Higher frequency of DPC4/Smad4 alterations in pancreatic cancer cell lines than in primary pancreatic adenocarcinomas

Differential Sensitivity to Ionizing Radiation in Gemcitabine-Resistant and Paclitaxel-Resistant Pancreatic Cancer Cells

PURPOSE

Chemoresistance remains a major challenge in treating pancreatic ductal adenocarcinoma (PDAC). Although chemoradiation has proven effective in other tumor types, such as head and neck squamous cell carcinoma, its role in PDAC and effect on acquired chemoresistance have yet to be fully explored. In this study, we investigated the sensitivity of gemcitabine-resistant (GR) and paclitaxel-resistant (PR) PDAC cells to ionizing radiation (IR) and their underlying mechanisms.

METHODS AND MATERIALS

GR and PR clones were generated from PANC-1, PATU-T, and SUIT2-007 pancreatic cancer cell lines. Cell survival after radiation was assessed using clonogenic assay, sulforhodamine B assay, apoptosis, and spheroid growth by bioluminescence. Radiation-induced DNA damage was assessed using Western blot, extra-long polymerase chain reaction, reactive oxygen species production, and immunofluorescence. Autophagy and modulation of the Hippo signaling pathway were investigated using proteomics, Western blot, immunofluorescence, and reverse-transcription quantitative polymerase chain reaction.

RESULTS

In both 2- and 3-dimensional settings, PR cells were more sensitive to IR and showed decreased β-globin amplification, indicating more DNA damage accumulation compared with GR or wild-type cells after 24 hours. Proteomic analysis of PR PATU-T cells revealed that the protein MST4, a kinase involved in autophagy and the Hippo signaling pathway, was highly downregulated. A differential association was found between autophagy and radiation treatment depending on the cell model. Interestingly, increased yes-associated protein nuclear localization and downstream Hippo signaling pathway target gene expression were observed in response to IR.

CONCLUSIONS

This was the first study investigating the potential of IR in targeting PDAC cells with acquired chemoresistance. Our results demonstrate that PR cells exhibit enhanced sensitivity to IR due to greater accumulation of DNA damage. Additionally, depending on the specific cellular context, radiation-induced modulation of autophagy and the Hippo signaling pathway emerged as potential underlying mechanisms, findings with potential to inform personalized treatment strategies for patients with acquired chemoresistance.

Inhibition of TGF-β signalling in combination with nal-IRI plus 5-Fluorouracil/Leucovorin suppresses invasion and prolongs survival in pancreatic tumour mouse models

Pancreatic ductal adenocarcinoma (PDAC) is one of the most aggressive malignancies. TGF-β is strongly expressed in both the epithelial and stromal compartments of PDAC, and dysregulation of TGF-β signalling is a frequent molecular disturbance in PDAC progression and metastasis. In this study, we investigated whether blockade of TGF-β signalling synergizes with nal-IRI/5-FU/LV, a chemotherapy regimen for malignant pancreatic cancer, in an orthotopic pancreatic tumour mouse model. Compared to nal-IRI/5-FU/LV treatment, combining nal-IRI/5-FU/LV with vactosertib, a TGF-β signalling inhibitor, significantly improved long-term survival rates and effectively suppressed invasion to surrounding tissues. Through RNA-sequencing analysis, we identified that the combination treatment results in robust abrogation of tumour-promoting gene signatures and positive enrichment of tumour-suppressing and apoptotic gene signatures. Particularly, the expression of tumour-suppressing gene Ccdc80 was induced by vactosertib and further induced by vactosertib in combination with nal-IRI/5-FU/LV. Ectopic expression of CCDC80 suppressed migration and colony formation concomitant with decreased expression of epithelial-to-mesenchymal transition (EMT) markers in pancreatic cancer cells. Collectively, these results indicate that combination treatment of vactosertib with nal-IRI/5-FU/LV improves overall survival rates in a mouse model of pancreatic cancer by suppressing invasion through CCDC80. Therefore, combination therapy of nal-IRI/5-FU/LV with vactosertib could provide clinical benefits to pancreatic cancer patients.

