Kyle McElyea

Applying Small Molecule Signal Transducer and Activator of Transcription-3 (STAT3) Protein Inhibitors as Pancreatic Cancer Therapeutics

Constitutively activated STAT3 protein has been found to be a key regulator of pancreatic cancer and a target for molecular therapeutic intervention. In this study, PG-S3-001, a small molecule derived from the SH-4-54 class of STAT3 inhibitors, was found to inhibit patient-derived pancreatic cancer cell proliferation in vitro and in vivo in the low micromolar range. PG-S3-001 binds the STAT3 protein potently, Kd = 324 nmol/L by surface plasmon resonance, and showed no effect in a kinome screen (>100 cancer-relevant kinases). In vitro studies demonstrated potent cell killing as well as inhibition of STAT3 activation in pancreatic cancer cells. To better model the tumor and its microenvironment, we utilized three-dimensional (3D) cultures of patient-derived pancreatic cancer cells in the absence and presence of cancer-associated fibroblasts (CAF). In this coculture model, inhibition of tumor growth is maintained following STAT3 inhibition in the presence of CAFs. Confocal microscopy was used to verify tumor cell death following treatment of 3D cocultures with PG-S3-001. The 3D model was predictive of in vivo efficacy as significant tumor growth inhibition was observed upon administration of PG-S3-001. These studies showed that the inhibition of STAT3 was able to impact the survival of tumor cells in a relevant 3D model, as well as in a xenograft model using patient-derived cells. Mol Cancer Ther; 15(5); 794–805. ©2016 AACR.

A phase II trial of dovitinib in BCG-unresponsive urothelial carcinoma with FGFR3 mutations or overexpression: Hoosier Cancer Research Network trial HCRN 12-157

Purpose: To assess the clinical and pharmacodynamic activity of dovitinib in a treatment-resistant, molecularly enriched non–muscle-invasive urothelial carcinoma of the bladder (NMIUC) population. Experimental Design: A multi-site pilot phase II trial was conducted. Key eligibility criteria included the following: Bacillus Calmette-Guerin (BCG)-unresponsive NMIUC (>2 prior intravesical regimens) with increased phosphorylated FGFR3 (pFGFR3) expression by centrally analyzed immunohistochemistry (IHC+) or FGFR3 mutations (Mut+) assessed in a CLIA-licensed laboratory. Patients received oral dovitinib 500 mg daily (5 days on/2 days off). The primary endpoint was 6-month TURBT-confirmed complete response (CR) rate. Results: Between 11/2013 and 10/2014, 13 patients enrolled (10 IHC+ Mut−, 3 IHC+ Mut+). Accrual ended prematurely due to cessation of dovitinib clinical development. Demographics included the following: median age 70 years; 85% male; carcinoma in situ (CIS; 3 patients), Ta/T1 (8 patients), and Ta/T1 + CIS (2 patients); median prior regimens 3. Toxicity was frequent with all patients experiencing at least one grade 3–4 event. Six-month CR rate was 8% (0% in IHC+ Mut−; 33% in IHC+ Mut+). The primary endpoint was not met. Pharmacodynamically active (94–5,812 nmol/L) dovitinib concentrations in urothelial tissue were observed in all evaluable patients. Reductions in pFGFR3 IHC staining were observed post-dovitinib treatment. Conclusions: Dovitinib consistently achieved biologically active concentrations within the urothelium and demonstrated pharmacodynamic pFGFR3 inhibition. These results support systemic administration as a viable approach to clinical trials in patients with NMIUC. Long-term dovitinib administration was not feasible due to frequent toxicity. Absent clinical activity suggests that patient selection by pFGFR3 IHC alone does not enrich for response to FGFR3 kinase inhibitors in urothelial carcinoma. Clin Cancer Res; 23(12); 3003–11. ©2016 AACR.

