Fernández-Zapico, Martín E.

Abstract We have demonstrated that crosstalk between the Hedgehog-GLI-GLI and EGFR signaling pathway exists and contribute to pancreatic tumorigenesis. This interaction can be abrogated by targeting both pathways simultaneously and results in a synergistic antitumor effect in vitro and in vivo in pancreatic tumor models. Based on these results we have undertaken a phase I trial of GDC-0449 (an orally administered Hedgehog pathway inhibitor) and erlotinib (EGFR tyrosine kinase inhibitor to: 1) determine the maximally tolerated dose (MTD) of GDC-0449 combined with erlotinib in unresectable solid tumors; 2) describe the adverse events associated with this treatment combination; 3) describe the responses of this treatment combination; and 4) to assess the effect of the erlotinib and GDC-0449 combination on selected biomarkers in circulating tumor cells (CTCs), tumor biopsies, and FDG-PET in a cohort of patients with metastatic pancreatic cancer patients treated at the MTD. During the dose escalation portion of the trial, eligible patients receive GDC-0449 150 mg p.o. daily and erlotinib 50, 75, 100, or 150 mg daily p.o. at dose levels 1, 2, 3, and 4 respectively. Eligibility criteria include: histologic proof of solid tumors that are unresectable, not amenable to any other standard therapies, or patient refused standard therapy,; ANC ≥> 1500/μL; PLT ≥> 100,000/ μL; Total bilirubin ≤< upper limit of normal (ULN); AST ≤< 3 x ULN; Creatinine ≤< 1.5 x ULN; Hemoglobin ≥> 9.0 g/dL; INR within normal limits (Cohort II [MTD Cohort] only); ECOG performance status (PS) 0, 1 or ≤ 2. For the MTD cohort, only patients with metastatic adenocarcinoma of the pancreas without prior systemic therapy for metastatic disease and tumor amenable to biopsies are eligible. Toxicity assessment is performed at each 28-day treatment cycles and response assessment every second treatment 28 day cycle. 12 patients have been entered-pancreas (3), colorectal (3), neuroendocrine (2), scc anus (2), gallbladder (1), thymoma (1). No dose-limiting toxicity (DLT) was reported at dose level 4. At the MTD, up to 20 patients with previously untreated metastatic pancreatic cancer will be entered to assess the biologic effect of GDC-0449+erlotinib. Pre- and post- treatment biopsies of metastases and FDG-PET will be performed. Weekly collection of CTCs will be undertaken and immunofluorescence microscopy of total & phosphoMAPK, EGFR, AKT, PATCHED1, GLI1, BCL-2, and quantitative PCR (Q-PCR) of PATCHED1, GLI1, and its target genes (BCL-2, BFL-1/A1, 4-1BB) will be performed. In addtion, total & phosphoMAPK, EGFR, and AKT, as well as PATCHED1, GLI1, BCL-2 by immunohistochemistry and Q-PCR of PATCHED1, GLI1, BCL-2, BFL-1/A1, 4-1BB will be analyzed in tumor biopsies. Supported by CA69912, CA136526 and CA102701. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 1807.

Abstract Crosstalk between signaling pathways is crucial to the initiation, progression and maintenance of the transformed phenotype. Therefore, characterization of these signaling interactions is fundamental for the understanding of the complex and varied network of events that leads to the development and spread of tumors. The Hedgehog (HH)-GLI pathway, an important carcinogenic cascade, is required for the growth and survival of tumors of diverse origin. Recent reports, mainly from animal models, suggest that key signaling interactions are required by HH-GLI signaling to modulate cancer-associated cellular functions. However, the molecular mechanisms underlying this phenomenon in cancer and non-cancer cells remain elusive. Our preliminary data show a crosstalk between the HH-GLI axis and TGF-beta pathway, a well-characterized tumor suppressor/oncogenic signaling pathway. Luciferase reporter and expression assays in combination with genetic and pharmacological manipulations of the TGFbeta pathway show that this cascade is able to activate GLI transcriptional activity, even in the absence of an active HH signaling. The TGFbeta pathway is required to maintain active GLI transcriptional complexes at GLI target genes. Further analysis of this molecular interaction suggests that TGFbeta pathway-mediated activation of GLI transcription factors requires an intact SMAD4, thus suggesting a potential mechanism mediating this functional interaction. The knowledge derived from this study provides both mechanistic insight into the contribution of this HH-GLI/TGF-beta pathway interaction to carcinogenesis and could serve as a foundation for development of new therapeutic approaches for tumors with active HH-GLI and TGF cascades. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3917.

