Cancer Resources > Cancer News > 2003 > November

PABA sensitizes tumor cells to chemotherapy and radiation

Last Updated: 2003-11-19 17:00:22 -0400 (Reuters Health)

NEW YORK (Reuters Health) - Results of culture and animal studies suggest that p-aminobenzoic acid (PABA) may boost the anti-cancer effects of radiation and chemotherapy drugs.

Dr. Peter Brooks described the studies in Boston today during the International Conference on Molecular Targets and Cancer Therapeutics, sponsored by the American Association for Cancer Research, the National Cancer Institute, and the European Organization for Research and Treatment of Cancer.

Recently, it has been shown that PABA, an ingredient in some sunscreens and a supplement found in certain cell culture growth media, is capable of inhibiting the development of melanoma in vitro.

This led Dr. Brooks and colleagues at New York University School of Medicine to culture highly melanotic B16F10 melanoma cells as well as lung and breast carcinoma cells in the presence or absence of PABA.

"PABA by itself had little effect on proliferation, however if these cells were treated with PABA and then treated with ionizing radiation and/or chemotherapy we got substantial inhibition of proliferation," Dr. Brooks said.

They obtained similar results in melanoma-bearing mice. A significant decrease in tumor progression was noted among tumors treated with PABA plus Taxol and/or ionizing radiation compared to tumors left untreated or treated with Taxol alone.

Although it's not clear exactly how PABA acts, results of differential cDNA array analysis suggest that PABA up-regulates cell cycle control genes and down-regulates DNA repair enzymes.

"What PABA appears to be doing is setting the cell up to die," Dr. Brooks said. "It's reducing the cell's ability to repair itself after the damage is done and at the same time regulating its proliferative capacity by disrupting normal cell cycle checkpoints," he continued.

These results point to PABA as a means of optimizing existing cancer therapies. A clinical trial is just getting underway at New York University looking at combinations of PABA and Taxol in melanoma patients.

"Because the toxicities and clinical parameters of PABA are already known in humans, the translation of this into the clinic should be relatively rapid," Dr. Brooks predicted.

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