Critical role of phosphorylation of serine 165 of YBX1 on the activation of NF-κB in colon cancer

Y-box binding protein 1 [YBX1] is a multifunctional protein known to facilitate many of the hallmarks of cancer. Elevated levels of YBX1 protein are highly correlated with cancer progression, making it an excellent marker in cancer. The connection between YBX1 and the important nuclear factor κB [NF-κB] has never been reported. Here, we show that overexpression of wild type YBX1 [WT-YBX1] activates NF-κB, suggesting that YBX1 is a potential NF-κB activator. Furthermore, using mass spectrometry analysis we identified novel phosphorylation of serine 165 [S165] on YBX1. Overexpression of the S165A-YBX1 mutant in either HEK293 cells or colon cancer HT29 cells showed dramatically reduced NF-κB activating ability as compared with that of WT-YBX1, confirming that S165 phosphorylation is critical for the activation of NF-κB by YBX1. We also show that expression of the S165A-YBX1 mutant dramatically decreased the expression of NF-κB-inducible genes, reduced cell growth, and compromised tumorigenic ability as compared with WT-YBX1. Taken together, we provide the first evidence that YBX1 functions as a tumor promoter via NF-κB activation, and phosphorylation of S165 of YBX1 is critical for this function. Therefore, our important discovery may lead to blocking S165 phosphorylation as a potential therapeutic strategy to treat colon cancer.

Early-Stage Metastasis Requires Mdm2 and Not p53 Gain of Function

Metastasis of cancer cells to distant organ systems is a complex process that is initiated with the programming of cells in the primary tumor. The formation of distant metastatic foci is correlated with poor prognosis and limited effective treatment options. We and others have correlated Mouse double minute 2 (Mdm2) with metastasis; however, the mechanisms involved have not been elucidated. Here, it is reported that shRNA-mediated silencing of Mdm2 inhibits epithelial–mesenchymal transition (EMT) and cell migration. In vivo analysis demonstrates that silencing Mdm2 in both post-EMT and basal/triple-negative breast cancers resulted in decreased primary tumor vasculature, circulating tumor cells, and metastatic lung foci. Combined, these results demonstrate the importance of Mdm2 in orchestrating the initial stages of migration and metastasis. Implication: Mdm2 is the major factor in the initiation of metastasis. Mol Cancer Res; 15(11); 1598–607. ©2017 AACR.

Dependence receptor UNC5A restricts luminal to basal breast cancer plasticity and metastasis

BackgroundThe majority of estrogen receptor-positive (ERα+) breast cancers respond to endocrine therapies. However, resistance to endocrine therapies is common in 30% of cases, which may be due to altered ERα signaling and/or enhanced plasticity of cancer cells leading to breast cancer subtype conversion. The mechanisms leading to enhanced plasticity of ERα-positive cancer cells are unknown.MethodsWe used short hairpin (sh)RNA and/or the CRISPR/Cas9 system to knockdown the expression of the dependence receptor UNC5A in ERα+ MCF7 and T-47D cell lines. RNA-seq, quantitative reverse transcription polymerase chain reaction, chromatin immunoprecipitation, and Western blotting were used to measure the effect of UNC5A knockdown on basal and estradiol (E2)-regulated gene expression. Mammosphere assay, flow cytometry, and immunofluorescence were used to determine the role of UNC5A in restricting plasticity. Xenograft models were used to measure the effect of UNC5A knockdown on tumor growth and metastasis. Tissue microarray and immunohistochemistry were utilized to determine the prognostic value of UNC5A in breast cancer. Log-rank test, one-way, and two-way analysis of variance (ANOVA) were used for statistical analyses.ResultsKnockdown of the E2-inducible UNC5A resulted in altered basal gene expression affecting plasma membrane integrity and ERα signaling, as evident from ligand-independent activity of ERα, altered turnover of phosphorylated ERα, unique E2-dependent expression of genes effecting histone demethylase activity, enhanced upregulation of E2-inducible genes such as BCL2, and E2-independent tumorigenesis accompanied by multiorgan metastases. UNC5A depletion led to the appearance of a luminal/basal hybrid phenotype supported by elevated expression of basal/stem cell-enriched ∆Np63, CD44, CD49f, epidermal growth factor receptor (EGFR), and the lymphatic vessel permeability factor NTN4, but lower expression of luminal/alveolar differentiation-associated ELF5 while maintaining functional ERα. In addition, UNC5A-depleted cells acquired bipotent luminal progenitor characteristics based on KRT14+/KRT19+ and CD49f+/EpCAM+ phenotype. Consistent with in vitro results, UNC5A expression negatively correlated with EGFR expression in breast tumors, and lower expression of UNC5A, particularly in ERα+/PR+/HER2− tumors, was associated with poor outcome.ConclusionThese studies reveal an unexpected role of the axon guidance receptor UNC5A in fine-tuning ERα and EGFR signaling and the luminal progenitor status of hormone-sensitive breast cancers. Furthermore, UNC5A knockdown cells provide an ideal model system to investigate metastasis of ERα+ breast cancers.

