Enhancement of Gemcitabine-Induced Apoptosis by Restoration of p53 Function in Human Pancreatic Tumors

Association of MDM2 expression with shorter progression-free survival and overall survival in patients with advanced pancreatic cancer treated with gemcitabine-based chemotherapy

This study evaluated the prognostic roles of murine double minute 2 (MDM2) and p53 in pancreatic cancer patients treated with gemcitabine-based chemotherapy. A total of 137 advanced or recurrent adenocarcinoma patients who were treated with gemcitabine-based palliative chemotherapy were reviewed, selected from 957 patients with pancreatic malignancy between 2008 and 2013 at our hospital. Immunohistochemical staining for MDM2 and p53 with formalin-fixed, paraffin-embedded tumor tissues was independently reviewed. Nuclear or cytoplasmic expression of MDM2 and p53 was found in tumor cells of 30 (21.9%) and 71 (51.8%) patients, respectively. Patients with MDM2 expression had shorter median overall survival (OS) (3.7 vs 5.8 mo; P = .048) and median progression-free survival (PFS) (1.5 vs 2.5 mo; P < .001); by contrast, p53 expression was not correlated with OS or PFS. In the multivariate analysis, MDM2 expression (hazard ratio = 1.731; P = .025) was an independent and unfavorable prognostic factor of OS. Additionally, MDM2 expression was significantly associated with progressive disease (PD) and death (P = .015) following first-line gemcitabine-based therapy. In advanced pancreatic cancer patients, MDM2 expression is associated with shorter OS and PFS after gemcitabine-based chemotherapy.

Mutant p53 stimulates chemoresistance of pancreatic adenocarcinoma cells to gemcitabine

Pancreatic adenocarcinoma (PDAC) is the fourth leading cause of cancer-related deaths worldwide; PDAC is characterized by poor prognosis, resistance to conventional chemotherapy and high mortality rate. TP53 tumor suppressor gene is frequently mutated in PDAC, resulting in the accumulation of mutated protein with potential gain-of-function (GOF) activities, such as genomic instability, hyperproliferation and chemoresistance. The purpose of this study was to assess the relevance of the p53 status on the PDAC cells response to the standard drug gemcitabine. We also examined the potential therapeutic effect of p53-reactivating molecules to restore the mutant p53 function in GEM treated PDAC cells. We showed that gemcitabine stabilized mutant p53 protein in the nuclei and induced chemoresistance, concurrent with the mutant p53-dependent expression of Cdk1 and CCNB1 genes, resulting in a hyperproliferation effect. Despite the adverse activation of mutant p53 by gemcitabine, simultaneous treatment of PDAC cells with gemcitabine and p53-reactivating molecules (CP-31398 and RITA) reduced growth rate and induced apoptosis. This synergistic effect was observed in both wild-type and mutant p53 cell lines and was absent in p53-null cells. The combination drug treatment induced p53 phosphorylation on Ser15, apoptosis and autophagosome formation. Furthermore, pharmacological inhibition of autophagy further increased apoptosis stimulated by gemcitabine/CP-31398 treatment. Together, our results show that gemcitabine aberrantly stimulates mutant p53 activity in PDAC cells identifying key processes with potential for therapeutic targeting. Our data also support an anti-tumoral strategy based on inhibition of autophagy combined with p53 activation and standard chemotherapy for both wild-type and mutant p53 expressing PDACs.

Tanshinone IIA inhibits viral oncogene expression leading to apoptosis and inhibition of cervical cancer

