Pyruvate Kinase M1 Suppresses Development and Progression of Prostate Adenocarcinoma

SIGNIFICANCE

Differential expression of PKM1 and PKM2 impacts prostate tumorigenesis and suggests a potential therapeutic vulnerability in prostate cancer.

Abstract LB-333: PARP-1 supports HPV infection and HPV-associated head and neck cancer

Background:

As the incidence of human papillomavirus (HPV)-related head and neck squamous cell carcinoma (HNSCC) continues to rise, mechanistic knowledge of HPV16-driven HNSCC remains incomplete. HPV(+) and HPV(-) HNSCCs are molecularly distinct, with altered signaling pathways that have been characterized by proteomic technologies. We recently reported that poly(ADP-ribose)polymerase-1 (PARP-1) is overexpressed in HPV(+) compared to HPV(-) HNSCC. PARP-1 is a multi-functional protein with the ability to produce polymers of ADP-ribose attached to proteins and with major known roles in maintaining genomic integrity, DNA damage repair, transcription, DNA replication, and cell cycle regulation. However, PARP-1 functions in HPV infection and in head and neck cancer have not been fully uncovered. Here, we examine the role of PARP-1 in HPV infection, the interactions of HPV with cellular proteins, and the therapeutic implications of PARP-1 inhibition in HPV(+) HNSCC.

Methods:

PARP activity was assessed by immunoblotting for levels of poly(ADP-ribose) and by enzymatic PARP-1 ELISA. Expression of HPV genes was measured by RT-PCR. Murine kidney epithelial cells were established from PARP-1 wild-type and knockout mice, and the absence of PARP-1 expression was confirmed by RT-PCR and immunoblotting. Infection with HPV pseudovirus (PsV) containing a GFP expression plasmid was detected by L1 immunofluorescence staining and GFP detection. Survival studies were done in vitro and in vivo with PARP inhibitors veliparib and olaparib.

Results:

In addition to being overexpressed, we found that PARP-1 was highly enzymatically active in HPV(+) HNSCC as compared to HPV(-) tumors. HPV16 PsV and major capsid protein L1 activated PARP-1 in vitro and in cells. Depletion of PARP-1 and chemical PARP inhibition repressed HPV16 cellular entry, and infection of cells with HPV PsV increased sensitivity of HPV(-) cells to PARP inhibition.

Conclusions:

We identified a functional role of PARP-1 in initial HPV infection and in HPV-associated cancer. PARP-1 is activated by HPV major capsid protein L1, and HPV(+) HNSCCs maintain PARP-1 enzymatic activity. On top of its role in initial HPV infection, PARP-1 also appears to be important for survival of HPV-infected cells, as inhibition of PARP-1 sensitized cells to HPV PsV infection. These findings suggest that PARP inhibition may hold significant therapeutic potential in the treatment of HPV-associated HNSCC, with our work resulting in the initiation of a window clinical trial ongoing at the Yale Cancer Center.

Citation Format: Cassie Pan, Asel Biktasova, Michael Hajek, Andrew Sewell, Tejas Sathe, Gary Bellinger, Wendell Yarbrough, Natalia Issaeva. PARP-1 supports HPV infection and HPV-associated head and neck cancer [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 LB-333.

Selective antitumor activity of roscovitine in head and neck cancer

Radiation and chemotherapy that are commonly used to treat human cancers damage cellular DNA. DNA damage appears to be more toxic to cancer cells than normal cells, most likely due to deregulated checkpoint activation and/or deficiency in DNA repair pathways that are characteristics of many tumors. However, unwanted side effects arise as a result of DNA damage to normal cells during the treatment.

Here, we show that roscovitine, a cyclin-dependent kinase (CDK) inhibitor that inhibits CDK-1, CDK-2, CDK-5, CDK-7, and CDK-9 due to competitive binding to the ATP site on the kinases, causes significant DNA damage followed by p53-dependent cell death in human papilloma virus (HPV)-positive, but not in HPV-negative, head and neck cancer cells. Since HPV positivity was a molecular marker for increased sensitivity of cells to roscovitine, we reasoned that systemic roscovitine administration would not be toxic to healthy HPV-negative tissue. Indeed, low roscovitine doses significantly inhibited the growth of HPV-associated xenografted tumors in mice without causing any detectable side effects.

