SPARC expression induces cell cycle arrest via STAT3 signaling pathway in medulloblastoma cells.
Dynamic cell interaction with ECM components has profound influence in cancer progression. SPARC is a component of the ECM, impairs the proliferation of different cell types and modulates tumor cell aggressive features. We previously reported that SPARC expression significantly impairs medulloblastoma tumor growth in vivo. In this study, we demonstrate that expression of SPARC inhibits medulloblastoma cell proliferation. MTT assay indicated a dose-dependent reduction in tumor cell proliferation in adenoviral mediated expression of SPARC full length cDNA (Ad-DsRed-SP) in D425 and UW228 cells. Flow cytometric analysis showed that Ad-DsRed-SP-infected cells accumulate in the G2/M phase of cell cycle. Further, immunoblot and immunoprecipitation analyses revealed that SPARC induced G2/M cell cycle arrest was mediated through inhibition of the Cyclin-B-regulated signaling pathway involving p21 and Cdc2 expression. Additionally, expression of SPARC decreased STAT3 phosphorylation at Tyr-705; constitutively active STAT3 expression reversed SPARC induced G2/M arrest. Ad-DsRed-SP significantly inhibited the pre-established orthotopic tumor growth and tumor volume in nude-mice. Immunohistochemical analysis of tumor sections from mice treated with Ad-DsRed-SP showed decreased immunoreactivity for pSTAT3 and increased immunoreactivity for p21 compared to tumor section from mice treated with mock and Ad-DsRed. Taken together our studies further reveal that STAT3 plays a key role in SPARC induced G2/M arrest in medulloblastoma cells. These new findings provide a molecular basis for the mechanistic understanding of the effects of SPARC on medulloblastoma tumor cell proliferation.
Department of Cancer Biology and Pharmacology, University of Illinois College of Medicine at Peoria, One Illini Drive, Peoria, IL-61605, United States.
Chandramu
C
Chetty
Ranadheer
R
Dontula
Purnachandra Nagaraju
PN
Ganji
Meena
M
Gujrati
Sajani S
SS
Lakka
D000818:Animals; D059447:Cell Cycle Checkpoints; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002528:Cerebellar Neoplasms / Q000473:pathology*; D006801:Humans; D008527:Medulloblastoma / Q000473:pathology*; D051379:Mice; D015676:Osteonectin / Q000096:biosynthesis* / Q000235:genetics; D050796:STAT3 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D023041:Xenograft Model Antitumor Assays
D015676:Osteonectin; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human