SP/KLF (Specificity protein/Krüppel-like factor) transcription factors comprise an emerging group of proteins that may behave as tumour suppressors. Incidentally, many cancers that display alterations in certain KLF proteins are also associated with a high incidence of KRAS (V-Ki-ras2 Kirsten rat sarcoma viral oncogene homologue) mutations. Therefore in the present paper we investigate whether SP/KLF proteins suppress KRAS-mediated cell growth, and more importantly, the potential mechanisms underlying these effects. Using a comprehensive family-wide screening of the 24 SP/KLF members, we discovered that SP5, SP8, KLF2, KLF3, KLF4, KLF11, KLF13, KLF14, KLF15 and KLF16 inhibit cellular growth and suppress transformation mediated by oncogenic KRAS. Each protein in this subset of SP/KLF members individually inhibits BrdU (5-bromo-2-deoxyuridine) incorporation in KRAS oncogenic-mutant cancer cells. SP5, KLF3, KLF11, KLF13, KLF14 and KLF16 also increase apoptosis in these cells. Using KLF11 as a representative model for mechanistic studies, we demonstrate that this protein inhibits the ability of cancer cells to form both colonies in soft agar and tumour growth in vivo. Molecular studies demonstrate that these effects of KLF11 are mediated, at least in part, through silencing cyclin A via binding to its promoter and leading to cell-cycle arrest in S-phase. Interestingly, similar to KLF11, KLF14 and KLF16 mechanistically share the ability to modulate the expression of cyclin A. Collectively, the present study stringently defines a distinct subset of SP/KLF proteins that impairs KRAS-mediated cell growth, and that mechanistically some members of this subset accomplish this, at least in part, through regulation of the cyclin A promoter.

Abstract Reflux-induced injury promotes esophageal adenocarcinoma, one of the most rapidly increasing, highly lethal cancers in Western countries. Here, we investigate the efficacy of a combinatorial chemoprevention strategy for esophageal adenocarcinoma and characterize the underlying molecular mechanisms. Specifically, our approach involves the use of ursodeoxycholic acid (Urso) due to its ability to decrease injury-inducing bile salts in combination with Aspirin to mitigate the consequences of injury. We find that Urso-Aspirin combination reduces the risk of adenocarcinoma in vivo in animals with reflux, decreases the proliferation of esophageal adenocarcinoma cells, and downregulates a key cell cycle regulator, CDK2. Mechanistically, using cell growth, luciferase reporter, expression, and chromatin immunoprecipitation assays, we identify GLI1, a Hedgehog-regulated transcription factor, as a novel target of Urso-Aspirin combination. We show that GLI1 is upregulated during esophageal carcinogenesis, and GLI1 can bind to the CDK2 promoter and activate its expression. Although the Urso-Aspirin combination downregulates GLI1, the GLI1 overexpression not only abrogates the effect of this combination on proliferation but it also restores CDK-2 expression. These findings support that the chemopreventive effect of the Urso-Aspirin combination occurs, at least in part, through a novel GLI1-CDK2–dependent mechanism. To further understand the regulation of CDK2 by GLI1, both pharmacologic and RNAi-mediated approaches show that GLI1 is a transcriptional activator of CDK2, and this regulation occurs independent of Smoothened, the central transducer of the Hedgehog canonical pathway. Collectively, these results identify a novel GLI1-to-CDK2 pathway in esophageal carcinogenesis, which is a bona fide target for effective combinatorial chemoprevention with Urso and Aspirin. Cancer Res; 70(17); 6787–96. ©2010 AACR.

Abstract Chronic lymphocytic leukemia (CLL) is commonly defined as a disease of failed apoptosis of B cells and remains an incurable disease. The mechanism of resistance to apoptosis in CLL is complex and influenced by numerous factors, including nuclear factor κB (NFκB)-mediated expression of antiapoptotic molecules. Recent evidence indicates that glycogen synthase kinase-3β (GSK-3β) positively regulates NFκB-mediated gene transcription and cell survival. Using malignant B cells collected from patients with CLL, we find that both GSK-3β and NFκB accumulate in the nucleus of CLL B cells, and pharmacologic inhibition of GSK-3 results in decreased expression of two NFκB target genes Bcl-2 and XIAP and a subsequent increase in CLL B-cell apoptosis ex vivo. Furthermore, we observed that inhibition of GSK-3 leads to a decrease in NFκB-mediated gene transcription but does not affect the nuclear accumulation of NFκB in CLL B cells. Last, using chromatin immunoprecipitation, we show that GSK-3 inhibition abrogates NFκB binding to its target gene promoters (XIAP, Bcl-2), in part through epigenetic modification of histones. Our results establish that inhibition of GSK-3 abrogates NFκB binding to its target gene promoters through an epigenetic mechanism, enhances apoptosis in CLL B cells ex vivo and identifies GSK-3 as a potential therapeutic target in the treatment of CLL.

