Phase II evaluation of continuous-infusion 5-fluorouracil, leucovorin, mitomycin-C, and oral dipyridamole in advanced measurable pancreatic cancer: a North Central Cancer Treatment Group Trial

Molecular classification as prognostic factor and guide for treatment decision of pancreatic cancer

Clinico-pathological factors fail to consistently predict the outcome after pancreatic resection for pancreatic ductal adenocarcinoma (PDAC). PDACs show a high level of inter- and intra- tumor genetic heterogeneity. A molecular classification should help sort patients into less heterogeneous and more appropriate groups regarding the metastatic risk and the therapeutic response, with the consequences of better predicting evolution and better orienting the treatment. PDAC can be classified based on mutational subtypes and 18gene alterations. Whole-genome sequencing identified mutational signatures, mutational burden and hyper-mutated tumors with specific DNA repair defects. Their overlap/similarities allow the definition of molecular subtypes. DNA and RNA classifications can be used in prognosis assessment. They are useful in therapeutic choice for they allow the design of approaches that can predict the respective drug sensitivity of each molecular subtype. This review provides a comprehensive analysis of available molecular classifications in PDAC and how this can help guide clinical decisions.

Immediate utility of two approved agents to target both the metabolic mevalonate pathway and its restorative feedback loop

New therapies are urgently needed for hematologic malignancies, especially in patients with relapsed acute myelogenous leukemia (AML) and multiple myeloma. We and others have previously shown that FDA-approved statins, which are used to control hypercholesterolemia and target the mevalonate pathway (MVA), can trigger tumor-selective apoptosis. Our goal was to identify other FDA-approved drugs that synergize with statins to further enhance the anticancer activity of statins in vivo. Using a screen composed of other FDA approved drugs, we identified dipyridamole, used for the prevention of cerebral ischemia, as a potentiator of statin anticancer activity. The statin-dipyridamole combination was synergistic and induced apoptosis in multiple myeloma and AML cell lines and primary patient samples, whereas normal peripheral blood mononuclear cells were not affected. This novel combination also decreased tumor growth in vivo. Statins block HMG-CoA reductase (HMGCR), the rate-limiting enzyme of the MVA pathway. Dipyridamole blunted the feedback response, which upregulates HMGCR and HMG-CoA synthase 1 (HMGCS1) following statin treatment. We further show that dipyridamole inhibited the cleavage of the transcription factor required for this feedback regulation, sterol regulatory element-binding transcription factor 2 (SREBF2, SREBP2). Simultaneously targeting the MVA pathway and its restorative feedback loop is preclinically effective against hematologic malignancies. This work provides strong evidence for the immediate evaluation of this novel combination of FDA-approved drugs in clinical trials.

Dipyridamole prevents triple-negative breast-cancer progression

Dipyridamole is a widely prescribed drug in ischemic disorders, and it is here investigated for potential clinical use as a new treatment for breast cancer. Xenograft mice bearing triple-negative breast cancer 4T1-Luc or MDA-MB-231T cells were generated. In these in vivo models, dipyridamole effects were investigated for primary tumor growth, metastasis formation, cell cycle, apoptosis, signaling pathways, immune cell infiltration, and serum inflammatory cytokines levels. Dipyridamole significantly reduced primary tumor growth and metastasis formation by intraperitoneal administration. Treatment with 15 mg/kg/day dipyridamole reduced mean primary tumor size by 67.5 % (p = 0.0433), while treatment with 30 mg/kg/day dipyridamole resulted in an almost a total reduction in primary tumors (p = 0.0182). Experimental metastasis assays show dipyridamole reduces metastasis formation by 47.5 % in the MDA-MB-231T xenograft model (p = 0.0122), and by 50.26 % in the 4T1-Luc xenograft model (p = 0.0292). In vivo dipyridamole decreased activated β-catenin by 38.64 % (p < 0.0001), phospho-ERK1/2 by 25.05 % (p = 0.0129), phospho-p65 by 67.82 % (p < 0.0001) and doubled the expression of IkBα (p = 0.0019), thus revealing significant effects on Wnt, ERK1/2-MAPK and NF-kB pathways in both animal models. Moreover dipyridamole significantly decreased the infiltration of tumor-associated macrophages and myeloid-derived suppressor cells in primary tumors (p < 0.005), and the inflammatory cytokines levels in the sera of the treated mice. We suggest that when used at appropriate doses and with the correct mode of administration, dipyridamole is a promising agent for breast-cancer treatment, thus also implying its potential use in other cancers that show those highly activated pathways.

Establishment and characterization of a new human pancreatic adenocarcinoma cell line with high metastatic potential to the lung

BACKGROUND

Pancreatic cancer is still associated with devastating prognosis. Real progress in treatment options has still not been achieved. Therefore new models are urgently needed to investigate this deadly disease. As a part of this process we have established and characterized a new human pancreatic cancer cell line.

METHODS

The newly established pancreatic cancer cell line PaCa 5061 was characterized for its morphology, growth rate, chromosomal analysis and mutational analysis of the K-ras, EGFR and p53 genes. Gene-amplification and RNA expression profiles were obtained using an Affymetrix microarray, and overexpression was validated by IHC analysis. Tumorigenicity and spontaneous metastasis formation of PaCa 5061 cells were analyzed in pfp-/-/rag2-/- mice. Sensitivity towards chemotherapy was analysed by MTT assay.

