Original Contribution
Pharmacologic ascorbate synergizes with gemcitabine in preclinical models of pancreatic cancer

https://doi.org/10.1016/j.freeradbiomed.2011.03.007Get rights and content

Abstract

Conventional treatment approaches have had little impact on the course of pancreatic cancer, which has the highest fatality rate among cancers. Gemcitabine, the primary therapeutic agent for pancreatic carcinoma, produces minimal survival benefit as a single agent. Therefore, numerous efforts have focused on gemcitabine combination treatments. Using a ratio design, this study established that combining pharmacologically achievable concentrations of ascorbate with gemcitabine resulted in a synergistic cytotoxic response in eight pancreatic tumor cell lines. Sensitization was evident regardless of inherent gemcitabine resistance and epithelial–mesenchymal phenotype. Our analysis suggested that the promiscuous oxidative actions of H2O2 derived from pharmacologic ascorbate can culminate in synergism independent of the cancer cell's underlying phenotype and resistance to gemcitabine monotherapy. Gemcitabine–ascorbate combinations administered to mice bearing pancreatic tumor xenografts consistently enhanced inhibition of growth compared to gemcitabine alone, produced 50% growth inhibition in a tumor type not responsive to gemcitabine, and demonstrated a gemcitabine dose-sparing effect. These data support the testing of pharmacologic ascorbate in adjunctive treatments for cancers prone to high failure rates with conventional therapeutic regimens, such as pancreatic cancer.

Section snippets

Cells and chemosensitivity assessment

Human pancreatic carcinoma cell lines BxPC-3, AsPC-1, and SU.86.86 were purchased from the American Type Culture Collection (Manassas, VA, USA). HPAF-II and Hs 766T cells were kindly donated by Dr. Raj Puri, FDA/CBER (Bethesda, MD, USA); MIA PaCa-2 by Dr. Joseph Cullen, University of Iowa (Iowa City, IA, USA); PANC-1 by Dr. Michael Brownstein, J. Craig Venter Institute (Rockville, MD, USA); and the murine line PAN-02 by Dr. Anthony Sandler, Children's Hospital Medical Center (Washington, DC,

In vitro dose–response relationships of gemcitabine and ascorbate either alone or in combination

Dose–response relationships for either gemcitabine or ascorbate cytotoxicity were established in seven human (BxPC-3, AsPC-1, PANC-1, MIA PaCa-2, SU.86.86, HPAF-II, Hs 766T) and one murine (PAN-02) pancreatic cancer cell line. Initial studies established a dose range when cells were exposed to serial dilutions of either gemcitabine or ascorbate and assessed for chemosensitivity after 72 h by MTT assay. Dose–response curves and IC50 values for each cell line are shown in Fig. 1 ordered (1A–1H)

Discussion

Our strategy herein was to apply standard pharmacologic principles to evaluate the chemotherapy pairing of gemcitabine and ascorbate. The findings showed that combining clinically achievable concentrations of pharmacologic ascorbate with gemcitabine increased chemosensitivity across the spectrum of malignant phenotypes represented in our panel of pancreatic cancer cells (Fig. 1, Fig. 2, Fig. 3, Fig. 4, Table 1, Table 2). Using a combination ratio design [24], [25], this study provides evidence

Acknowledgments

This research was supported by an American Cancer Society Institutional Research Pilot Grant (QK84541F) and in part by the Intramural Research Program of the NIDDK, NIH, and The Hilton Family Foundation.

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