What's new in pancreatic cancer treatment pipeline?

NOSH-aspirin (NBS-1120) inhibits pancreatic cancer cell growth in a xenograft mouse model: Modulation of FoxM1, p53, NF-κB, iNOS, caspase-3 and ROS

Pancreatic cancer has poor survival rates and largely ineffective therapies. Aspirin is the prototypical anti-cancer agent but its long-term use is associated with significant side effects. NOSH-aspirin belongs to a new class of anti-inflammatory agents that were designed to be safer alternatives by releasing nitric oxide and hydrogen sulfide. In this study we evaluated the effects of NOSH-aspirin against pancreatic cancer using cell lines and a xenograft mouse model. NOSH-aspirin inhibited growth of MIA PaCa-2 and BxPC-3 pancreatic cancer cells with IC₅₀s of 47 ± 5, and 57 ± 4 nM, respectively, while it did not inhibit growth of a normal pancreatic epithelial cell line at these concentrations. NOSH-aspirin inhibited cell proliferation, caused G₀/G₁ phase cycle arrest, leading to increased apoptosis. Treated cells displayed increases in reactive oxygen species (ROS) and caspase-3 activity. In MIA PaCa-2 cell xenografts, NOSH-aspirin significantly reduced tumor growth and tumor mass. Growth inhibition was due to reduced proliferation (decreased PCNA expression) and induction of apoptosis (increased TUNEL positive cells). Expressions of ROS, iNOS, and mutated p53 were increased; while that of NF-κB and FoxM1 that were high in vehicle-treated xenografts were significantly inhibited by NOSH-aspirin. Taken together, these molecular events and signaling pathways contribute to NOSH-aspirin mediated growth inhibition and apoptotic death of pancreatic cancer cells in vitro and in vivo.

Inhibition of radiation-induced DNA repair and prosurvival pathways contributes to vorinostat-mediated radiosensitization of pancreatic cancer cells

OBJECTIVE

The intrinsic radioresistance of pancreatic cancer (PaCa) is caused by multiple oncogenic signaling pathways. In contrast to combining radiation therapy (RT) with targeted therapeutic agent(s) whose blockade can be circumvented by redundant signaling pathways, we evaluated the combination of RT with a broad-spectrum histone deacetylase inhibitor, vorinostat.

METHODS

Radiosensitization by vorinostat was analyzed using clonogenic survival assays. Apoptosis was evaluated using flow cytometry and immunoblotting. DNA repair was evaluated using immunofluorescence assessment of histone 2AX phosphorylation and immunoblotting for DNA repair proteins. Prosurvival pathway proteins were measured by immunoblotting and electrophoretic mobility shift assays.

RESULTS

Vorinostat significantly sensitized PaCa cells to radiation, but vorinostat-induced apoptosis did not contribute significantly to the observed radiosensitization. However, vorinostat inhibited DNA damage repair by targeting key DNA repair proteins and also abrogated prosurvival pathways responsible for PaCa aggressiveness and radioresistance. Specifically, the constitutively overexpressed epidermal growth factor receptor and nuclear factor κB pathways were shown to be induced by radiation and inhibited by vorinostat.

CONCLUSIONS

Vorinostat augments the antitumor effects of RT by abrogating radioresistance responses of PaCa cells mediated by prosurvival and DNA repair pathways and promises to be a clinically relevant adjunct to RT for treatment of PaCa.

Translational advances and novel therapies for pancreatic ductal adenocarcinoma: hope or hype?

Biological complexity, inaccessible anatomical location, nonspecific symptoms, lack of a screening biomarker, advanced disease at presentation and drug resistance epitomise pancreatic ductal adenocarcinoma (PDA) as a poor-prognosis, lethal disease. Twenty-five years of research (basic, translational and clinical) have barely made strides to improve survival, mainly because of a fundamental lack of knowledge of the biological processes initiating and propagating PDA. However, isolation of pancreas cancer stem cells or progenitors, whole-genome sequencing for driver mutations, advances in functional imaging, mechanistic dissection of the desmoplastic reaction and novel targeted therapies are likely to shed light on how best to treat PDA. Here we summarise current knowledge and areas where the field is advancing, and give our opinion on the research direction the field should be focusing on to better deliver promising therapies for our patients.

