HIGH-FREQUENCY OF ABERRANT P16(INK4A) EXPRESSION IN HUMAN BREAST-CANCER

The product of the CDKN2/MTS1 gene, p16(INK4A) (p16), inhibits phospho rylation of the retinoblastoma protein, pRB, and thus acts as a negati ve cell cycle regulator, It is inactivated ill a wide range of human m alignancies., including breast cancer Using an immunohistochemical app roach, zee studied the expression of both p16 and pRB in 104 archival breast tumors, including 63 ductal, 33 lobular, and 8 mixed carcinomas . All specimens except one were evaluable for pRB expression, but only 87 were interpretable for p16 expression, reflecting the lower abunda nce and greater lability, of this protein. Only six tumors showed abno rmal RE expression, However, 43 carcinomas (49%) were completely (35) or focally (8) negative for p16. Abnormal p16 expression did not signi ficantly correlate with several histopathological parameters These fin dings provide evidence that aberrant p16(INK4A) expression is one of t he most common abnormalities in human breast cancer.