Given that inhibition of CDKs has been shown to inhibit replication of several viruses, we suggest that roscovitine treatment may represent a selective and safe targeted therapeutic option against HPV-positive head and neck cancer.

Demethylation Therapy as a Targeted Treatment for Human Papillomavirus-Associated Head and Neck Cancer

Purpose: DNA methylation in human papillomavirus-associated (HPV⁺) head and neck squamous cell carcinoma (HNSCC) may have importance for continuous expression of HPV oncogenes, tumor cell proliferation, and survival. Here, we determined activity of a global DNA-demethylating agent, 5-azacytidine (5-aza), against HPV⁺ HNSCC in preclinical models and explored it as a targeted therapy in a window trial enrolling patients with HPV⁺ HNSCC.Experimental Design: Sensitivity of HNSCC cells to 5-aza treatment was determined, and then 5-aza activity was tested in vivo using xenografted tumors in a mouse model. Finally, tumor samples from patients enrolled in a window clinical trial were analyzed to identify activity of 5-aza therapy in patients with HPV⁺ HNSCC.Results: Clinical trial and experimental data show that 5-aza induced growth inhibition and cell death in HPV⁺ HNSCC. 5-aza reduced expression of HPV genes, stabilized p53, and induced p53-dependent apoptosis in HNSCC cells and tumors. 5-aza repressed expression and activity of matrix metalloproteinases (MMP) in HPV⁺ HNSCC, activated IFN response in some HPV⁺ head and neck cancer cells, and inhibited the ability of HPV⁺ xenografted tumors to invade mouse blood vessels.Conclusions: 5-aza may provide effective therapy for HPV-associated HNSCC as an alternative or complement to standard cytotoxic therapy. Clin Cancer Res; 23(23); 7276-87. ©2017 AACR.

Pyruvate kinase isoform expression alters nucleotide synthesis to impact cell proliferation

Metabolic regulation influences cell proliferation. The influence of pyruvate kinase isoforms on tumor cells has been extensively studied, but whether PKM2 is required for normal cell proliferation is unknown. We examine how PKM2 deletion affects proliferation and metabolism in nontransformed, nonimmortalized PKM2-expressing primary cells. We find that deletion of PKM2 in primary cells results in PKM1 expression and proliferation arrest. PKM1 expression, rather than PKM2 loss, is responsible for this effect, and proliferation arrest cannot be explained by cell differentiation, senescence, death, changes in gene expression, or prevention of cell growth. Instead, PKM1 expression impairs nucleotide production and the ability to synthesize DNA and progress through the cell cycle. Nucleotide biosynthesis is limiting, as proliferation arrest is characterized by severe thymidine depletion, and supplying exogenous thymine rescues both nucleotide levels and cell proliferation. Thus, PKM1 expression promotes a metabolic state that is unable to support DNA synthesis.

Depletion of a putatively druggable class of phosphatidylinositol kinases inhibits growth of p53-null tumors

Here, we show that a subset of breast cancers express high levels of the type 2 phosphatidylinositol-5-phosphate 4-kinases α and/or β (PI5P4Kα and β) and provide evidence that these kinases are essential for growth in the absence of p53. Knocking down PI5P4Kα and β in a breast cancer cell line bearing an amplification of the gene encoding PI5P4K β and deficient for p53 impaired growth on plastic and in xenografts. This growth phenotype was accompanied by enhanced levels of reactive oxygen species (ROS) leading to senescence. Mice with homozygous deletion of both TP53 and PIP4K2B were not viable, indicating a synthetic lethality for loss of these two genes. Importantly however, PIP4K2A(-/-), PIP4K2B(+/-), and TP53(-/-) mice were viable and had a dramatic reduction in tumor formation compared to TP53(-/-) littermates. These results indicate that inhibitors of PI5P4Ks could be effective in preventing or treating cancers with mutations in TP53.

