RETINOBLASTOMA PROTEIN EXPRESSION IN LUNG-CANCER - AN IMMUNOHISTOCHEMICAL ANALYSIS

Several analyses of the retinoblastoma (RB) gene in lung cancer at the DNA, mRNA and protein levels have recently been reported. In particul ar, small cell lung carcinoma shows a high incidence of RB gene abnorm alities, suggesting that alterations of this gene may participate in t umor development. In the present study, we used an immunohistochemical technique with a monoclonal antibody raised against RB protein (PMG3- 245) to detect its expression in representative paraffin sections of t issues obtained from 108 patients with various types of lung cancer tr eated by surgical resection of the primary tumor. While deletion of RB protein expression was observed in 7 (88%) of 8 small cell lung carci nomas, only 17 (17%) of 100 non-small cell lung carcinomas showed decr eased RB protein levels and 6 (6%) showed no RB protein expression. Th is low incidence of RB protein expression abnormalities in non-small c ell lung carcinomas was significant (p < 0.0001). Thus, in contrast to small cell lung carcinoma, abnormalities in RB protein expression may be minor events in non-small cell lung carcinoma. In addition, no sig nificant correlation was found between abnormalities in RB protein exp ression and clinical factors such as stage, tumor size, and nodal invo lvement in non-small cell lung carcinoma. However, abnormalities in RB protein expression in squamous cell carcinoma were observed only in t he less differentiated types (p = 0.144), and there was a weak but not statistically significant association in non-small cell lung carcinom a between RB protein status and prognosis (p = 0.09). Therefore, in no nsmall cell lung carcinoma, although abnormalities in RB protein appea r not to be closely associated with tumor development, further studies on a larger scale and with a longer-term follow-up are required to de termine the clinicopathological significance of RB gene abnormalities, in particular the relationship between abnormalities of RB protein an d differentiation or prognosis.