRG1-HER3 activates the PI3K-PDK1-RSK1/3-eIF4 axis independent of AKT. Conclusions: We identified LRG1 as a novel HER3 ligand and demonstrated that the liver microenvironment-derived LRG1 plays a key oncogenic role in mCRC, by activating a novel RSK-eIF4 survival pathway. Our findings highlighted the potential of blocking LRG1-HER3 and involved downstream pathways for treating patients with mCRC. Citation Format: Moeez Ghani Rathore, Michelle Wright, Wei Huang, Derek Taylor, Yamu Li, Jordan Winter, Zhenghe Wang, John Greenwood, Stephen Moss, Rui Wang. Liver endothelium secreted LRG1 promotes metastatic colorectal cancer growth through the HER3/RSK/EIF4B AXIS. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3636.

PIK3CA encodes the p110α catalytic subunit of PI3K and is frequently mutated in human cancers, including ∼30% of colorectal cancer. Oncogenic mutations in PIK3CA render colorectal cancers more dependent on glutamine. Here we report that the glutaminase inhibitor CB-839 preferentially inhibits xenograft growth of PIK3CA-mutant, but not wild-type (WT), colorectal cancers. Moreover, the combination of CB-839 and 5-fluorouracil (5-FU) induces PIK3CA-mutant tumor regression in xenograft models. CB-839 treatment increased reactive oxygen species and caused nuclear translocation of Nrf2, which in turn upregulated mRNA expression of uridine phosphorylase 1 (UPP1). UPP1 facilitated the conversion of 5-FU to its active compound, thereby enhancing the inhibition of thymidylate synthase. Consistently, knockout of UPP1 abrogated the tumor inhibitory effect of combined CB-839 and 5-FU administration. A phase I clinical trial showed that the combination of CB-839 and capecitabine, a prodrug of 5-FU, was well tolerated at biologically-active doses. Although not designed to test efficacy, an exploratory analysis of the phase I data showed a trend that PIK3CA-mutant patients with colorectal cancer might derive greater benefit from this treatment strategy as compared with PIK3CA WT patients with colorectal cancer. These results effectively demonstrate that targeting glutamine metabolism may be an effective approach for treating patients with PIK3CA-mutant colorectal cancers and warrants further clinical evaluation. Significance: Preclinical and clinical trial data suggest that the combination of CB-839 with capecitabine could serve as an effective treatment for PIK3CA-mutant colorectal cancers.

Background: Liver is the most common site of developing distant metastasis in colorectal cancer (CRC). Patients with metastatic CRC (mCRC) have a 5-year survival rate at 14%. We previously showed that liver endothelial cells (EC), a key component of the liver microenvironment, secrete soluble factors to promote CRC growth and chemoresistance via activating human epidermal growth factor receptor (ERBB3, also known as HER3). However, we found that the ECs activated HER3 by a previously unknown mechanism that is independent of the established HER3 ligand neuregulins. Identifying a new HER3 ligand will potentially give rise to novel therapeutic target for treating patients with mCRC. Methods: We first fractionated conditioned medium (CM) from liver ECs by fast protein liquid chromatography. The specific fractions that activated HER3 and AKT in CRC cells were subjected to mass spectrometry (MS) for protein identification. In parallel, we used a His-tagged HER3 Extracellular domain (ECD) and pulled down EC-secreted factors that directly bound to HER3 and then subjected to protein identification by MS. Candidate proteins identified in both MS analyses were subjected for further validations by siRNA or immunoprecipitation depletion from EC CM to determine their roles in HER3 activation and CRC growth. Results: We identified a specific fraction of liver EC CM increased phosphorylation of HER3 and AKT in CRC cells (determined by Western blotting). Meanwhile, the HER3-ECD affinity binding assay showed that HER3 ECD-depleted EC CM could no longer activate HER3 or promote growth, and the soluble factor(s) eluted from HER3-ECD increased phosphorylation of HER3 and AKT, and promoted growth in CRC cells. Results from both MS analyses revealed that LRG1 is a potential ligand that binds to and activate HER3 in CRC cells. We depleted LRG1 from EC CM, either by siRNA knockdown LRG1 in ECs or immunoprecipitation, and found that LRG1-depleted EC CM could no longer activate HER3 and AKT in CRC cells, and LRG1-depleted EC CM failed to promote growth of CRC cell in vitro and CRC xenografts in vivo. Conclusions: We identified LRG1 as a new HER3 ligand and demonstrated that liver EC-secreted LRG1 mediates EC paracrine effects on activating HER3 and promoting CRC cell growth. Our findings suggest an oncogenic role of EC-secreted LRG1 in the surrounding liver microenvironment of mCRC, and highlighted a potential of blocking LRG1 with monoclonal antibodies for treating patients with mCRC. Citation Format: Moeez Ghani Rathore, Wei Zhang, Michel'le Wright, Jordan Winter, Yamu Li, Zhenghe Wang, Rui Wang. Liver endothelium secreted LRG1 is a novel ligand of HER3 to promote metastatic colorectal cancer growth [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3177.