Dichotomous roles of TGF-β in human cancer

Transforming growth factor-β (TGF-β) mediates numerous biological processes, including embryonic development and the maintenance of cellular homeostasis in a context-dependent manner. Consistent with its central role in maintaining cellular homeostasis, inhibition of TGF-β signaling results in disruption of normal homeostatic processes and subsequent carcinogenesis, defining the TGF-β signaling pathway as a tumor suppressor. However, once carcinogenesis is initiated, the TGF-β signaling pathway promotes cancer progression. This dichotomous function of the TGF-β signaling pathway is mediated through altering effects on both the cancer cells, by inducing apoptosis and inhibiting proliferation, and the tumor microenvironment, by promoting angiogenesis and inhibiting immunosurveillance. Current studies support inhibition of TGF-β signaling either alone, or in conjunction with anti-angiogenic therapy or immunotherapy as a promising strategy for the treatment of human cancers.

Cancer Stem Cell and Gastrointestinal Cancer: Current Status, Targeted Therapy and Future Implications

The cancer stem cells (CSCs) are biologically distinct subset of rare cancer cells with inherent ability of self-renewal, de-differentiation, and capacity to initiate and maintain malignant tumor growth. Studies have further reported that CSCs prime cancer recurrence and therapy resistance. Therefore, targeting CSCs to inhibit cancer progression has become an attractive anti-cancer therapeutical strategy. Recent technical advances have provided a greater appreciation of the multistep nature of the oncogenesis and also clarified that CSC concept is not universally applicable. Irrespective, the role of the CSCs in gastrointestinal (GI) cancers, responsible for the most cancer-associated death, has been widely accepted and appreciated. However, despite the tremendous progress made in the last decade in developing markers to identify CSCs, and assays to assess tumorigenic function of CSCs, it remains an area of active investigation. In current article, we review findings related to the role and identification of CSCs in GI-cancers and discuss the crucial pathways involved in regulating CSCs populations’ development and drug resistance, and use of the tumoroid culture to test novel CSCs-targeted cancer therapies.

Comprehensive genomic analysis of a BRCA2 deficient human pancreatic cancer

Capan-1 is a well-characterised BRCA2-deficient human cell line isolated from a liver metastasis of a pancreatic adenocarcinoma. Here we report a genome-wide assessment of structural variations and high-depth exome characterization of single nucleotide variants and small insertion/deletions in Capan-1. To identify potential somatic and tumour-associated variations in the absence of a matched-normal cell line, we devised a novel method based on the analysis of HapMap samples. We demonstrate that Capan-1 has one of the most rearranged genomes sequenced to date. Furthermore, small insertions and deletions are detected more frequently in the context of short sequence repeats than in other genomes. We also identify a number of novel mutations that may represent genetic changes that have contributed to tumour progression. These data provide insight into the genomic effects of loss of BRCA2 function.

Inhibition of pancreatic carcinoma cell growth in vitro by DPC4 gene transfection

AIM: To detect the expression of DPC4 in malignant and non-malignant specimens of human pancreas, and observe the inhibition of retroviral pLXSN containing DPC4 on pancreatic carcinoma cells in vitro.

METHODS: The expression of DPC4 was determined in 40 pancreatic adenocarcinoma and 36 non-malignant pancreatic specimens by reverse-transcriptase polymerase chain reaction (RT-PCR) and immunohisto-chemistry. Furthermore, we constructed retroviral vectors containing DPC4, which then infected the pancreatic carcinoma cell line BxPC-3. Cell growth in vitro after being infected was observed, and the vascular endothelial growth factor (VEGF) mRNA level in the daughter cells was determined by semi-quantitative PCR assay.