Human papilloma virus (HPV) is the well-established etiological factor of cervical cancer. E6 and E7 oncoproteins expressed by HPV are known to inactivate tumor suppressor proteins p53 and pRb, respectively. Tanshinone IIA (Tan IIA) is a diterpenoid naphthoquinone found in the traditional Chinese medicine Danshen (Salvia sp.). Tan IIA has been shown to possess anti-tumor activity against several cancer types. In this study we show that Tan IIA potently inhibited proliferation of the human cervical cancer CaSki, SiHa, HeLa and C33a cells. Mechanistically in HPV positive CaSki cells, Tan IIA was found to (i) downregulate expression of HPV E6 and E7 genes and modulate associated proteins E6AP and E2F1, (ii) cause S phase cell cycle arrest, (iii) induce accumulation of p53 and alter expression of p53-dependent targets, (iv) modulate pRb and related proteins, and (v) cause p53-mediated apoptosis by moderating Bcl2, Bax, caspase-3, and PARP cleavage expressions. In vivo, Tan IIA resulted in over 66% reduction in tumor volume of cervical cancer xenograft in athymic nude mice. Tan IIA treated tumor tissues had lower expression of proliferation marker PCNA and changes in apoptosis targets were in agreement with in vitro studies, further confirming reduced proliferation and involvement of multiple targets behind anti-cancer effects. This is the first demonstration of Tan IIA to possess significant anti-viral activity by repressing HPV oncogenes leading to inhibition of cervical cancer. Together, our data suggest that Tan IIA can be exploited as a potent therapeutic agent for the prevention and treatment of cervical and other HPV-related cancers.

Intratumoral Mistletoe (Viscum album L) Therapy in Patients With Unresectable Pancreas Carcinoma: A Retrospective Analysis

Pancreatic carcinoma remains one of the main causes for cancer-related death. Intratumoral application of anticancer agents is discussed as a promising method for solid tumors such as pancreatic cancer. Endoscopic ultrasound provides a good tool to examine and treat the pancreas. European mistletoe (Viscum album L) is a phytotherapeutic commonly used in integrative oncology in Central Europe. Its complementary use seeks to induce immunostimulation and antitumoral effects as well as alleviate chemotherapeutic side effects. Intratumoral mistletoe application has induced local tumor response in various cancer entities. This off-label use needs to be validated carefully in terms of safety and benefits. Here we report on 39 patients with advanced, inoperable pancreatic cancer, who received in total 223 intratumoral applications of mistletoe, endoscopic ultrasound guided or under transabdominal ultrasound control. No severe procedure-related events were reported. Adverse drug reactions were mainly increased body temperature or fever in 14% and 11% of the applications, respectively. Other adverse drug reactions, such as pain or nausea, occurred in less than 7% of the procedures. No severe adverse drug reaction was recorded. Patients received standard first- and second-line chemotherapy and underwent adequate palliative surgical interventions as well as additive subcutaneous and partly intravenous mistletoe application. A median survival of 11 months was observed for all patients, or 11.8 and 8.3 months for stages III and IV, respectively. Due to the multimodal therapeutic setting and the lack of a control group, the effect of intratumoral mistletoe administration alone remains unclear. This retrospective analysis suggests that intratumoral-applicated mistletoe might contribute to improve survival of patients with pancreatic cancer. In conclusion, the application is feasible and safe, and its efficacy should be evaluated in a randomized controlled trial.

Concentrative nucleoside transporter 1 (hCNT1) promotes phenotypic changes relevant to tumor biology in a translocation-independent manner

Nucleoside transporters (NTs) mediate the uptake of nucleosides and nucleobases across the plasma membrane, mostly for salvage purposes. The canonical NTs belong to two gene families, SLC29 and SLC28. The former encode equilibrative nucleoside transporter proteins (ENTs), which mediate the facilitative diffusion of natural nucleosides with broad selectivity, whereas the latter encode concentrative nucleoside transporters (CNTs), which are sodium-coupled and show high affinity for substrates with variable selectivity. These proteins are expressed in most cell types, exhibiting apparent functional redundancy. This might indicate that CNTs have specific roles in the physiology of the cell beyond nucleoside salvage. Here, we addressed this possibility using adenoviral vectors to restore tumor cell expression of hCNT1 or a polymorphic variant (hCNT1S546P) lacking nucleoside translocation ability. We found that hCNT1 restoration in pancreatic cancer cells significantly altered cell-cycle progression and phosphorylation status of key signal-transducing kinases, promoted poly-(ADP-ribose) polymerase hyperactivation and cell death and reduced cell migration. Importantly, the translocation-defective transporter triggered these same effects on cell physiology. Moreover, this study also shows that restoration of hCNT1 expression is able to reduce tumor growth in a mouse model of pancreatic adenocarcinoma. These data predict a novel role for a NT protein, hCNT1, which appears to be independent of its role as mediator of nucleoside uptake by cells. Thereby, hCNT1 fits the profile of a transceptor in a substrate translocation-independent manner and is likely to be relevant to tumor biology.