Head and neck squamous cell carcinoma (HNSCC) is a frequently fatal disease due, in large part, to a high rate of second primary tumor (SPT) formation. The 4-nitroquinoline 1-oxide (4-NQO) mouse model of oral carcinogenesis provides a robust system in which to study chemopreventive agents in the context of chemically induced HNSCC tumors. STAT3 is a potent oncogene that is hyperactivated by tyrosine phosphorylation early in HNSCC carcinogenesis and is a rational therapeutic target. We recently reported that loss-of-function of the STAT3 phosphatase PTPRT promotes STAT3 activation in HNSCC tumors and preclinical models and may serve as a predictive biomarker of response to STAT3 inhibitors, including the small-molecule Stattic. We therefore investigated the hypothesis that Ptprt-knockout (KO) mice would be more susceptible to 4-NQO–induced oral carcinogenesis and more sensitive to Stattic-mediated chemoprevention compared with wild-type (WT) mice. Herein, we demonstrate that Ptprt WT and KO mice develop similar spectra of HNSCC disease severity upon 12 weeks of 4-NQO administration, with no apparent effect of Ptprt genotype on carcinogenesis or treatment outcome. Targeting of STAT3 with Stattic resulted in a chemopreventive effect against 4-NQO–induced oral cancer (P = 0.0402). While these results do not support a central role for PTPRT in 4-NQO–induced HNSCC carcinogenesis, further investigation of STAT3 as a chemoprevention target in this cancer is warranted. Cancer Prev Res; 9(8); 657–63. ©2016 AACR.

Department of Genetics & Genome Sciences and Case Comprehensive Cancer Center, Case Western Reserve University, 10900 Euclid Avenue, Cleveland, Ohio 44106, USA. In addition to phosphorylation, tyrosine residues in proteins can have nitration at the 3-carbon position on the phenol ring (Y-NO2). Protein tyrosine nitration occurs under both physiological and pathologic conditions. However, enzymes that add or remove this protein modification remain to be identified. Protein tyrosine phosphatase receptor T (PTPRT) is one of the twelve receptor protein tyrosine phosphatases (RPTPs) that have two catalytic PTP domains in their intracellular parts. While the membrane proximal PTP domains (D1) are protein tyrosine phosphatases, it has been thought that the C-terminal PTP domains (D2) are pseudo-phosphatase that lack enzymatic activity. Here we report that the pseudo-phosphatase domain (D2) of PTPRT is a denitrase that removes nitro-groups from tyrosine residues in paxillin. PTPRT normally functions as a tumor suppressor and is frequently mutated in a variety of human cancers including colorectal cancer. Interestingly, a fifth of tumor-derived mutations of PTPRT are located in the D2 pseudo-PTP domain. We demonstrate that some of the tumor-derived mutations located in the pseudo-phosphatase domain impair the denitrase activity. Moreover, PTPRT mutant mice that inactivate the denitrase activity are susceptible to carcinogen-induced colon tumor formation. Our study uncovers a novel enzyme that functions as a tumor suppressor. Citation Format: Yiqing Zhao, Zhenghe Wang. PTPRT pseudo-phosphatase domain is a denitrase that contributes to its tumor suppressor function [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2379.