RESULTS: The RT-PCR assay showed a positive rate of DPC4 mRNA in 100% (36/36) of normal specimens, compared to 40% (16/40) in adenocarcinoma specimens. The regional and intense positive cases of DPC4 expression in adenocarcinoma detected by immunohistochemistry were 10 and four, whereas it was all positive expression in normal tissues. There was a significant difference of DPC4 expression between them. The stable expression of DPC4 in the pancreatic carcinoma cells BxPC-3 could be resumed by retroviral vector pLXSN transfection, and could inhibit cell growth in vitro. Rather, DPC4 could decrease VEGF mRNA transcription levels.

CONCLUSION: The deletion of DPC4 expression in pancreatic carcinoma suggests that loss of DPC4 may be involved in the development of pancreatic carcinoma. The retroviral vector pLXSN containing DPC4 can inhibit the proliferation of pancreatic carcinoma cells, and down-regulate the level of VEGF.

The pathology of ductal-type pancreatic carcinomas and pancreatic intraepithelial neoplasia: insights for clinicians

The phenotypic classification of pancreatic neoplasms is based on their cellular lineage. Thus, tumors with a ductal, acinar, and endocrine phenotype can be distinguished. Most pancreatic neoplasms show a ductal phenotype and can be classified as ductal adenocarcinomas. Less common tumors with a ductal phenotype are the variants of ductal adenocarcinoma, intraductal papillary mucinous neoplasm (including colloid carcinoma), mucinous cystic neoplasm, medullary carcinoma, and other rare tumors. Ductal adenocarcinomas most likely develop from ductal proliferative lesions arising in the pancreatic duct system. A recently adopted classification system for these lesions distinguishes between three grades of pancreatic intraepithelial neoplasia (PanIN). Molecular studies have revealed that PanIN-2 and PanIN-3 lesions represent a distinct step toward invasive carcinoma.

Vascular endothelial growth factor-trap suppresses tumorigenicity of multiple pancreatic cancer cell lines

PURPOSE

Vascular endothelial growth factor A (VEGF-A) is a potent angiogenic agent that binds to two high affinity VEGF receptors (VEGFRs), a process facilitated by the low affinity neuropilin receptors. Although VEGF-A is overexpressed in pancreatic ductal adenocarcinoma, it is not known whether the in vivo growth of multiple pancreatic cancer cells can be efficiently blocked by VEGF-A sequestration.

EXPERIMENTAL DESIGN

Four human pancreatic cancer cell lines were grown s.c. in athymic nude mice. One cell line also was used to generate an orthotopic model of metastatic pancreatic cancer. The consequences of VEGF-A sequestration on tumor growth and metastasis were examined by injecting the mice with a soluble VEGFR chimer (VEGF-Trap) that binds VEGF-A with high affinity.

RESULTS

VEGF-Trap, initiated 2 days after tumor cell inoculation, suppressed the s.c. growth of four pancreatic cancer cell lines and markedly decreased tumor microvessel density. Analysis of RNA from tumors generated with T3M4 cells revealed that VEGF-Trap decreased the expression of VEGFR-1 and neuropilin-1 and -2. VEGF-Trap, initiated 3 weeks after tumor implantation, also attenuated intrapancreatic tumor growth and metastasis in an orthotopic model using PANC-1 cells.

CONCLUSIONS

VEGF-Trap is a potent suppressor of pancreatic tumor growth and metastasis and also may act to attenuate neuropilin-1 and -2 and VEGFR-1 expression. Therefore, VEGF-Trap may represent an exceedingly useful therapeutic modality for pancreatic ductal adenocarcinoma.

TGFbeta1 signaling via alphaVbeta6 integrin

BACKGROUND

Transforming growth factor beta1 (TGFbeta1) is a potent inhibitor of epithelial cell growth, thus playing an important role in tissue homeostasis. Most carcinoma cells exhibit a reduced sensitivity for TGFbeta1 mediated growth inhibition, suggesting TGFbeta1 participation in the development of these cancers. The tumor suppressor gene DPC4/SMAD4, which is frequently inactivated in carcinoma cells, has been described as a key player in TGFbeta1 mediated growth inhibition. However, some carcinoma cells lacking functional SMAD4 are sensitive to TGFbeta1 induced growth inhibition, thus requiring a SMAD4 independent TGFbeta1 pathway.

