The role of the polyamine catabolic enzymes SSAT and SMO in the synergistic effects of standard chemotherapeutic agents with a polyamine analogue in human breast cancer cell lines

Abstract

Polyamine analogues have demonstrated significant activity against human breast cancer cell lines as single agents as well as in combination with other cytotoxic drugs. This study evaluates the ability of a polyamine analogue N 1 , N 11 -bis(ethyl)norspermine (BENSpm) to synergize with six standard chemotherapeutic agents, 5-fluorouracil (FU), fluorodeoxyuridine, cis-diaminechloroplatinum(II) (DDP), paclitaxel, docetaxel, and vinorelbine, in four human breast cancer cell lines and one immortalized, non-tumorigenic mammary epithelial cell line. BENSpm exhibited synergistic inhibitory effect on cell proliferation in combination with 5-FU or paclitaxel in human breast cancer cell lines (MDA-MB-231 and MCF-7) and either antagonistic or less effective in the non-tumorigenic MCF-10A cell line. Synergism was highest with 120 hour concomitant treatment or pre-treatment with BENSpm for 24 hours followed by concomitant treatment for 96 additional hours. Since the cytotoxic effects of many polyamine analogues and cytotoxic agents are believed to act, in part, through induction of the polyamine catabolic enzymes SSAT and SMO, the role of these enzymes on synergistic response was evaluated in MDA-MB-231-and MCF-7-treated with BENSpm and 5-FU or paclitaxel. Combination treatments of BENSpm with 5-FU or paclitaxel resulted in induction of SSAT mRNA and activity in both cell lines compared to either drug alone, while SMO mRNA and activity were increased only in MDA-MB-231 cells. Induction was greater with BENSpm/ paclitaxel combination than BENSpm/5-FU. Further, RNAi studies demonstrated that both SSAT and SMO play a significant role in the response of MDA-MB-231 cells to treatment with BENSpm and 5-FU or paclitaxel. In MCF-7 cells, only SSAT appears to be involved in the response to these treatments. In an effort to translate combination studies from in vitro to in vivo, and to form a basis for clinical setting, the in vivo therapeutic efficacy of BENSpm alone and in combination with paclitaxel on tumor regression was evaluated in xenograft mice models generated with MDA-MB-231 cells. Intraperitoneal exposure to BENSpm or taxol singly and in combination for 4 weeks resulted in significant inhibition in tumor growth These findings help elucidate the mechanisms

Spermine oxidase (SMO) activity in breast tumor tissues and biochemical analysis of the anticancer spermine analogues BENSpm and CPENSpm

“…BENSpm and CPENSpm have been successfully employed as antiproliferate compounds on some human BC cell lines [11,15,17,18] but in Phases I and II of clinical trials gave poor positive outcomes [14,18,20-22]. The H 2 O 2 produced through BENSpm-induced PA catabolism was found to be derived exclusively from SMO and not through APAO activity.…”

Targeting polyamine metabolism for cancer therapy and prevention

“…In addition to meeting the above criteria for intended effects on polyamine metabolism, it was also discovered that one of the major mechanisms of action of the analogs was to significantly increase polyamine catabolism and its concurrent production of reactive oxygen species (ROS) in a tumor-type-specific manner [74–77]. Although this increase in ROS production was originally thought to be a consequence of increased SSAT activity followed by oxidation of the acetylated polyamines by PAOX, more recent studies have demonstrated that the polyamine analogs also efficiently induce SMOX, which appears to be the primary source of ROS, rather than PAOX [78–80]. Regardless, these findings of selective toxicity bolstered the rational for this class of compounds entering the clinical trial.…”

Polyamine catabolism in carcinogenesis: potential targets for chemotherapy and chemoprevention

“…Indeed, several polyamine analogues have been described to induce the expression of both SSAT and SMO to trigger cancer cell death or decrease cell proliferation, demonstrating a potential for chemotherapy that has not yet been fully exploited. For example, the polyamine analogue N 1 , N 11 -bis(ethyl)norspermine (BENSpm) is able to induce the expression of both SSAT and SMO and has been used in combination with standard chemotherapeutic agents in breast cancer cell lines to cause increased antiproliferative effects (Pledgie-Tracy et al 2010). …”