Background: Colorectal cancer is the second leading cause of cancer death among adult Americans. Tumor stage still remains the clinical standard for determining prognosis of colon cancer patients and for selecting individuals for treatment with adjuvant chemotherapy. Genes induced in colon cancer provide novel candidate biomarkers of tumor phenotype and aggressiveness. The goal of this study was to identify genes whose expression is dramatically up-regulated in colon neoplasia even at the early stages of the disease, and with the potential to be new prognostic markers of patient outcome and/or targets for new therapies. Methods: We used expression microarrays, real-time PCR, Western blot, and immunohistochemistry to identify CEMIP (originally named KIAA1199/CCSP1) induction in colon cancer, and characterized the biological properties of the corresponding protein in cell-line and mouse xenografts. Sandwich ELISA was developed to determine CEMIP plasma levels in patients with colon cancer. Prognostic importance of gene induction was demonstrated by real-time PCR measurement of gene expression in colon cancer cases of known clinical outcome. Results: We originally identified CEMIP as a novel transcript that is induced an average of 54-fold in colon cancer, with a similar increase in protein level. We find that CEMIP is a secreted protein and that plasma levels of CEMIP in colon cancer patients is increased compared to normal subjects (P = 0.05). Knocking out CEMIP in a human colon cancer cell line markedly reduced growth of tumor xenografts implanted in athymic mice. Tumors that did grow had increased deposition of hyaluronan, linking CEMIP participation in hyaluronan degradation to the modulation of tumor phenotype. Human stage III colon cancer cases with greater than average increased tumor CEMIP expression had a median survival time of 37 months, versus greater than 140 months for colon cancer cases with below average CEMIP expression (P = 0.004). Similarly, among combined stage II plus III colon cancer cases, median survival decreased by 92 months for CEMIP high versus low expressing tumors (P = 0.0003). Conclusions: CEMIP is highly expressed in colon neoplasia and is a novel member of the colon cancer secreted proteome making it a candidate serological marker of early human colon neoplasia. CEMIP facilitates tumor growth, and high CEMIP correlates with poor outcome in stage III and in stages II plus III combined cohorts. CEMIP may have utility as both a prognostic marker of colon cancer outcome, and as a potential therapeutic target. Citation Format: Stephen P. Fink, Lois Myeroff, Revital Kariv, Petra Platzer, Baozhong Xin, Debra Mikkola, Earl Lawrence, Nathan Morris, Arman Nosrati, James Willson, Joseph Willis, Martina Veigl, Jill Barnholtz-Sloan, Zhenghe Wang, Sanford Markowitz. CEMIP, a secreted protein highly induced in colon cancer and associated with poor patient survival. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3126.

Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. PIK3CA, which encodes the p110 alpha catalytic subunit of phosphatidylinositol 3-kinase, is the most frequently mutated oncogene in human cancers. However, whether PIK3CA mutations reprogram cancer metabolism is an important unaddressed question. Using isogenic cell lines expressing either wild-type (WT) or oncogenic mutant allele of PIK3CA, we demonstrated that colorectal cancer cells harboring PIK3CA mutations are more dependent on glutamine to grow. In contrast, the isogenic PIK3CA WT and mutant cell lines did not show differential sensitivity to glucose deprivation. Through gene expression analyses, we showed that glutamate pyruvate transaminase 2 (GPT2) is up-regulated in the colorectal cancer cell lines with PIK3CA mutations compared to the isogenic cell lines expressing WT PIK3CA. We demonstrated that induction of GPT2 by mutant p110 alpha is necessary and sufficient to render colorectal cancer cells dependent on glutamine. Moreover, aminooxyacetate, which inhibits enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumor growth of colorectal cancers with PIK3CA mutations, but not colorectal cancers with WT PIK3CA. Thus our data suggest that targeting glutamine metabolism may be an effective approach to treat colorectal cancer patients harboring PIK3CA mutations. Mutant p110 alpha up-regulates GPT2 gene expression through an AKT-independent PDK1-RSK2-ATF4 signaling axis. We showed that ATF4 is a transcription factor that activates GPT2 gene expression. We further demonstrated that mutant p110 alpha activates RSK2 kinase through PDK1. Activated RSK2 then phosphorylates ATF4 at the serine residue 245, which in turn recruits deubiquitinase USP8 and protects ATF4 from ubiquitin-mediated degradation. Lastly, using [13C5-]glutamine isotope-tracing technology, we showed that PIK3CA mutant colorectal cancer cells convert more glutamine to alpha-keto-glutarate to replenish the tricarboxylic acid cycle to generate ATP. Together, our data establish oncogenic PIK3CA mutations as a cause of glutamine addiction in colorectal cancers. Citation Format: Zhenghe Wang. Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B03.