RESULTS

Here we report that mature TGFbeta1 is a ligand for the integrin alphaVbeta6, independent of the common integrin binding sequence motif RGD. After TGFbeta1 binds to alphaVbeta6 integrin, different signaling proteins are activated in TGFbeta1-sensitive carcinoma cells, but not in cells that are insensitive to TGFbeta1. Among others, interaction of TGFbeta1 with the alphaVbeta6 integrin resulted in an upregulation of the cell cycle inhibitors p21/WAF1 and p27 leading to growth inhibition in SMAD4 deleted as well as in SMAD4 wildtype carcinoma cells.

CONCLUSIONS

Our data provide support for the existence of an alternate TGFbeta1 signaling pathway that is independent of the known SMAD pathway. This alternate pathway involves alphaVbeta6 integrin and the Ras/MAP kinase pathway and does not employ an RGD motif in TGFbeta1-sensitive tumor cells. The combined action of these two pathways seems to be necessary to elicit a complete TGFbeta1 signal.

DPC-4 (Smad-4) and K-ras gene mutations in biliary tract epithelium in children with anomalous pancreaticobiliary ductal union

BACKGROUND/PURPOSE

Recent studies have found that anomalous pancreaticobiliary ductal union (APBDU) is a substantial risk factor for biliary tract cancer at a younger age. DPC-4 (Smad-4) is a new tumor suppressor gene frequently inactivated in pancreatic and bile duct adenocarcinoma. To clarify carcinogenesis in APBDU, the authors investigated possible DPC-4 and K-ras mutations in 35 pediatric patients.

METHODS

DNA was extracted from biliary tract epithelial cells, which were resected surgically and histologically purified using microdissection. Polymerase chain reaction (PCR) primers were designed specifically for exons 8-11 of DPC-4 (18q21.1) and exons 1-2 of the K-ras oncogene (12p12.1). DNA sequences were determined using the direct DyeDeoxy Terminator Cycle method.

RESULTS

Of 35 children, 30 had wild-type DPC-4 and K-ras genes. K-ras mutations were detected in 5 patients, 4 of whom showed epithelial hyperplasia or metaplasia. In a 12-year-old girl with adenocarcinoma arising from a choledochal cyst, K-ras and DPC-4 (homozygous deletion) mutations were identified simultaneously.

CONCLUSIONS

These results suggest that carcinogenesis in the biliary tract epithelium in APBDU is accompanied by multistep genetic mutational events; K-ras gene mutation occurs early in epithelial hyperplasia or metaplasia, whereas inactivation of the DPC-4 gene accumulates late in the progression of biliary tract adenocarcinoma.

Tumor-suppressing pathways in cystic pancreatic tumors

INTRODUCTION AND AIMS

Serous and mucinous cystic pancreatic tumors have different clinical behavior. We evaluated whether they also have genotypic differences by analyses of the tumor suppressor genes, p16INK4a, p53, and DPC4.

METHODOLOGY

Seven serous cystadenomas (SCA) and seven malignant mucinous cystadenocarcinomas (MCC) were analyzed for alterations in the tumor suppressor genes p16INK4a, p53, and DPC4 by single-strand conformational variant analysis, direct sequencing, and immunohistochemical analysis. Methylation-specific polymerase chain reaction analysis was performed to identify p16INK4a promoter hypermethylation. Clinical data were compared with genetic data.