PKM2 isoform-specific deletion reveals a differential requirement for pyruvate kinase in tumor cells

The pyruvate kinase M2 isoform (PKM2) is expressed in cancer and plays a role in regulating anabolic metabolism. To determine whether PKM2 is required for tumor formation or growth, we generated mice with a conditional allele that abolishes PKM2 expression without disrupting PKM1 expression. PKM2 deletion accelerated mammary tumor formation in a Brca1-loss-driven model of breast cancer. PKM2 null tumors displayed heterogeneous PKM1 expression, with PKM1 found in nonproliferating tumor cells and no detectable pyruvate kinase expression in proliferating cells. This suggests that PKM2 is not necessary for tumor cell proliferation and implies that the inactive state of PKM2 is associated with the proliferating cell population within tumors, whereas nonproliferating tumor cells require active pyruvate kinase. Consistent with these findings, variable PKM2 expression and heterozygous PKM2 mutations are found in human tumors. These data suggest that regulation of PKM2 activity supports the different metabolic requirements of proliferating and nonproliferating tumor cells.

Metformin decreases glucose oxidation and increases the dependency of prostate cancer cells on reductive glutamine metabolism

Metformin inhibits cancer cell proliferation, and epidemiology studies suggest an association with increased survival in patients with cancer taking metformin; however, the mechanism by which metformin improves cancer outcomes remains controversial. To explore how metformin might directly affect cancer cells, we analyzed how metformin altered the metabolism of prostate cancer cells and tumors. We found that metformin decreased glucose oxidation and increased dependency on reductive glutamine metabolism in both cancer cell lines and in a mouse model of prostate cancer. Inhibition of glutamine anaplerosis in the presence of metformin further attenuated proliferation, whereas increasing glutamine metabolism rescued the proliferative defect induced by metformin. These data suggest that interfering with glutamine may synergize with metformin to improve outcomes in patients with prostate cancer.

Abstract 4588: Identification of CDCP1 as a HIF-2α target gene involved in the regulation of cancer cell migration and metastasis

CUB domain-containing protein 1 (CDCP1) is a transmembrane protein that is highly expressed in stem cells and frequently overexpressed and tyrosine phosphorylated in cancer. CDCP1 promotes cancer cell metastasis. However, the mechanisms that regulate CDCP1 are not well defined. Studies from our laboratory revealed a biochemical pathway by which CDCP1 participates in the activation of Src-family kinase (SFK) members and the coupling of SFK-activation to the phosphorylation and regulation of protein kinase C-delta (PKC-δ). Here we show that hypoxia induces CDCP1 expression and tyrosine phosphorylation in a HIF-2α, but not HIF-1α, dependent fashion. shRNA knockdown of CDCP1 impairs cancer cell migration under hypoxic conditions, while overexpression of HIF-2α promotes the growth of tumor xenografts in association with enhanced CDCP1 expression and tyrosine phosphorylation, as well as, significantly promotes lung metastases in NOD/SCID mice. To investigate the relationship between HIF-2α and CDCP1 expression, we performed a correlation analysis in the largest up-to-date collection (Sanger Cell Line Project) of cancer cell line microarray data (n=732). We found a dramatic concordance in the expression of HIF-2α and CDCP1 (Pearson's correlation, P <1x10-20), indicating that cancers with high HIF-2α expression tend to have high levels of CDCP1 expression. We next asked whether other known HIF-2α target genes also correlate in this expression analysis. Remarkably, MET and EGFR, which are hypoxia regulated and known HIF-2α target genes, also displayed a strong correlation with HIF-2α and CDCP1 expression. Immunohistochemistry analysis of tissue microarray samples from tumors of patients with clear cell renal cell carcinoma (ccRCC) shows that increased CDCP1 expression correlates with decreased overall survival. Interestingly, high-grade ccRCCs (G3, G4) expressed significantly higher (P = 0.03, t-test) levels of CDCP1 protein compared to lower grade tumors (G1, G2), suggesting that CDCP1 expression increases progressively with higher ccRCC tumor grade. Furthermore, hypoxia activates Src signaling and the Src inhibitor (Dasatinib) prevents the hypoxia-induced phosphorylation of CDCP1. Thereby, reinforcing that CDCP1 is an SFK-associated receptor, which promotes migration and metastasis and suggests that hypoxia-induced CDCP1 signaling may further stimulate a more aggressive cancer phenotype. Together, these data support a critical role for CDCP1 as a unique HIF-2α target gene involved in the regulation of cancer metastasis, and suggest that therapeutic approaches targeting CDCP1, such as monoclonal antibodies, could be beneficial in the treatment of metastatic cancers.