Abstract Purpose: We have shown recently that glycogen synthase kinase-3 (GSK-3) β regulates nuclear factor-κB (NF-κB)–mediated pancreatic cancer cell survival and proliferation in vitro. Our objective was to determine the localization of GSK-3β in pancreatic cancer cells and assess the antitumor effect of GSK-3 inhibition in vivo to improve our understanding of the mechanism by which GSK-3β affects NF-κB activity in pancreatic cancer. Experimental Design: Immunohistochemistry and cytosolic/nuclear fractionation were done to determine the localization of GSK-3β in human pancreatic tumors. We studied the effect of GSK-3 inhibition on tumor growth, cancer cell proliferation, and survival in established CAPAN2 tumor xenografts using a tumor regrowth delay assay, Western blotting, bromodeoxyuridine incorporation, and terminal deoxynucleotidyl transferase–mediated dUTP nick end labeling. Results: We found nuclear accumulation of GSK-3β in pancreatic cancer cell lines and in 62 of 122 (51%) human pancreatic adenocarcinomas. GSK-3β nuclear accumulation is significantly correlated with human pancreatic cancer dedifferentiation. We have found that active GSK-3β can accumulate in the nucleus of pancreatic cancer cells and that inhibition of GSK-3 kinase activity represses its nuclear accumulation via proteasomal degradation within the nucleus. Lastly, we have found that inhibition of GSK-3 arrests pancreatic tumor growth in vivo and decreases NF-κB-mediated pancreatic cancer cell survival and proliferation in established tumor xenografts. Conclusions: Our results show the antitumor effect of GSK-3 inhibition in vivo, identify GSK-3β nuclear accumulation as a hallmark of poorly differentiated pancreatic adenocarcinoma, and provide new insight into the mechanism by which GSK-3β regulates NF-κB activity in pancreatic cancer.

Gentamicin is a widely used ototoxic agent. In this study, we shed light on the mechanisms underlying gentamicin-induced hearing loss. More importantly, we demonstrate in vivo and in vitro the effectiveness of a strategy for preventing drug-induced hearing loss using l -carnitine (LCAR), a safe micronutrient that plays a key role in energy metabolism and detoxification [Rebouche, C. J. & Seim, H. (1998) Annu. Rev. Nutr. 18, 39-61]. We show that LCAR prevents changes in hearing threshold and cochlear damage in newborn guinea pigs exposed to gentamicin in utero . Mechanistically, gentamicin-induced apoptosis of auditory cells is mediated by the extracellular signal-regulated kinase (ERK) 1/2 mitogen-activated protein kinase (MAPK) pathway through up-regulation of the proapoptotic factor Harakiri ( Hrk ). Most important, small interfering RNA (siRNA) experiments demonstrate that Hrk up-regulation is crucial for gentamicin-induced apoptosis. LCAR, in contrast, prevents both gentamicin-induced Hrk up-regulation and apoptosis acting by means of c-Jun N-terminal kinase (JNK). Together, these results outline pathways for gentamicin-induced hearing loss and its prevention and assign a key role to Hrk in these processes. Thus, our data offer a conceptual framework for designing clinical trials using a safe micronutrient, LCAR, as a simple preventive strategy for iatrogenically induced ototoxicity.

Abstract Recent studies using glycogen synthase kinase-3β (GSK-3β)–deficient mouse embryonic fibroblasts suggest that GSK-3β positively regulates nuclear factor κB (NFκB)–mediated gene transcription. Because NFκB is suggested to participate in cell proliferation and survival pathways in pancreatic cancer, we investigated the role of GSK-3β in regulating these cellular processes. Herein, we show that pancreatic cancer cells contain a pool of active GSK-3β and that pharmacologic inhibition of GSK-3 kinase activity using small molecule inhibitors or genetic depletion of GSK-3β by RNA interference leads to decreased cancer cell proliferation and survival. Mechanistically, we show that GSK-3β influences NFκB-mediated gene transcription at a point distal to the Iκ kinase complex, as only ectopic expression of the NFκB subunits p65/p50, but not an Iκ kinase β constitutively active mutant, could rescue the decreased cellular proliferation and survival associated with GSK-3β inhibition. Taken together, our results simultaneously identify a previously unrecognized role for GSK-3β in cancer cell survival and proliferation and suggest GSK-3β as a potential therapeutic target in the treatment of pancreatic cancer.

KLF11 (TIEG2) is a pancreas-enriched transcription factor that has elicited significant attention because of its role as negative regulator of exocrine cell growth in vitro and in vivo . However, its functional role in the endocrine pancreas remains to be established. Here, we report, for the first time, to our knowledge, the characterization of KLF11 as a glucose-inducible regulator of the insulin gene. A combination of random oligonucleotide binding, EMSA, luciferase reporter, and chromatin immunoprecipitation assays shows that KLF11 binds to the insulin promoter and regulates its activity in beta cells. Genetic analysis of the KLF11 gene revealed two rare variants (Ala347Ser and Thr220Met) that segregate with diabetes in families with early-onset type 2 diabetes, and significantly impair its transcriptional activity. In addition, analysis of 1,696 type 2 diabetes mellitus and 1,776 normoglycemic subjects show a frequent polymorphic Gln62Arg variant that significantly associates with type 2 diabetes mellitus in North European populations (OR = 1.29, P = 0.00033). Moreover, this variant alters the corepressor mSin3A-binding activity of KLF11, impairs the activation of the insulin promoter and shows lower levels of insulin expression in pancreatic beta cells. In addition, subjects carrying the Gln62Arg allele show decreased plasma insulin after an oral glucose challenge. Interestingly, all three nonsynonymous KLF11 variants show increased repression of the catalase 1 promoter, suggesting a role in free radical clearance that may render beta cells more sensitive to oxidative stress. Thus, both functional and genetic analyses reveal that KLF11 plays a role in the regulation of pancreatic beta cell physiology, and its variants may contribute to the development of diabetes.