RESULTS

None of the seven patients with SCAs but five of the seven patients with MCCs died of the tumor after a median follow-up of 44.5 months (range, 4-169 months). All seven MCCs had alterations in at least one tumor suppressor gene compared with none of the seven SCAs. Of the seven MCCs, three had inactivating p16INK4a promoter hypermethylation, five had p53 alterations, and three had DPC4 mutations.

CONCLUSIONS

The tumor suppressor genes p16INK4a, p53, and appear to play an important role in the tumorigenesis of MCCs but not SCAs. These molecular data underscore the clinical and histologic differences of serous and mucinous cystic pancreatic tumors.

Detection of oncogenes in chronic pancreatitis

BACKGROUND

The pathogenesis of chronic pancreatitis (CP) remains poorly understood. Recently, molecular biology has identified the genetic background for many patients with hereditary CP. In addition, a number of studies have focused on the detection of proto-oncogenes and tumour suppressor gene mutations in the pathogenesis of CP. So far, the use of these mutations (with the exception of mutations causing hereditary CP), as diagnostic and prognostic markers is still controversial.

DISCUSSION

It is well known that the risk of pancreatic cancer in patients with CP, especially the hereditary form, is high. At present, there is insufficient evidence to show a clear relationship between the development of pancreatic cancer and certain mutations. New biotechnological methods, such as DNA array expression analysis, expand our knowledge of the molecular pathogenesis of this disease and may help to develop specific diagnostic, prognostic and therapeutic tools. However, until long-term studies examine the safety and efficacy of certain genetic markers, long-term follow-up of patients with CP who harbour mutations is needed.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.

Role of transforming growth factor beta in cancer

Transforming growth factor beta (TGF-beta) is an effective and ubiquitous mediator of cell growth. The significance of this cytokine in cancer susceptibility, cancer development and progression has become apparent over the past few years. TGF-beta plays various roles in the process of malignant progression. It is a potent inhibitor of normal stromal, hematopoietic, and epithelial cell growth. However, at some point during cancer development the majority of transformed cells become either partly or completely resistant to TGF-beta growth inhibition. There is growing evidence that in the later stages of cancer development TGF-beta is actively secreted by tumor cells and not merely acts as a bystander but rather contributes to cell growth, invasion, and metastasis and decreases host-tumor immune responses. Subtle alteration of TGF-beta signaling may also contribute to the development of cancer. These various effects are tissue and tumor dependent. Identifying and understanding TGF-beta signaling pathway abnormalities in various malignancies is a promising avenue of study that may yield new modalities to both prevent and treat cancer. The nature, prevalence, and significance of TGF-beta signaling pathway alterations in various forms of human cancer as well as potential preventive and therapeutic interventions are discussed in this review.

Pancreatic tumours: molecular pathways implicated in ductal cancer are involved in ampullary but not in exocrine nonductal or endocrine tumorigenesis

Alterations of K- ras, p53, p16 and DPC4/Smad4 characterize pancreatic ductal cancer (PDC). Reports of inactivation of these latter two genes in pancreatic endocrine tumours (PET) suggest that common molecular pathways are involved in the tumorigenesis of pancreatic exocrine and endocrine epithelia. We characterized 112 primary pancreatic tumours for alterations in p16 and DPC4 and immunohistochemical expression of DPC4. The cases included 34 PDC, 10 intraductal papillary-mucinous tumours (IPMT), 6 acinar carcinomas (PAC), 5 solid-pseudopapillary tumours (SPT), 16 ampulla of Vater cancers (AVC) and 41 PET. All tumours were also presently or previously analysed for K- ras and p53 mutations and allelic loss at 9p, 17p and 18q. Alterations in K- ras, p53, p16 and DPC4 were found in 82%, 53%, 38% and 9% of PDC, respectively and in 47%, 60%, 25% and 6% of AVC. Alterations in these genes were virtually absent in PET, PAC or SPT, while in IPMT only K- ras mutations were present (30%). Positive immunostaining confirmed the absence of DPC4 alterations in all IPMT, SPT, PAC and PET, while 47% of PDC and 38% of AVC were immunonegative. These data suggest that pancreatic exocrine and endocrine tumourigenesis involves different genetic targets and that among exocrine pancreatic neoplasms, only ductal and ampullary cancers share common molecular events.