Supported by NIH grant 5R01GM056203-15 to L.C.C and Dana Farber/Harvard Cancer Center Career Development Award to B.M.E.

Citation Format: Brooke M. Emerling, Cyril Benes, Eric Bell, George Poulogiannis, Kevin Courtney, Hui Lui, Rayman Choo-Wing, Gary Bellinger, Stephen Soltoff, Lewis Cantley. Identification of CDCP1 as a HIF-2α target gene involved in the regulation of cancer cell migration and metastasis. [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 4588. doi:10.1158/1538-7445.AM2013-4588

Abstract LB-365: Effective use of PI3K/MTOR and MEK inhibitors prior to hormone ablative therapy in PTEN-loss driven murine prostate cancer

The PTEN and p53 tumor suppressors are the most commonly altered genes in human cancer, including prostate cancer (PCa). Loss of PTEN is associated with increased Gleason score and clinical recurrence, and the majority of human metastatic PCas have PTEN loss via multiple mechanisms. Mice with prostate-specific homozygous deletion of PTEN develop invasive PCa albeit with prolonged latency of 6-8 months. Combined PTEN/p53 inactivation in mouse prostate elicits invasive cancer by 9 weeks of age and invariable lethality by 6 months of age. Since PTEN loss results in PI3K/mTOR pathway activation, we evaluated the impact of GSK458 (PI3K/mTOR inhibitor) and GSK418 (PI3K beta/delta isoform-specific inhibitor), singly and in combination with GSK212 (MEK inhibitor), in uncastrated, prostate-specific PTEN/p53 double knockout mice (4-6 months) and PTEN mice (11-14 months), respectively, harboring advanced PCa. The drugs were administered by daily oral gavage for 3 weeks with serial 18FDG-PET/MRI imaging at baseline, 2 days, 1 week, 2 weeks and 3 weeks post-treatment respectively. GSK458 treatment of PTEN/p53 and PTEN mice results in reduction in FDG-PET uptake as early as 24 h post-treatment, with 40% tumor shrinkage by 1 week post-treatment, but rapid regrowth of 18FDG-avid tumor by 2-3 weeks post-treatment. This acquired resistance was found to be mediated in part through upregulation of multiple receptor tyrosine kinases. In contrast, PTEN/p53 and PTEN mice did not respond to GSK418, by either FDG-PET or MRI analysis. We observed increased pERK/total ERK ratio by Western blot analysis and increased p-ERK staining by immunohistochemistry in GSK458 and GSK418-treated PTEN/53 mice, respectively. Treatment of PTEN/p53 and PTEN mice with GSK212 resulted in an approx. 40% reduction in tumor volume over 3 weeks. Treatment of PTEN/p53 mice with a combination of GSK458 plus GSK212 resulted in approx. 60% reduction of tumor volume at 3 week post-treatment. Strikingly, treatment of prostate-specific PTEN only mice with GSK458 plus GSK212 combination resulted in a >90% tumor regression at 3 weeks post-treatment. These results demonstrate the potential utlitity of PI3K/MEK-directed combination therapies in the neoadjuvant setting for locally advanced disease or hormone-sensitive phase in metastatic disease, thus delaying the need for hormone ablative therapy and its associated morbidity in advanced PCa. The data underscore the value of genetically engineered mouse models to co-clinically evaluate biomarkers of response and resistance to targeted therapies, and elucidate mechanisms of acquired resistance early in clinical development. The design of “personalized” combination therapies to overcome resistance to PI3K/MEK-directed therapies in the hormone-naive and castration-resistant contexts are currently underway in multiple GEMMs and Phase Ib co-clinical trials in advanced PCa.

