Citations

Objectives Two independently developed Ptf1a-Cre mouse lines, Ptf1atm1(cre)Hnak and Ptf1atm1(Cre)Cvw, are widely used in pancreatic research. Recently, Ptf1atm1(cre)Hnak line was reported to transmit unwanted paternal recombination. We aimed to investigate whether this exists in the Ptf1atm1(Cre)Cvw line. Methods Ptf1atm1(Cre)Cvw mice were crossed with R26-LSL-LacZ reporter mice. DNA recombination and gene expression were examined by recombination-specific polymerase chain reaction, reverse transcription–polymerase chain reaction, and X-Gal staining. Results R26 locus recombination was detected in the pancreas as well as the testes and sperm of the double transgenic mice. Positive ptf1a mRNA expression from testes revealed that there was endogenous Ptf1a promoter activity in this extrapancreatic tissue. Of the 15 progenies that inherited LacZ from the male double transgenic mice, 4 (26.7%) were positive for complete whole-body recombination. The presence of recombination in R26 only mice suggested that the recombination occurred before meiosis. Conclusions Paternal germline recombination exists in the Ptf1atm1(Cre)Cvw mouse line. Ptf1a promoter-driven Cre expression during spermatogenesis before meiosis is the cause of germline recombination. Therefore, when male Ptf1a-Cre mice are used in compound mice breeding, it is necessary to genotype not only floxed alleles but also recombined alleles to examine unwanted recombinations.

Protein kinase C iota (PKCι) functions as a bonafide human oncogene in lung and ovarian cancer and is required for KrasG12D-mediated lung cancer initiation and progression. PKCι expression is required for pancreatic cancer cell growth and maintenance of the transformed phenotype; however, nothing is known about the role of PKCι in pancreas development or pancreatic tumorigenesis. In this study, we investigated the effect of pancreas-specific ablation of PKCι expression on pancreatic cellular homeostasis, susceptibility to pancreatitis, and KrasG12D-mediated pancreatic cancer development. Knockout of pancreatic Prkci significantly increased pancreatic immune cell infiltration, acinar cell DNA damage, and apoptosis, but reduced sensitivity to caerulein-induced pancreatitis. Prkci-ablated pancreatic acinar cells exhibited P62 aggregation and a loss of autophagic vesicles. Loss of pancreatic Prkci promoted KrasG12D-mediated pancreatic intraepithelial neoplasia formation but blocked progression to adenocarcinoma, consistent with disruption of autophagy. Our results reveal a novel promotive role for PKCι in pancreatic epithelial cell autophagy and pancreatic cancer progression.

Abstract The development of pancreatic cancer requires both obtain of oncogenic Kras mutations and up-regulation of growth factor signaling. However, how oncogenic Kras regulates growth factor signaling in pancreatic cancer development is still unclear. Using a transgenic mouse model harboring an oncogenic Kras mutation and a 3D organoid explant culture of primary pancreatic acini, we here show that expression of mutant Kras in pancreatic acinar cells alters their mitochondrial metabolism, resulting in increased generation of mitochondrial reactive oxygen species (mROS). We further demonstrate that mROS induced by oncogenic Kras is required for transdifferentiating acinar cells to a duct-like phenotype and eventually progression to pancreatic intraepithelial neoplasia (PanIN), the most common precursor lesions of pancreatic ductal adenocarcinoma (PDAC). This transdiffentiation process is mediated by increased levels of epidermal growth factor receptor (EGFR) as well as its ligands, EGF and TGFα, through activation of the ROS-receptive transcription factors, NF-κB1 and NF-κB2. In Kas transgenic mice, the interception of KrasG12D-mediated generation of mROS significantly reduced the formation of pre-neoplastic lesions. Hence, our data provide mechanistic insight of how oncogenic Kras mutant crosstalks with growth factor signaling to cause the formation of pancreatic cancer. Citation Format: Geou-Yarh Liou, Heike Doeppler, Kathleen E. DelGirono, Howard C. Crawford, Michael P. Murphy, Peter Storz. Oncogenic Kras-induced mitochondrial oxidative stress in pancreatic acini modulates the formation of precancerous lesions through autocrine EGFR signaling. [abstract]. In: Proceedings of the Fourth AACR International Conference on Frontiers in Basic Cancer Research; 2015 Oct 23-26; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2016;76(3 Suppl):Abstract nr PR01.