Selective cytotoxicity of Ponciri Fructus against glucose-deprived PANC-1 human pancreatic cancer cells via blocking activation of GRP78

Pancreatic cancer cells are sometimes exposed to stressful microenvironments such as glucose deprivation, hypoxia, and starvation of other nutrients. These stresses, which are characteristic of poorly vascularized solid tumors, activate the unfolded protein response (UPR). The UPR is a stress-signaling pathway present in tumor cells that is associated with molecular chaperone GRP78. Induction of GRP78 has been found to increase cell survival and decrease apoptotic potential through genetic alterations. Thus GRP78 may represent a novel target in the development of anticancer drugs. Here we established a novel screening program to identify chaperone modulators that exhibit preferential cytotoxic activity in glucose-deprived pancreatic cancer cells. During the course of our screening, we isolated an active substance, Ponciri Fructus (PF), from an herbal medicine source and identified it as a down-regulator of GRP78. As expected, PF inhibited expression of the GRP78 protein under glucose-deprivation conditions in a dose-dependent manner. Furthermore, it induced selective cytotoxicity against glucose-deprived cancer cells; this effect was not observed under normal growth conditions. We also detected apoptotic bodies on Hoechst staining and attempted to determine whether PF-induced apoptosis involved caspase-3 activation. Our results suggest that the GRP78-inhibitory action of PF was dependent on strict hypoglycemic conditions and that it resulted in the selective death of glucose-deprived pancreatic cancer cells.

Pancreatic cancer

The past two decades have witnessed an explosion in our understanding of pancreatic cancer, and it is now clear that pancreatic cancer is a disease of inherited (germ-line) and somatic gene mutations. The genes mutated in pancreatic cancer include KRAS2, p16/CDKN2A, TP53, and SMAD4/DPC4, and these are accompanied by a substantial compendium of genomic and transcriptomic alterations that facilitate cell cycle deregulation, cell survival, invasion, and metastases. Pancreatic cancers do not arise de novo, and three distinct precursor lesions have been identified. Experimental models of pancreatic cancer have been developed in genetically engineered mice, which recapitulate the multistep progression of the cognate human disease. Although the putative cell of origin for pancreatic cancer remains elusive, minor populations of cells with stem-like properties have been identified that appear responsible for tumor initiation, metastases, and resistance of pancreatic cancer to conventional therapies.

Pancreatic carcinogenesis

Pancreatic cancer is an almost universally lethal disease. Research over the last two decades has shown that pancreatic cancer is fundamentally a genetic disease, caused by inherited germline and acquired somatic mutations in cancer-associated genes. Multiple alterations in genes that are important in pancreatic cancer progression have been identified, including tumor suppressor genes, oncogenes, and genome maintenance genes. Furthermore, the identification of noninvasive precursor lesions of pancreatic adenocarcinoma has led to the formulation of a multi-step progression model of pancreatic cancer and the subsequent identification of early and late genetic alterations culminating in invasive cancer. In addition, an increased understanding of the molecular basis of the disease has facilitated the identification of new drug targets enabling rational drug design. The elucidation of genetic alterations in combination with the development of high-throughput sensitive techniques should lead to the discovery of effective biomarkers for early detection of this malignancy. This review focuses mainly on the current knowledge about the molecular insights of the pathogenesis of pancreatic ductal adenocarcinoma.

In vitro and in vivo comparison of DTPA- and DOTA-conjugated antiferritin monoclonal antibody for imaging and therapy of pancreatic cancer

Pancreatic cancer has a very poor prognosis with a less than 5% survival rate at 5 years. Neither external beam radiation nor chemotherapy, alone or in combination, have given encouraging results so far. A possible solution might come from the use of targeted therapy such as radioimmunotherapy. We present here the results obtained from the preclinical development of a new monoclonal antiferritin antibody (Ab), AMB8LK. Ferritin is overexpressed in pancreatic cancer and could thus be used as a target for the delivery of radioactivity at the tumour sites. The AMB8LK Ab was conjugated to three chelating agents: the 2-(4-isothiocyanatobenzyl)-diethylenetriamine pentaacetic acid (PSCN-Bz-DTPA), the (R)-2-amino-3-(4-isothiocyanatophenyl)propyl]-trans-(S,S)-cyclohexane-1,2-diamine-pentaacetic acid (p5CN-Bz-CHX-A"-DTPA) and the 2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid (pSCN-Bz-DOTA). Radiolabelling of the three immunoconjugates with indium 111 and yttrium 90 as well as in vitro stability and immunoreactivity against pure ferritin and cells expressing ferritin were analysed. In vivo biodistribution studies were conducted on normal and on human pancreatic adenocarcinoma CAPAN-1 tumour bearing mice. These experiments demonstrated good radiolabelling (>95%), stability and immunoreactivity of the three compounds. In the biodistribution studies, differences between the three immunoconjugates were apparent in the rate of blood clearance and in tumour, liver and bone uptake. A very good pancreatic adenocarcinoma tumour targeting was observed especially with the Bz-DTPA-AMB8LK: 20% of the injected dose of the indium-labelled compound 3 days after injection; 15% of the injected dose 5 days after that of the yttrium-labelled Ab. Altogether, these results in animal models suggest that (90)Y-Bz-DTPA-AMB8LK is a good candidate for further therapeutic efficacy studies.