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 LB-365. doi:1538-7445.AM2012-LB-365

Inhibition of pyruvate kinase M2 by reactive oxygen species contributes to cellular antioxidant responses

Control of intracellular reactive oxygen species (ROS) concentrations is critical for cancer cell survival. We show that, in human lung cancer cells, acute increases in intracellular concentrations of ROS caused inhibition of the glycolytic enzyme pyruvate kinase M2 (PKM2) through oxidation of Cys(358). This inhibition of PKM2 is required to divert glucose flux into the pentose phosphate pathway and thereby generate sufficient reducing potential for detoxification of ROS. Lung cancer cells in which endogenous PKM2 was replaced with the Cys(358) to Ser(358) oxidation-resistant mutant exhibited increased sensitivity to oxidative stress and impaired tumor formation in a xenograft model. Besides promoting metabolic changes required for proliferation, the regulatory properties of PKM2 may confer an additional advantage to cancer cells by allowing them to withstand oxidative stress.

Abstract LB-418: Targeting the PI3K/mTOR pathway in genetically engineered mouse models of prostate cancer

The PTEN and p53 tumor suppressors are among the most commonly inactivated or mutated genes in human cancer, including prostate cancer. Loss of PTEN is associated with increased pathologic Gleason score and risk of clinical recurrence, and 20-60% of human metastatic prostate cancers have loss of heterozygosity at the PTEN locus, resulting in hyperactivation of the PI3K/mTOR pathway. Mice with germline heterozygosity for PTEN have been shown to develop prostate intraepithelial neoplasia (PIN) at a high rate (>60%) and mice with prostate specific homozygous deletion of PTEN develop invasive prostate cancer, albeit with prolonged latency of approx. 6 months. Combined inactivation of PTEN and p53 in mouse prostate elicits invasive cancer by 9 weeks of age and invariable lethality by 7 months of age.

There are several PI3K pathway-directed therapies currently in Phase I clinical trials, but the underlying tumor genetic signature of patients most likely to respond to these therapies is largely unknown. To understand the significance of targeting the PI3K/mTOR pathway in advanced prostate cancer driven by PTEN +/− p53 loss, we evaluated the impact of GSK458 (a dual PI3K/mTOR inhibitor) in prostate-specific PTEN/p53 double knockout mice and prostate-specific PTEN-knockout mice. The mice were imaged by synchronized 18FDG-PET and T2-weighted MRI, respectively, for baseline tumor metabolic and volumetric assessment prior to drug administration. GSK458 was administered at 3 mg/kg by daily oral gavage for 3 weeks with serial 18FDG-PET and T2-weighted MRI imaging at 2 days, 1 week, 2 weeks and 3 weeks after initiation of treatment, followed by sacrifice, prostate harvest and standard hisopathologic and immunohistochemical staining.

GSK458 treatment of PTEN/p53-deficient and PTEN-deficient mice results in target inhibition, based on pharmacodynamic assessment by 18FDG-PET uptake. MRI and histopathologic analysis demonstrate that there is a significant reduction, but not complete regression of tumor burden in both intraepithelial and poorly differentiated atypical components within stroma and partial stromal collapse following 3 weeks of GSK458 treatment. These data highlight the feasibility of monitoring dual pharmacodynamics/antitumor effects of PI3K-directed therapies using 18FDG-PET/MRI imaging and underscore the utility of genetically engineered mouse models to predict response to targeted therapies in genetically stratified human clinical trials. The evaluation of PI3K-isoform specific inhibitors and the design of rational combinations to overcome de novo and acquired resistance mechanisms to PI3K-directed therapies are currently being explored in multiple genetically engineered mouse model systems.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-418. doi:10.1158/1538-7445.AM2011-LB-418

ErbB3 is required for ductal morphogenesis in the mouse mammary gland

Introduction

The receptor ErbB3/HER3 is often over-expressed in human breast cancers, frequently in conjunction with over-expression of the proto-oncogene ERBB2/HER2/NEU. Although the prognostic/predictive value of ErbB3 expression in breast cancer is unclear, ErbB3 is known to contribute to therapeutic resistance. Understanding ErbB3 functions in the normal mammary gland will help to explain its role in cancer etiology and as a modulator of signaling responses to the mammary oncogene ERBB2.