Glutamine addiction is a major metabolic reprogramming event that occurs in cancer cells. Many tumors exhibit oncogene-dependent addiction to glutamine. PIK3CA, which encodes the p110α catalytic subunit of phosphatidylinositol 3-kinase α, is the most frequently mutated oncogene in human cancers. However, whether PIK3CA mutations reprogram cancer metabolism is an important unaddressed question. Here we show that oncogenic PIK3CA mutations reprogram glutamine metabolism by up-regulating glutamate pyruvate transaminase 2 (GPT2) in colorectal cancer (CRC) cells, thereby rendering them addicted to glutamine. We demonstrated that induction of GPT2 by mutant p110α is necessary and sufficient to render CRC cells addicted to glutamine. Moreover, aminooxyacetate, which inhibits enzymatic activity of aminotransferases including GPT2, suppresses xenograft tumor growth of CRCs with PIK3CA mutations, but not CRCs with WT PIK3CA. Thus our data suggest that targeting glutamine metabolism may be an effective approach to treat CRC patients harboring PIK3CA mutations. Mutant p110α up-regulates GPT2 gene expression through an AKT-independent PDK1-RSK2-ATF4 signaling axis. We showed that ATF4 is a transcription factor that activates GPT2 gene expression. We further demonstrated that mutant p110α activates RSK2 kinase through PDK1. Activated RSK2 then phosphorylates ATF4 at the serine residue 245, which in turn recruits deubiquitinase USP8 and protects ATF4 from ubiquitin-mediated degradation. Lastly, using [13C5-]glutamine isotope-tracing technology, we showed that PIK3CA mutant CRCs convert more glutamine to α-keto-glutarate to replenish the tricarboxylic acid (TCA) cycle to generate ATP. Together, our data establish oncogenic PIK3CA mutations as a cause of glutamine addiction in CRCs. Citation Format: Yujun Hao, Yardena Samuels, Qingling Li, Dawid Krokowski, Henri Brunengraber, Maria Hatzoglou, Guo-Fang Zhang, Bert Vogelstein, Zhenghe Wang. Oncogenic PIK3CA mutations reprogram glutamine metabolism in colorectal cancers. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1125. doi:10.1158/1538-7445.AM2015-1125

