Reciprocallity between status of pRb and that of p16INK4a commonly found in human permanent cell lines (including cervical cell line cultures) [17,20,21] as well as in primary tumor cells [9,22,23] served for a logical prerequisite of utilizing p16INK4a protein as a marker of premalignant and malignant cervical epithelium cells. This evidence concerns the gene CDKN2A and neoplasm.