CDKN1C (p57KIP2) mRNA expression in human retinoblastomas.

PURPOSE

Quantify cyclin dependent kinase inhibitor 1C (CDKN1C or p57KIP2) mRNA levels in human retinoblastoma tumors (RB) and associate with disease phenotype.

METHODS

CDKN1C mRNA expression was quantified in 55 RB, 3 retinoblastoma cell lines, and 12 control retinas by real time PCR. Localization of CDKN1C protein was confirmed by immunohistochemistry. Tumor CDKN1C expression levels were correlated with phenotype.

RESULTS

Fifty-three of 55 tumors showed significantly elevated levels of CDKN1C mRNA relative to age-matched or adult retina controls. No significant difference was seen relative to fetal retinal controls or retinoblastoma cell lines. Immunohistochemistry revealed heterogeneous staining of CDKN1C protein in tumor cells, which was mainly nuclear although some protein appeared to be cytoplasmic. No correlation was observed between the CDKN1C mRNA expression levels and tumor phenotype.

CONCLUSION

High levels of CDKN1C expression are common in RB. It remains to be determined if elevated expression is a protective response to transformation, provides a selective advantage to tumor cells, or simply reflects the presence of dividing cells.