Abstract Prior to PanIN formation, acinar cells harboring oncogenic Kras gradually lose their acinar character and take on a ductal phenotype in a process known as acinar-to-ductal metaplasia. Rather than mimicking a normal pancreatic duct, metaplastic ducts take on a proliferative biliary progenitor phenotype, marked by the expression of SOX17 and PDX1 and the presence of numerous tuft cells, recently identified as a PanIN initiating cells. Manipulation of SOX17 and PDX1 in vivo reveal them to be a transdifferentiation promoter and suppressor, respectively, both greatly affecting tuft cell genesis and tumor formation. These opposing roles of developmental transcription factors during tumorigenesis implicate the usurpation of a differentiation program that significantly contributes to cellular heterogeneity within early pre-cancerous lesions of the pancreas. Citation Format: Kenneth K. Takeuchi, Kathleen E. Delgiorno, Christopher J. Halbrook, Howard C. Crawford. Acinar cell transdifferentiation sets the stage for early tumor heterogeneity. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr IA13.

Abstract Pancreatic adenocarcinoma (PDAC) is the 4th most common cause of cancer related deaths in the United States and has a dismal 5-year survival rate of 6%. This prognosis is attributed the disease’s fast and asymptomatic progression to metastasis, leading to late diagnosis upon which time there are few treatment options available. The A Disintegrin and Metalloproteinase (ADAM) family are sheddase proteins known to regulate cell adhesion and function. This regulation can allow ADAMs to influence the ability of tumor cells to disseminate from the primary tumor and metastasize to distant organs. ADAM10, which is seen to be up-regulated in both chronic pancreatitis and PDAC, cleaves a variety of substrates including several cell adhesion molecules such as L1-CAM, N-Cadherin, and E-Cadherin. Using a conditional knockout for ADAM10 in the Kras+/G12D;Ptf1a+/Cre (KC) mouse model of pancreatic cancer, we have observed an absence of metastasis when ADAM10 is genetically ablated. To investigate the potential role that ADAM10 plays in this, we used a shRNA approach to knock-down ADAM10 expression in various human pancreatic cancer cells lines. Analysis of these cell lines suggests a partial restoration of a less aggressive, differentiated phenotype, consistent with the increased longevity of the ADAM10 knockout KC mice. Citation Format: Louise V. Peverley, Christopher J. Halbrook, Jason C. Hall, Christine M. Ardito, Howard C. Crawford. Investigating the role of ADAM10 in pancreatic tumor differentiation. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A77.

Abstract The EGFR and Notch signaling pathways have been widely implicated in relation to both chronic pancreatitis and pancreatic ductal adenocarcinoma in humans, however the link between the two pathways has remained obscure. Acinar to ductal metaplasia (ADM,) a phenomenon where acinar cells undergo a morphological change and begin expressing markers normally found only in ductal cells while losing markers typical of acinar cells, has been linked to both the Notch and EGFR signaling pathways. ADM is highly proliferative with the potential to develop into pancreatic intraepithelial neoplasia, a precursor lesion to pancreatic cancer. Recently we and others have shown that genetic ablation of EGFR in the pancreas effectively prevents acinar to ductal metaplasia in cerulein model of pancreatitis in mice, and prevents tumorigenesis driven by oncogenic Kras. Additionally, we have found that acinar cells harvested from EGFRf/f;Ptf1aCre/+ mice (EKO) mice are resistant to ADM in vitro upon cerulein treatment, or by the expression of oncogenic Kras. Activation of EGFR by treatment of WT collagen embedded acinar cell explants with the EGFR ligand TGF-α has previously been shown to induce ADM in a manner requiring Notch pathway activation. Furthermore, it has also been demonstrated that expression of Notch2 intracellular domain (N2ICD) is sufficient to induce ADM in WT acinar cells. To directly investigate the relationship of the EGFR, Kras, and Notch signaling pathways in ADM, we examined the effect of Notch signaling in acinar cells harvested from EKO mice. Interestingly, these acinar cells fail to transdifferentiate in vitro upon transduction of N2ICD in 3D culture; however the transdifferentiation event can be rescued by co-expression of oncogenic Kras with N2ICD in acinar cells lacking EGFR. These results indicate that EGFR is important in Notch induced ADM, however there are other pathways that possibly can be utilized by acinar cells expressing oncogenic Kras to drive ADM. Citation Format: Christopher J. Halbrook, Howard C. Crawford. Redefining the role of Notch in acinar to ductal metaplasia. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A27.