Pharmacological Dual Inhibition of Tumor and Tumor-Induced Functional Limitations in a Transgenic Model of Breast Cancer

Breast cancer progression is associated with systemic effects, including functional limitations and sarcopenia without the appearance of overt cachexia. Autocrine/paracrine actions of cytokines/chemokines produced by cancer cells mediate cancer progression and functional limitations. The cytokine-inducible transcription factor NF-κB could be central to this process, as it displays oncogenic functions and is integral to the Pax7:MyoD:Pgc-1β:miR-486 myogenesis axis. We tested this possibility using the MMTV-PyMT transgenic mammary tumor model and the NF-κB inhibitor dimethylaminoparthenolide (DMAPT). We observed deteriorating physical and functional conditions in PyMT+ mice with disease progression. Compared with wild-type mice, tumor-bearing PyMT+ mice showed decreased fat mass, impaired rotarod performance, and reduced grip strength as well as increased extracellular matrix (ECM) deposition in muscle. Contrary to acute cachexia models described in the literature, mammary tumor progression was associated with reduction in skeletal muscle stem/satellite-specific transcription factor Pax7. Additionally, we observed tumor-induced reduction in Pgc-1β in muscle, which controls mitochondrial biogenesis. DMAPT treatment starting at 6 to 8 weeks age prior to mammary tumor occurrence delayed mammary tumor onset and tumor growth rates without affecting metastasis. DMAPT overcame cancer-induced functional limitations and improved survival, which was accompanied with restoration of Pax7, Pgc-1β, and mitochondria levels and reduced ECM levels in skeletal muscles. In addition, DMAPT restored circulating levels of 6 out of 13 cancer-associated cytokines/chemokines changes to levels seen in healthy animals. These results reveal a pharmacological approach for overcoming cancer-induced functional limitations, and the above-noted cancer/drug-induced changes in muscle gene expression could be utilized as biomarkers of functional limitations. Mol Cancer Ther; 16(12); 2747–58. ©2017 AACR.

Abstract 5183: Efficacy study of APX3330, a Ref-1 redox inhibitor, and Gemcitabine in a mouse pancreatic ductal adenocarcinoma model

High levels of apurinic/apyrimidinic endonuclease/redox factor 1 (APE1/Ref-1 or Ref-1) expression have been reported in numerous cancers such that Ref-1 is an emerging target in a variety of cancer types. Ref-1 is a dual function protein with both DNA repair activity as well as redox activity. Ref-1 is responsible for the repair of baseless sites in DNA caused by alkylation and oxidative DNA damage as well as regulating several transcription factors including HIF-1a, NFkB, AP-1, and STAT3. Using siRNA to knockdown Ref-1 in pancreatic ductal adenocarcinoma (PDAC) cells (MIA-PaCa-2), we quantitated Ref-1 expression following transfection with scrambled control and Ref-1 siRNA using Indica Lab9s HALO CytoNuclear software. Knockdown of greater than 85% greatly decreases the proliferation of PDAC cells, and supports Ref-1 as a target in pancreatic cancer. To assess the efficacy of targeting Ref-1 in vivo, a small molecule Ref-1 redox inhibitor, APX3330, was used in combination therapy with a PDAC standard of care agent, Gemcitabine, in a PDAC xenograft mouse model. In this study, NSG mice were treated with: Gemcitabine (35mg/kg), APX3330 (12.5, 25, and 50mg/kg), and combinations of APX3330 and Gemcitabine (12.5, 25, and 50mg/kg), as well as a vehicle control group. At termination of the study, tumors were harvested, tissue sections prepared, stained for HE 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5183.