The proline TP53 variant stimulates likely lymphangiogenesis in an orthotopic mouse model of pancreatic cancer

Background:

Pancreatic cancer is a deadly disease characterised by high incidence of TP53 mutations. Restoration of TP53 function is perceived as a highly attractive therapeutic strategy, whose effects are not well characterised.

Methods:

The current work adapted an inducible strategy of stage-specific reexpression of wild-type (wt) TP53 in an in vivo orthotopic mouse model of pancreatic cancer.

Results:

The reconstitution of wt TP53 function in TP53-mutant DanG and MiaPaCa-2 cells caused G1 cell cycle arrest but no evidence of apoptosis induction. Consistent with subcutaneous xenograft models, we found that wt TP53 reduced primary tumour growth. Wt TP53 reexpression during early tumour growth led to significant increase in vascularisation. This correlated with an unexpectedly high rate of micro-metastases in lymph nodes of animals with wt TP53 induction, despite the 90% decrease in median primary tumour weight. Reexpression of wt TP53 later in tumour development did not significantly affect the number of CD31-reactive vessels, but increased lymphatic vessel density.

Conclusion:

The increased number of lymphatic vessels and micro-metastases suggests that wt TP53 induction complexly affected the biology of different tumour constituents of pancreatic cancer. Our observation suggests that combination of the inducible system with an orthotopic model can yield important insights into in vivo pancreatic cancer biology.

Connexin-26 is a key factor mediating gemcitabine bystander effect

Gemcitabine is a nucleoside analogue with anticancer activity. Inside the cell, it is sequentially phosphorylated to generate the active drug. Phosphorylated nucleoside analogues have been shown to traffic through gap junctions. We investigated the participation of gap junctional intercellular communication (GJIC) as a possible mechanism spreading gemcitabine cytotoxicity in pancreatic tumors. Immunohistochemical analysis of pancreatic cancer biopsies revealed increased connexin 26 (Cx26) content but loss of connexins 32 (Cx32) and 43 (Cx43) expression. Cx26 abundance in neoplastic areas was confirmed by Cx26 mRNA in situ hybridization. Heterogeneity on the expression levels and the localization of Cx26, Cx32, and Cx43 were identified in pancreatic cancer cells and found to be associated with the extent of GJIC, and correlated with gemcitabine bystander cytotoxic effect. The abundance of Cx26 at the contact points in tumoral regions prompted us to study the involvement of Cx26 in the GJIC of gemcitabine toxic metabolites and their influence on the antitumoral effects of gemcitabine. Knockdown of Cx26 led to decreased GJIC and reduced gemcitabine bystander killing whereas overexpression of Cx26 triggered increased GJIC and enhanced the gemcitabine cytotoxic bystander effect. Gemcitabine treatment of mice bearing tumors, with a high GJIC capacity, resulted in a significant delay in tumor progression. Interestingly, gemcitabine administration in mice bearing tumors that overexpress Cx26 triggered a dramatic tumor regression of 50% from the initial volume. This study shows that Cx26 participates in the gap junction-mediated bystander cytoxic effect of gemcitabine and provides evidence that upregulation of Cx26 improves gemcitabine anticancer efficacy.

