Silencing of the polyamine catabolic key enzyme SSAT prevents CDK inhibitor-induced apoptosis in Caco-2 colon cancer cells

Abstract

Roscovitine and purvalanol are purine derivative cyclin-dependent kinase (CDK) inhibitors that induce apoptosis in various types of cancer cells. However, their impact on the apoptotic cell death mechanism requires further elucidation. Natural polyamines putrescine, spermidine and spermine play essential roles in the regulation of cell growth and proliferation. Increased levels of polyamines in cells are considered to be involved in cancer progression. Intracellular polyamine levels are under the control of several catabolic enzymes, such as spermidine/spermine-N-acetyl transferase (SSAT), acetylpolyamine oxidase (APAO) and spermine oxidase (SMO), which could be altered by several therapeutic drugs. However, the possible role of polyamines in drug-induced apoptosis has yet to be clarified. In the present study, our aim was to determine the modulation of the polyamine catabolic pathway related to CDK inhibitor-induced apoptosis in Caco-2 cells. We found that roscovitine and purvalanol (each 20 μM) induced apoptosis by activating caspase-9 and -3, and inhibiting the mitochondrial membrane potential in Caco-2 cells. CDK inhibitors decreased the intracellular putrescine and spermine levels without affecting spermidine levels. Although both roscovitine and purvalanol induced SSAT expression, they did not exert a significant effect on the APAO expression profile. SSAT transient silencing prevented roscovitine-induced apoptosis compared to parental cells. Thus, we concluded that roscovitine and purvalanol significantly induce apoptosis in Caco-2 cells by modulating the polyamine catabolism, and that SSAT could be an important target in evaluating the potential role of polyamines in apoptotic cell death.

CDK inhibitors–induced SSAT expression requires NFκB and PPARγ inMCF-7 breast cancer cells

“…The induction of SSAT is usually accompanied by a decrease in intracellular levels of PA, in particular Spd and Spm. Our results indicated that purvalanol at 20 µM led to a decrease in total PA levels after 24 h. Recent reports suggest that many chemotherapeutic drugs such as polyamine analogues, BENSpm (Huang et al, 2005), roscovitine (Coker et al, 2012), and sulindac (Babbar et al, 2003) lead to the induction of SSAT and a lower intracellular PA pool in MCF-7 and other cancer cells.…”

“…Previous studies reported ROS generation is linked with DNA damage and results in apoptosis (Casero et al, 2003;Arisan et al, 2012). Our previous studies showed that purvalanol and roscovitine induce ROS generation in LNCaP, DU145, PC3 prostate cancer cells, and HCT116 colon cancer cells (Arisan et al, 2012;Coker et al, 2013;. Spm co-treated cells showed a greater increase in DCFDH-DA staining than Spd co-treatment with CDK inhibitor.…”

Epibrassinolide-induced apoptosis regardless of p53 expression via activating polyamine catabolic machinery, a common target for androgen sensitive and insensitive prostate cancer cells

“…In addition we determined that intracellular PA levels were decreased by EBR treatment. There are several reports showing that upregulated SSAT and PAO gene expressions caused the accumulation of high levels of ROS and apoptosis in breast and colon cancer cells lines . At this point, it should be noted that the effect of the serum amine oxidases as a possible sources of H 2 O 2 was excluded by their inhibitoramino guanidine.…”

Enhancing biopharmaceutical attributes of phospholipid complex-loaded nanostructured lipidic carriers of mangiferin: Systematic development, characterization and evaluation

“…For improved understanding, the control cells at all the time points have been assumed as 100% and the cell viability for tested formulations has been calculated accordingly (Coker et al, 2012;Cheah et al, 2014).…”