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Tumour Biol. 2016 Feb;37(2):1727-38. doi: 10.1007/s13277-015-3959-0. Epub 2015 Aug 28.

Aspirin and salicylic acid decrease c-Myc expression in cancer cells: a potential role in chemoprevention.

Author information

1
Department of Pharmaceutical Sciences, South Dakota State University College of Pharmacy, Avera Health and Sciences Center, Brookings, SD, 57007, USA.
2
Department of Pharmaceutical Sciences, South Dakota State University College of Pharmacy, Avera Health and Sciences Center, Brookings, SD, 57007, USA. Jayarama.gunaje@sdstate.edu.

Abstract

Epidemiological studies have demonstrated a significant correlation between regular aspirin use and reduced colon cancer incidence and mortality; however, the pathways by which it exerts its anti-cancer effects are still not fully explored. We hypothesized that aspirin's anti-cancer effect may occur through downregulation of c-Myc gene expression. Here, we demonstrate that aspirin and its primary metabolite, salicylic acid, decrease the c-Myc protein levels in human HCT-116 colon and in few other cancer cell lines. In total cell lysates, both drugs decreased the levels of c-Myc in a concentration-dependent fashion. Greater inhibition was observed in the nucleus than the cytoplasm, and immunofluorescence studies confirmed these observations. Pretreatment of cells with lactacystin, a proteasome inhibitor, partially prevented the downregulatory effect of both aspirin and salicylic acid, suggesting that 26S proteasomal pathway is involved. Both drugs failed to decrease exogenously expressed DDK-tagged c-Myc protein levels; however, under the same conditions, the endogenous c-Myc protein levels were downregulated. Northern blot analysis showed that both drugs caused a decrease in c-Myc mRNA levels in a concentration-dependent fashion. High-performance liquid chromatography (HPLC) analysis showed that aspirin taken up by cells was rapidly metabolized to salicylic acid, suggesting that aspirin's inhibitory effect on c-Myc may occur through formation of salicylic acid. Our result suggests that salicylic acid regulates c-Myc level at both transcriptional and post-transcription levels. Inhibition of c-Myc may represent an important pathway by which aspirin exerts its anti-cancer effect and decrease the occurrence of cancer in epithelial tissues.

KEYWORDS:

Aspirin; Colon cancer; Proteasome; Salicylic acid; c-Myc

PMID:
26314861
DOI:
10.1007/s13277-015-3959-0
[Indexed for MEDLINE]

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