Rationale for possible targeting of histone deacetylase signaling in cancer diseases with a special reference to pancreatic cancer

There is ongoing interest to identify signaling pathways and genes that play a key role in carcinogenesis and the development of resistance to antitumoral drugs. Given that histone deacetylases (HDACs) interact with various partners through complex molecular mechanims leading to the control of gene expression, they have captured the attention of a large number of researchers. As a family of transcriptional corepressors, they have emerged as important regulators of cell differentiation, cell cycle progression, and apoptosis. Several HDAC inhibitors (HDACis) have been shown to efficiently protect against the growth of tumor cells in vitro as well as in vivo. The pancreatic cancer which represents one of the most aggressive cancer still suffers from inefficient therapy. Recent data, although using in vitro tumor cell cultures and in vivo chimeric mouse model, have shown that some of the HDACi do express antipancreatic tumor activity. This provides hope that some of the HDACi could be potential efficient anti-pancreatic cancer drugs. The purpose of this review is to analyze some of the current data of HDACi as possible targets of drug development and to provide some insight into the current problems with pancreatic cancer and points of interest for further study of HDACi as potential molecules for pancreatic cancer adjuvant therapy.

Paclitaxel alters the expression and specific activity of deoxycytidine kinase and cytidine deaminase in non-small cell lung cancer cell lines

Background

We observed that paclitaxel altered the pharmacokinetic properties of gemcitabine in patients with non-small cell lung cancer (NSCLC) and limited the accumulation of gemcitabine and its metabolites in various primary and immortalized human cells. Therefore, we classified the drug-drug interaction and the effects of paclitaxel on deoxycytidine kinase (dCK) and cytidine deaminase (CDA) in three NSCLC cell lines. These enzymes are responsible for the metabolism of gemcitabine to its deaminated metabolite dFdU (80% of the parent drug) and the phosphorylated metabolites dFdCMP, dFdCDP and dFdCTP. These metabolites appear to relate to sensitivity and tolerability of gemcitabine based on previous animal and laboratory studies.

Methods

Three immortalized human cells representative of the most common histological subtypes identified in patients with advanced NSCLC were exposed to the individual drugs or combinations to complete a multiple drug effect analysis. These same cell lines were exposed to vehicle-control or paclitaxel and the mRNA levels, protein expression and specific activity of dCK and CDA were compared. Comparisons were made using a two-tailed paired t-test or analysis of variance with a P value of < 0.05 considered significant.

Results

The multiple drug effect analysis indicated synergy for H460, H520 and H838 cells independent of sequence. As anticipated, paclitaxel-gemcitabine increased the number of G2/M cells, whereas gemcitabine-paclitaxel increased the number of G0/G1 or S cells. Paclitaxel significantly decreased dCK and CDA mRNA levels in H460 and H520 cells (40% to 60%, P < 0.05) and lowered dCK protein (24% to 56%, P < 0.05) without affecting CDA protein. However, paclitaxel increased both dCK (10% to 50%) and CDA (75% to 153%) activity (P < 0.05). Paclitaxel caused substantial declines in the accumulation of the deaminated and phosphorylated metabolites in H520 cells (P < 0.05); the metabolites were not measurable in the remaining two cell lines. The ratio of dCK to CDA mRNA levels corresponded to the combination index (CI) estimated for sequential paclitaxel-gemcitabine.

Conclusion

In summary, paclitaxel altered the mRNA levels and specific activity of dCK and CDA and these effects could be dependent on histological subtype. More cell and animal studies are needed to further characterize the relationship between mRNA levels and the overall drug-drug interaction and the potential to use histological subtype as a predictive factor in the selection of an appropriate anticancer drug regimen.

Inducing apoptosis and enhancing chemosensitivity to gemcitabine via RNA interference targeting Mcl-1 gene in pancreatic carcinoma cell

PURPOSE

Resistance to chemotherapy is a major cause of treatment failure and poor prognosis in pancreatic carcinoma. Myeloid cell leukemia-1 (Mcl-1) is highly up-regulated in pancreatic carcinoma and is associated with the anti-apoptosis and the resistance to chemotherapy drugs. Suppression of Mcl-1 would be an approach to induce apoptosis and enhance the chemosensitivity.