RESULTS

PaCa 5061 cells grew as an adhering monolayer with a doubling time ranging from 30 to 48 hours. M-FISH analyses showed a hypertriploid complex karyotype with multiple numerical and unbalanced structural aberrations. Numerous genes were overexpressed, some of which have previously been implicated in pancreatic adenocarcinoma (GATA6, IGFBP3, IGFBP6), while others were detected for the first time (MEMO1, RIOK3). Specifically highly overexpressed genes (fold change > 10) were identified as EGFR, MUC4, CEACAM1, CEACAM5 and CEACAM6. Subcutaneous transplantation of PaCa 5061 into pfp-/-/rag2-/- mice resulted in formation of primary tumors and spontaneous lung metastasis.

CONCLUSION

The established PaCa 5061 cell line and its injection into pfp-/-/rag2-/- mice can be used as a new model for studying various aspects of the biology of human pancreatic cancer and potential treatment approaches for the disease.

Future potential of thymidylate synthase inhibitors in cancer therapy

Thymidylate synthase (TS) catalyses the de novo synthesis of deoxythymidylate and is a key rate-limiting enzyme of DNA synthesis. The primary site of action of the classic antifolate methotrexate is direct inhibition of dihydrofolate reductase, but it also inhibits TS indirectly by diminishing levels of the TS cosubstrate 5,10-methylenetetrahydrofolate. Polyglutamated metabolites of methotrexate also directly bind and inhibit TS. The prototype fluoropyrimidine fluorouracil is metabolised to an irreversible inhibitor of TS and is the standard chemotherapy for gastrointestinal carcinomas. It is also frequently used in combination with other anticancer drugs against breast cancer and head and neck cancers. The clinical efficacy of fluorouracil is routinely increased by concomitant administration of the biomodulating compound leucovorin (folinic acid). Both the success and limitations of these early drugs led to a search for new, more efficacious TS inhibitors active against a broader range of neoplasms. Raltitrexed (ZD1694, Tomudex) is an antifolate TS inhibitor developed over the last decade that is similarly effective, yet better tolerated, than fluorouracil against colorectal cancer. Additional antifolate and fluoropyrimidine-based TS inhibitors continue to be developed. Many of these experimental drugs have been designed to exploit or thwart selective metabolism in neoplasms, including specific mechanisms of resistance. As the curative potential of relatively non-selective antiproliferative drugs like TS inhibitors is limited against most neoplasms, the future role of TS inhibitors will likely continue to be adjunctive in surgically resectable tumours and palliative in combination with other agents for non-resectable disease. Although TS inhibitors will eventually be supplanted by yet to be discovered agents targeting more tumour-specific cellular signalling pathways, they will probably remain important for the above uses for some time. Future advances in the effective use of TS inhibitors may be forthcoming in the form of improved dosing, fewer untoward effects and increased tumour selectivity with novel fluorouracil prodrug formulations. Furthermore, there is emerging evidence that some novel antifolate TS inhibitors are active against a broader range of neoplams, including lung carcinomas and mesothelioma, compared to classical TS inhibitors. Other possible advances to come include effective biomodulation of antifolate TS inhibitors with nucleoside transport inhibitors and individualised patient therapy based on tumour gene expression and resistance patterns (pharmacogenetics).

Acquired resistance of pancreatic cancer cells towards 5-Fluorouracil and gemcitabine is associated with altered expression of apoptosis-regulating genes

OBJECTIVES

Resistance to chemotherapy is a major cause of treatment failure and poor prognosis in pancreatic cancer. Inasmuch as most effects of chemotherapeutic agents are mediated via the activation of apoptosis, the cytotoxic effects of gemcitabine and 5-fluorouracil (FU) in correlation with apoptosis-regulating genes in pancreatic cancer cell lines were analyzed.

METHODS

The cytotoxic effects of 5-FU and gemcitabine in AsPC-1, Capan-1, Mia-PaCa-2 and T3M4 pancreatic cancer cell lines were assessed by growth assays, and mRNA expression levels of pro-apoptotic and anti-apoptotic genes of the Bcl-2 family were analyzed by RNAse protection assays.

RESULTS

Pancreatic cancer cells displayed a wide range of responses towards 5-FU (IC(50) 0.22-4.63 microM) and gemcitabine (11.51-42.2 nM). After repeated treatment with 5-FU, the IC(50) values in Capan-1 and T3M4 cells increased 2.1- and 1.8-fold, respectively, compared to their parental cells. Following recurrent treatment with gemcitabine, the IC(50) values in Capan-1 cells increased significantly (1.5-fold, p < 0.01). RNase protection assay showed a negative correlation between bcl-x(L) and mcl-1 mRNA expression levels and the sensitivity to 5-FU and gemcitabine after 5-FU and gemcitabine treatment. The bax/bcl-2 ratio maintained relatively stable following 5-FU/gemcitabine treatment and reflected the chemotherapeutic sensitivity of these cell lines.

CONCLUSIONS

These findings reveal that pancreatic cancer cell lines are generally resistant to 5-FU and are more sensitive towards gemcitabine. The bax/bcl-2 ratio is predictive of chemotherapy sensitivity, whereas bcl-x(L) and mcl-1 mRNA levels following repeated exposure to 5-FU or gemcitabine are associated with resistance to these drugs. These findings suggest that the activation of anti-apoptotic genes after repeated drug exposure contributes to chemoresistance of pancreatic cancer cells and that blockage of anti-apoptotic genes might enhance chemosensitivity in pancreatic cancer.