Abstract Nearly all pancreatic ductal adenocarcinomas are caused by oncogenic mutations in the KRAS gene. Pharmacological inhibition of mutant KRAS has thus far been unsuccessful in the clinical setting, precipitating a need to understand the pathways downstream of KRAS which may prove more easily targeted with small molecule inhibitors. Here we show that PI3K p110α is absolutely required for pancreatic tumorigenesis while p110β is dispensable for this process. Surprisingly, ablation of p110α does not impair the ability of KRAS to activate AKT, demonstrating that AKT activation is not sufficient for transformation. Instead we find that p110α is required for robust activation of RAC1, a small GTPase required for pancreatic metaplasia. Consistent with this, our data show that p110α is necessary for regulating epithelial expression and activation of RAC-GEFs including Vav1, Tiam1 and Ect2. Ultimately, these results define the mechanistic role of p110α in pancreatic tumorigenesis and suggest selective inhibition of this PI3K isoform as a promising therapeutic approach to treating patients with pancreas cancer. Citation Format: Kenneth K. Takeuchi, Eileen Carpenter, Claire Wu, Christopher J. Halbrook, Richard Z. Lin, Howard C. Crawford. PI3K regulation of RAC1 is required for Kras-induced pancreatic tumorigenesis. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A04.

Abstract Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer related death in the United States. Roughly 45,000 patients are diagnosed with the disease each year and of these patients 94% will not survive past 5 years. The most common genetic alteration associated with PDAC is an oncogenic mutation in the KRAS gene, which is believed to initiate the disease. Mutant Kras is generally thought to signal constitutively to its downstream effector proteins, such as Raf/MEK/Erk and PI3K/AKT. However, recently we and others have demonstrated that Epidermal Growth Factor Receptor (EGFR) signaling upstream of mutant Kras is necessary for unlocking its oncogenic potential in the pancreas, distinct from Kras driven tumorigenesis in the lung or colon. Unfortunately, while EGFR inhibition is effective in blocking pancreatic tumorigenesis in mice, it has limited benefit in treating human PDAC patients. Furthermore, it has been shown that wild-type Nras and Hras have indispensable signaling roles in cells expressing oncogenic Kras, and that both the mutant and WT Ras signals are required for cell growth. Here we show that pancreatic cancer cell lines containing oncogenic Kras still require upstream signaling to maintain high levels of both active Erk and AKT although these signals are not necessarily EGFR derived. We have identified a subset of pancreatic cancer cell lines that rely upon IR/IGFR signaling to maintain the high levels of Erk and AKT signaling required for continued cell growth. Additionally, this signaling appears to be independent of oncogenic Kras and instead correlates with the levels of active wild-type Nras and Hras. This data indicates that patients may benefit from the simultaneous inhibition of both the EGFR and IR/IGFR signaling pathways. Citation Format: Kenneth K. Takeuchi, Howard C. Crawford. EGFR and IR/IGFR activation sustains ERK1/2 and AKT signaling independently of mutant Kras in pancreatic cancer cells lines. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B58. doi: 10.1158/1557-3125.RASONC14-B58

Abstract Mounting evidence indicates that oncogenic Ras can modulate cell autonomous inflammatory cytokine production, although the underlying mechanism remains unclear. Here we show that squamous cell carcinoma antigen (SCCA), a member of the Serpin family of serine/cysteine protease inhibitors, is transcriptionally up-regulated by oncogenic Ras via MAPK and the ETS family transcription factor PEA3. Increased SCCA expression leads to inhibition of protein turnover, unfolded protein response (UPR), activation of NF-κB, and is essential for Ras-mediated cytokine production and tumor growth. Analysis of human colorectal and pancreatic tumor samples reveals a positive correlation between Ras mutation, enhanced SCCA expression, and IL-6 expression. These results indicate that SCCA is a Ras-responsive factor that plays an essential role in Ras-associated cytokine production and tumorigenesis. Citation Format: Joseph Catanzaro, Namratha Sheshadri, Ji-An Pan, Yu Sun, Chanjuan Shi, Jinyu Li, Scott Powers, Howard Crawford, Wei-Xing Zong. Oncogenic Ras induces inflammatory cytokine production by upregulating squamous cell carcinoma antigen (SerpinB3). [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr A23. doi: 10.1158/1557-3125.RASONC14-A23