EXPRESSION OF CELL-CYCLE REGULATING FACTOR MESSENGER-RNA IN SMALL-CELL LUNG-CANCER XENOGRAFTS

We have investigated the expression of cyclins, cyclin dependent kinas es (CDK), and CDK inhibitors (CKI) at the mRNA level in a panel of sma ll-cell lung cancer (SCLC) cell lines in vitro and in vivo as xenograf ts in nude mice. The results showed that the cell lines expressed vary ing amounts of most cyclin and CDK's but only a few of the cell lines expressed cyclin D-1 and/or D-2 and some lacked expression of CDK6. Mo st cell lines expressed mRNA for the CKI's but two cell lines lacked e xpression of p15(INK4B) and p16(INK4A). The mRNA expression differed f or a few of the cell, lines regarding cyclin D-2 and CDK6 when in vitr o and in vivo data were compared. Two of the cell lines that express t he retinoblastoma (Rb) protein had no sign of a deregulated Rb pathway but further studies at the protein level are necessary to demonstrate whether these two cell lines should have a normal Rb pathway or wheth er they will join the majority of cell lines with deregulated Rb pathw ay.