Multiple primary tumors as an indicator for p16INK4a germline mutations in pancreatic cancer patients?

Multiple primary tumors in pancreatic cancer patients might indicate a genetic predisposition to the development of malignancies. In this study we evaluated whether the mutation rate of the TP53 and p16INK4a genes of pancreatic cancers differs in pancreatic cancer patients with and without multiple primaries. Furthermore, we investigated whether pancreatic cancer patients with multiple primaries carry germline mutations in either p16INK4a, TP53, or BRCA2 tumor suppressor genes to detect a genetic alteration that predisposes to the development of different primaries. Fourteen (23%) of 60 pancreatic cancer patients developed histologically verified additional primaries during their lifetimes. Normal constitutional and tumor DNA of the 14 patients with a positive cancer history, but negative family history, were analyzed for p16INK4a, TP53, and BRCA2 mutations by single-strand conformational variant (SSCV) analysis and direct sequencing. Hypermethylation of the p16INK4a promoter region in pancreatic cancers was identified by methylation-specific polymerase chain reaction (PCR; MSP). Four of 14 pancreatic carcinomas carried somatic intragenic p16INK4a mutations, and another four tumors revealed hypermethylation of the p16INK4a promoter region. Somatic intragenic TP53 mutations were identified in six of 14 tumors. None of the pancreatic cancer patients carried TP53 or BRCA2 germline mutations. In contrast, one of 14 pancreatic cancer patients with multiple primaries carried the p16INK4a mutation A68V in his germline. This mutation was localized in the conserved second ankyrin repeat of p16INK4a and did not occur in 100 control patients. The frequency of somatic TP53 and p16INK4a mutations in pancreatic cancer is similar in patients with and without multiple primaries. TP53 and BRCA2 germline mutations seem not to be significantly associated with the occurrence of multiple primaries in pancreatic cancer patients. However, p16INK4a germline mutations might be causative for tumor development in some pancreatic cancer patients with multiple primaries. The genetic investigation of patients with accumulation of different cancers even without a positive family history may be a new approach for the understanding of the relation of different cancers.

Loss of Dpc4 expression in colonic adenocarcinomas correlates with the presence of metastatic disease

DPC4 is a candidate tumor suppressor gene on chromosome 18q21, a region that shows high frequencies of allelic losses in pancreatic and colorectal adenocarcinomas. Biallelic inactivation of DPC4 has been reported in half of pancreatic cancers, but are relatively infrequent in other tumor types. The role of DPC4 inactivation in colorectal neoplasms has not been fully characterized. An immunohistochemical assay for Dpc4 protein expression has been recently developed and shown to be a sensitive and specific surrogate for alterations in the DPC4 gene. In this study we examined the expression of Dpc4 protein in formalin-fixed archival tissue from 83 colorectal lesions, including 19 adenomas and 64 sporadic adenocarcinomas (11 stage I, 13 stage II, 17 stage III, and 23 stage IV cancers). None of the adenomas or stage I adenocarcinomas showed loss of Dpc4 expression, whereas one of 13 (8%) stage II, one of 17 (6%) stage III, and five of 23 (22%) of stage IV cancers showed loss of Dpc4 expression. There was a borderline significant difference in loss of Dpc4 reactivity in colorectal tumors with distant metastasis at presentation (22%) versus primary tumors without distant metastasis (5%) (Fisher's exact test, P = 0.05; chi(2) = 0.04). Poorly differentiated histology or status of pericolonic lymph nodes did not affect Dpc4 expression. Alterations in DPC4 are involved in the progression of a subset of colorectal carcinomas, especially those that present with advanced disease. In the sequential pathogenesis of colorectal tumors, inactivation of DPC4 is likely to be a late event.