CYCLIN D1 OVEREXPRESSION IN NONSMALL CELL LUNG-CARCINOMA - CORRELATION WITH KI67 LABELING INDEX AND POOR CYTOPLASMIC DIFFERENTIATION

Cyclin D1 is part of the molecular system regulating the cell cycle G1 to S transition point. Its overexpression, a common finding in carcin omas of the breast, oesophagus, and head and neck, has also been demon strated in a high percentage of non-small cell lung carcinomas (NSCLCs ). The role of cyclin D1 in NSCLC has been studied by correlating its immunoreactivity with the Ki67 labelling index in paraffin-embedded, a utoclaved surgical samples of 56 NSCLC cases. In addition, pow cytomet ric determination of ploidy and cell cycle status was carried out on 1 72 fresh tumour samples from the same cases. Twenty-four (42 . 8 per c ent) NSCLCs showed positive cyclin D1 immunostaining, a finding which showed no relationship to ploidy pattern, cell cycle phase, histologic al subtype, or lymph node metastasis, but was significantly associated with the Ki67 labelling index (P=0 . 03) and with poor cytoplasmic di fferentiation (P=0 . 01). Cyclin D1-positive nuclei were abundant in p oorly differentiated zones and absent in the best differentiated areas , particularly in heavily keratinized fields. These data indicate that in NSCLC, cyclin D1 overexpression is not only associated with a high cell proliferation rate, but also seems to play a role in the process of tumour differentiation.