METHODS

In this study, three pancreatic cancer cell lines (PANC-1, BxPC-3 and SW1900) stably expressing shRNAs targeting Mcl-1 gene were established and gene expression inhibition was assessed by Real-Time QPCR and Western blotting. The effects of Mcl-1 downregulation mediated by RNAi were explored in vitro and in vivo.

RESULTS

We showed that the specific downregulation of Mcl-1 strikingly inhibited cell growth, colony formation, cell cycle arrest and induced apoptosis in pancreatic cancer cells in vitro, and markedly decreased the tumorigenicity in a mouse xenograft model. Moreover, knockdown of Mcl-1 significantly increased the chemosensitivity to Gemcitabine in pancreatic carcinoma cells.

CONCLUSIONS

Our data suggests that the specific downregulation of Mcl-1 by RNAi is a promising approach to induce apoptosis and enhance the chemosensitivity for pancreatic carcinoma gene therapy.

A novel alkylating agent, glufosfamide, enhances the activity of gemcitabine in vitro and in vivo

Glufosfamide is an alkylating agent consisting of iphosphoramide mustard conjugated to glucose that is currently included in clinical studies of pancreatic cancer. We studied the effects of glufosfamide, in combination with gemcitabine, on in vitro and in vivo models of pancreatic cancer. In proliferation assays, glufosfamide and gemcitabine inhibited the growth of MiaPaCa-2, H766t, and PANC-1 cells, but the combination of the two agents provided greater effects. Apoptosis of MiaPaCa-2 cells, measured by fluorescence-activated cell sorting, was enhanced by the combination of the two drugs, compared to single-agent treatment. Glufosfamide alone inhibited the growth of red fluorescent protein-expressing MiaPaCa-2 tumors in an orthotopic nude mouse model in a dose-dependent manner. Combining glufosfamide (30 mg/kg) with gemcitabine resulted in enhanced inhibition of tumor growth and significantly prolonged survival. Immunohistochemistry of excised tumors revealed that both glufosfamide and gemcitabine increased levels of apoptosis (measured by terminal deoxynucleotidyl transferase-mediated nick end labeling staining) and reduced proliferation (measured by proliferating cell nuclear antigen staining). No effects on microvessel density were observed. These results support the use of the alkylating agent glufosfamide and the DNA synthesis inhibitor gemcitabine, rather than the use of either agent alone, to provide greater benefits and demonstrate that this combination treatment should be useful in the clinical treatment of pancreatic carcinoma.

Synergistic inhibition of pancreatic adenocarcinoma cell growth by trichostatin A and gemcitabine

We investigated the ability of the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) to interact with gemcitabine (GEM) in inducing pancreatic cancer cell death. The combined treatment with TSA and GEM synergistically inhibited growth of four pancreatic adenocarcinoma cell lines and induced apoptosis. This effect was associated with the induction of reactive oxygen species (ROS) by GEM, increased expression of the pro-apoptotic BIM gene by both TSA and GEM and downregulation of the 5'-nucleotidase UMPH type II gene by TSA. The expression of other genes critical for GEM resistance (nucleoside transporters, deoxycytidine kinase, cytidine deaminase, and ribonucleotide reductase genes) was not affected by TSA. The functional role of ROS in cell growth inhibition by GEM was supported by (i) a significantly reduced GEM-associated growth inhibition by the free radical scavenger N-acetyl-L-cysteine, and (ii) a positive correlation between the basal level of ROS and sensitivity to GEM in 10 pancreatic cancer cell lines. The functional role of both Bim and 5'-nucleotidase UMPH type II in cell growth inhibition by TSA and GEM was assessed by RNA interference assays. In vivo studies on xenografts of pancreatic adenocarcinoma cells in nude mice showed that the association of TSA and GEM reduced to 50% the tumour mass and did not cause any apparent form of toxicity, while treatments with TSA or GEM alone were ineffective. In conclusion, the present study demonstrates a potent anti-tumour activity of TSA/GEM combination against pancreatic cancer cells in vitro and in vivo, strongly supporting the use of GEM in combination with an HDAC inhibitor for pancreatic cancer therapy.