Ganglioside GM3 modulates tumor suppressor PTEN-mediated cell cycle progression--transcriptional induction of p21(WAF1) and p27(kip1) by inhibition of PI-3K/AKT pathway.
The simple ganglioside GM3 has been shown to have anti-proliferative effects in several in vitro and in vivo cancer models. Although the exogenous ganglioside GM3 has an inhibitory effect on cancer cell proliferation, the exact mechanism by which it prevents cell proliferation remains unclear. Previous studies showed that MDM2 is an oncoprotein that controls tumorigenesis through both p53-dependent and p53-independent mechanisms, and tumor suppressor phosphatase and tensin homolog deleted on chromosome 10 (PTEN), a dual-specificity phosphatase that antagonizes phosphatidylinositol 3-kinase (PI-3K)/AKT signaling, is capable of blocking MDM2 nuclear translocation and destabilizing the MDM2 protein. Results from our current study show that GM3 treatment dramatically increases cyclin-dependent kinase (CDK) inhibitor (CKI) p21(WAF1) expression through the accumulation of p53 protein by the PTEN-mediated inhibition of the PI-3K/AKT/MDM2 survival signaling in HCT116 colon cancer cells. Moreover, the data herein clearly show that ganglioside GM3 induces p53-dependent transcriptional activity of p21(WAF1), as evidenced by the p21(WAF1) promoter-driven luciferase reporter plasmid (full-length p21(WAF1) promoter and a construct lacking the p53-binding sites). Additionally, ganglioside GM3 enhances expression of CKI p27(kip1) through the PTEN-mediated inhibition of the PI-3K/AKT signaling. Furthermore, the down-regulation of the cyclin E and CDK2 was clearly observed in GM3-treated HCT116 cells, but the down-regulation of cyclin D1 and CDK4 was not. On the contrary, suppression of PTEN levels by RNA interference restores the enhanced expression of p53-dependent p21(WAF1) and p53-independent p27(kip1) through inactivating the effect of PTEN on PI-3K/AKT signaling modulated by ganglioside GM3. These results suggest that ganglioside GM3-stimulated PTEN expression modulates cell cycle regulatory proteins, thus inhibiting cell growth. We conclude that ganglioside GM3 represents a modulator of cancer cell proliferation and may have potential for use in colorectal cancer therapy.
Department of Biological Science, Sungkyunkwan University, Suwon City, Kyunggi-Do, South Korea.
Hee-Jung
HJ
Choi
Tae-Wook
TW
Chung
Sung-Koo
SK
Kang
Young-Choon
YC
Lee
Jeong-Heon
JH
Ko
Jong-Guk
JG
Kim
Cheorl-Ho
CH
Kim
D000970:Antineoplastic Agents / Q000032:analysis / Q000494:pharmacology* / Q000627:therapeutic use; D002453:Cell Cycle / Q000187:drug effects; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000737:chemistry; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics*; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015536:Down-Regulation; D005679:G(M3) Ganglioside / Q000032:analysis / Q000494:pharmacology* / Q000627:therapeutic use; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D051059:PTEN Phosphohydrolase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000494:pharmacology; D014158:Transcription, Genetic; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D000970:Antineoplastic Agents; C493956:CDKN1A protein, human; C436291:CDKN1B protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D005679:G(M3) Ganglioside; D047908:Intracellular Signaling Peptides and Proteins; D000081082:Phosphoinositide-3 Kinase Inhibitors; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051057:Proto-Oncogene Proteins c-akt; D051059:PTEN Phosphohydrolase