Abstract 3675: PAN-811 blocks anticancer drug-induced neurotoxicity
Authors: Jiang Zhi-Gang , Fuller Steven , Ghanbari Hossein A. 
Published: May 2015

The side effects of anticancer drugs, such as chemotherapy-induced cognitive impairment or chemobrain, severely limit their dose usage and therapeutic course, and seriously affect quality of life in cancer patients. The mechanisms underlying chemobrain are still unexplained, and there are currently no treatments. The present study aimed to understand neurotoxicological mechanism of anticancer drugs and to develop therapeutic agents for chemobrain.

Antimetabolites methotrexate (MTX) and 5-fluorouracil (5-FU) are widely used chemotherapeutic agents, readily crossing the blood-brain barrier (BBB). An alkylating agent cisplatin (CDDP) has also been reported to induce chemobrain although controversy exists on its capability to pass the BBB. In this study, primary cerebral neurons from embryonic rats were seeded in serum-free culture medium containing 100% antioxidants (AO). Half of the medium was replaced twice with medium without AO at day 7 (50% AO) and 9 (25% AO). By day 13, the neurons were insulted with 100μM MTX, 25μM 5-FU, or 3.5μM CDDP, and treated with 1.25, 2.5, 5 or 10 μM PAN-811·Cl·H2O (PAN-811) for 3 additional days using vehicle as the control. By day 16, media were harvested for LDH assay and cells were photographed at 300x. Five hours following a third medium replacement (12.5% AO), the cells were photographed again and evaluated by MTS analysis.

No neurotoxicity was observed under 50-100% AO conditions for MTX, 5-FU or CDDP treatment. When the AO content was reduced to 25%, MTX and 5-FU all caused 70% and 75% increases in LDH release, and CDDP elicited a 112% increase, without notable morphological changes. When AO content was reduced to 12.5%, morphological cell death (reductions in cell and neurite densities) occurred in each of MTX, 5-FU and CDDP insulted groups. Additionally, 5-FU and CDDP insults resulted in 33% and 66% reductions in MTS readings, respectively. All these indicate a key role of oxidative stress in mediation of the in vitro neurotoxicity.

PAN-811, an anticancer drug candidate targeting ribonucleotide reductase, inhibited MTX-, 5-FU- or CDDP- elicited LDH leakage in the 25% AO condition in a dose-dependently manner; PAN-811 at 3μM suppressed LDH released from MTX- or 5-FU- insulted neurons to control levels, and at 10μM fully blocked CDDP-induced LDH leakage. Furthermore, PAN-811 at 10μM fully inhibited 5-FU-induced MTS reduction, and elevated MTS reading by 48% for CDDP-insulted neurons under 12.5% AO condition. In addition, PAN-811 at 5μM well blocked MTX-, 5-FU- or CDDP- elicited morphological cell death.

Inhibition of neurotoxicity via suppression of oxidative stress by PAN-811 should not interfere with anticancer efficacy of tested drugs since their anticancer activities do not rely on oxidative stress. Besides, PAN-811 has a distinct intracellular target, which may introduce a synergistic effect with a tested drug in suppression of cancer growth, while protecting against chemobrain.

Citation Format: Zhi-Gang Jiang, Steven Fuller, Hossein A. Ghanbari. PAN-811 blocks anticancer drug-induced neurotoxicity. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 3675. doi:10.1158/1538-7445.AM2014-3675