Methods

To investigate the roles of ErbB3 in mouse mammary gland development, we transplanted mammary buds from ErbB3^-/- embryos into the cleared mammary fat pads of wild-type immunocompromised mice. Effects on ductal outgrowth were analyzed at 4 weeks, 7 weeks and 20 weeks after transplantation for total ductal outgrowth, branch density, and number and area of terminal end buds. Sections of glands containing terminal end buds were analyzed for number and epithelial area of terminal end buds. Terminal end buds were also analyzed for presence of mitotic figures, apoptotic figures, BrdU incorporation, and expression of E-cadherin, P-cadherin, α-smooth muscle actin, and cleaved caspase-3.

Results

The mammary ductal trees developed from ErbB3^-/- buds only partly filled the mammary fat pad. In contrast to similar experiments with ErbB2^-/- mammary buds, this phenotype was maintained through adulthood, pregnancy, and parturition. In addition, and in contrast to similar work with ErbB4^-/- mammary buds, lobuloalveolar development of ErbB3^-/- transplanted glands was normal. The ErbB3^-/- mammary outgrowth defect was associated with a decrease in the size of the terminal end buds, and with increases in branch density, in the number of terminal end buds, and in the number of luminal spaces. Proliferation rates were not affected by the lack of ErbB3, but there was an increase in apoptosis in ErbB3^-/- terminal end buds.

Conclusions

Endogenous ErbB3 regulates morphogenesis of mammary epithelium.

Formation of Neu/ErbB2-induced mammary tumors is unaffected by loss of ErbB4

The four members of the ErbB family of receptor tyrosine kinases are involved in development and tumorigenesis of the mammary gland. Whereas the epidermal growth factor receptor, ErbB2 and ErbB3 are positively associated with various cancers, clinical studies of ErbB4 in breast cancer are contradictory. Results from tissue culture analyses and some clinical studies suggested that ErbB4 is either a tumor suppressor or is a negative regulator of ErbB2-driven tumors. Neu-Cre-ErbB4(flox/null) mice in which ErbB4 was inactivated by Cre-lox-mediated recombination in the mammary gland developed MMTV-Neu-driven mammary tumors with a similar latency period to mice with one or two wild-type ErbB4 alleles. Moreover, there was no difference in the histologies of tumors that developed, nor in the propensity to form lung metastases. Taken together these results suggest that ErbB4 is not a potent, highly penetrant tumor suppressor, nor is it a factor in Neu-mediated tumorigenesis in this model.

ErbB2 is required for ductal morphogenesis of the mammary gland

The ERBB2/HER2/NEU receptor tyrosine kinase gene is amplified in up to 30% of human breast cancers. The frequent and specific selection of this receptor kinase gene for amplification in breast cancer implies that it has important normal functions in the mammary gland. To investigate the functions of ErbB2 during normal mouse mammary gland development, we transplanted mammary buds from genetically rescued ErbB2(-/-) embryos that express ErbB2 in the cardiac muscle. ErbB2(-/-) mammary buds transplanted to a wild-type mammary fat pad support outgrowth of an epithelial tree that advances only slowly through the mammary fat pad at puberty. This penetration defect is associated with structural defects in terminal end buds, characterized by a decrease in body cell number, an increased presence of cap-like cells in the prelumenal compartment, and the presence of large luminal spaces. Lobuloalveolar development was not affected in glands that developed from ErbB2(-/-) transplanted tissue. The results may have implications for the aggressive phenotypes associated with ERBB2-overexpressing mammary carcinomas.