Functional analysis of mild-type and malignant glioma derived CDKN2Aβ alleles: Evidence for an RB-independent growth suppressive pathway

TY - JOUR

T1 - Functional analysis of mild-type and malignant glioma derived CDKN2Aβ alleles

T2 - Evidence for an RB-independent growth suppressive pathway

AU - Arap, Wadih

AU - Knudsen, Erik

AU - Sewell, Duane A.

AU - Sidransky, David

AU - Wang, Jean Y.J.

AU - Huang, H. J.Su

AU - Cavenee, Webster K.

PY - 1997

Y1 - 1997

N2 - The tumor suppressor gene CDKN2A (pl6/MTS1/INK4A), which encodes the cyclin-dependent kinase inhibitor p16(INK4a), is a target of 9p21 deletions during the malignant progression of human gliomas. This gene also encodes a second protein product (human p16β, murine p19(ARF)), which originates from an unrelated exon of CDKN2A (exon 1β) spliced onto exon 2 in an alternate reading frame. Cell cycle arrest by p16β is caused by an as yet unidentified pathway. In order to test the candidacy of p16β as a glioma suppressor, we replaced p16(INK4a), p15(INK4b) and p16β wild-type as well as a series of seven glioma-derived p16β alleles (R87H, A112V, R120H, A121V, G125R, A128A and A128V), into glioma cell lines that had either CDKN2A-/RB+ (U-87MG and U-251MG) or CDKN2A+/RB- (LN-319) endogenous backgrounds and demonstrated that p16β can act as a functional glioma cell growth suppressor. Moreover, p16β, but not p16(INK4a) or p15(INK4b) inhibited the growth of RB-negative LN-319 cells, indicating that p16β likely exerts its effects through an RB-independent pathway. In vitro and in vivo assays of pRB phosphorylation were consistent with this interpretation. Since none of the glioma-derived p16β mutations inactivated their growth suppressive activities, it appears that mutations in CDKN2A exon 2 (which is shared in the coding sequences of p16(INK4a) and p16β) likely exclusively target p16(INK4a).

AB - The tumor suppressor gene CDKN2A (pl6/MTS1/INK4A), which encodes the cyclin-dependent kinase inhibitor p16(INK4a), is a target of 9p21 deletions during the malignant progression of human gliomas. This gene also encodes a second protein product (human p16β, murine p19(ARF)), which originates from an unrelated exon of CDKN2A (exon 1β) spliced onto exon 2 in an alternate reading frame. Cell cycle arrest by p16β is caused by an as yet unidentified pathway. In order to test the candidacy of p16β as a glioma suppressor, we replaced p16(INK4a), p15(INK4b) and p16β wild-type as well as a series of seven glioma-derived p16β alleles (R87H, A112V, R120H, A121V, G125R, A128A and A128V), into glioma cell lines that had either CDKN2A-/RB+ (U-87MG and U-251MG) or CDKN2A+/RB- (LN-319) endogenous backgrounds and demonstrated that p16β can act as a functional glioma cell growth suppressor. Moreover, p16β, but not p16(INK4a) or p15(INK4b) inhibited the growth of RB-negative LN-319 cells, indicating that p16β likely exerts its effects through an RB-independent pathway. In vitro and in vivo assays of pRB phosphorylation were consistent with this interpretation. Since none of the glioma-derived p16β mutations inactivated their growth suppressive activities, it appears that mutations in CDKN2A exon 2 (which is shared in the coding sequences of p16(INK4a) and p16β) likely exclusively target p16(INK4a).

KW - CDKN2A

KW - Malignant glioma

KW - P16(INK4a.)

KW - RB

KW - Tumor suppressor gene

KW - p16β

UR - https://www.scopus.com/pages/publications/0030613650

UR - https://www.scopus.com/pages/publications/0030613650#tab=citedBy

U2 - 10.1038/sj.onc.1201389

DO - 10.1038/sj.onc.1201389

M3 - Article

C2 - 9366518

SN - 0950-9232

VL - 15

SP - 2013

EP - 2020

JO - Oncogene

JF - Oncogene

IS - 17

ER -