PIK3CA, which encodes the catalytic subunit of phosphoinositide 3-kinase PI3Kα (p110α), is frequently mutated in human cancers. PI3Kα consists of a catalytic subunit p110α and one of several regulatory subunits (a major one being p85α). The p110α subunit contains an N-terminal adaptor-binding domain (ABD), a Ras-binding domain (RBD), a C2 domain, a helical domain and a catalytic domain. In the basal state, the regulatory p85 subunit stabilizes the catalytic p110α subunit and inhibits its enzymatic activity. Upon growth factor stimulation, the SH2 domains of p85 bind to the phospho-tyrosine residues on the receptor protein kinases or adaptor proteins such as insulin receptor substrate 1 (IRS1), thereby activating the lipid kinase activity of PI3Kα. Activated PI3Kα converts phosphatidylinositol-4,5-bisphosphate (PIP2) to phosphatidylinositol-3,4,5-triphosphate (PIP3). The second messenger PIP3 then activates downstream AKT signaling. The majority of these mutations occur at two hot-spots located in the helical (E545K) and the kinase (H1047R) domains. Here, we report that p110α E545K mutant proteins, but not the wild-type and H1047R mutant proteins, directly associate with IRS1 and that this interaction does not require the p85 regulatory subunit of PI3Kα. Disruption of IRS1-p110α E545K specific interaction results in reduction of AKT phosphorylation and slower xenograft tumor growth of a colon cancer cell line harboring this mutation. Moreover, IRS1- p110α E545K interaction stabilizes p110α proteins and brings it cytoplasmic membrane. Our study establishes a new paradigm whereby a mutant protein exerts its oncogenic functions through rewiring an oncogenic signaling pathway. Moreover, we designed an 18 amino acid hydrocarbon-stapled peptide encompassing the p110α E545K mutation that disrupts IRS1-p110α E545K interaction. The stapled mutant peptide reduces AKT phosphorylation in cancer cell lines with a p110α E545K mutation, whereas it has no effect on those cancer cell lines harboring a p110α H1047R mutation. When injected into xenograft tumors, the stapled peptide specifically inhibits growth of tumors with a p110α E545K mutation. Therefore, our data suggest that interference of IRS1-p110α E545K interaction may be exploited for targeted therapy of cancer patients harboring this mutation. The discovery of frequent mutations of PIK3CA in human cancer provides a strong rationale for inhibition of mutated p110α activities for targeted cancer therapy. However, it has remained a challenge to develop p110α isoform-specific inhibitors. Our data suggest that disruption of the interactions between helical domain mutations of p110α and IRS1 may be exploited as a more accessible targeted therapy approach. Citation Format: Yujun Hao, Chao Wang, Weiping Zheng, David Sedwick, Sanford Markowitz, Rob Ewing, Lili Liu, Zhenghe Wang. Gain of direct interaction with IRS1 by the helical domain mutations of p110 alpha is crucial for their oncogenic functions. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5155. doi:10.1158/1538-7445.AM2013-5155

Protein tyrosine phosphatases (PTPs) are thought to be potentially important regulators in tumorigenesis as antagonists of protein tyrosine kinases (PTKs). Among them, Protein tyrosine non-receptor type 14 (PTPN14) has been shown to be mutated in both colorectal and breast cancers. However, little is known about the cellular signaling pathways it regulates. In order to determine whether PTPN14 has causative roles in tumorigenesis, we set out to identify substrates of PTPN14 and shed light on the mechanism why it is mutated in different tumor types. In this study, we report the identification of p130Cas, a scaffolding molecule, as a substrate of PTPN14 through a proteomic approach. We show that PTPN14 specifically dephosphorylates p130Cas at tyrosine 128 by shRNA knockdown and overexpression. We also demonstrate p130Cas is a direct substrate of PTPN14 by substrate trapping and in vitro phosphatase assays. We then mutate tyrosine 128 residue to phenylalanine in DLD1 and RKO, two different colorectal cell lines, to study the biological functions of this phosphosite. The mutant cells show reduced tumorigenicity based on colony formation and soft agar assays. However, the phenotypes diverge between the mutant cells from the two cell lines when we test the effect of the mutation on tumor growth in xenograft model. RKO Y128F mutant cells display significantly reduced tumor volumes while DLD1 Y128F mutant cells do not. In addition, RKO Y128F mutant cells are less invasive than parental cells in Matrigel but DLD1 Y128F mutant cells are surprisingly more invasive. We find that AKT is not fully activated in both mutant cells, which is likely the cause of the common phenotypes. However, phospho-ERK is up-regulated in DLD1 mutant cells possibly due to a compensatory mechanism but not in RKO mutant cells since ERK is already constitutively active in RKO cells, which explains the discrepancies in phenotypes mentioned above. Last, Src is shown to be the kinase of p130Cas Y128. When the phosphorylation of p130Cas Y128 is surveyed in six commonly used colorectal cancer cell lines, the phosphorylation levels are found to be correlated with the sensitivities to Src inhibitor. Thus, p130Cas Y128 phosphorylation can be utilized as a prognostic marker for Src inhibitors that are already in clinical trials. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 229. doi:1538-7445.AM2012-229