RECIPROCAL EXPRESSION OF PLEIOTROPHIN AND MIDKINE IN NORMAL VERSUS MALIGNANT LUNG TISSUES

Abundant evidence suggests that growth factors are important mediators of non-small cell lung cancer (NSCLC) growth. Although multiple growt h factors have been found to be produced by NSCLC tissues, little is k nown about possible differences in growth factor expression between ma lignant and adjacent normal lung tissues. Variation in growth factor e xpression between normal and malignant lung tissues could be potential ly useful diagnostically and therapeutically. In studies reported here , the expression of the angiogenic growth factor pleiotrophin (PTN) an d homolog midkine (MK) was assessed in resected normal and malignant l ung tissues. Primers specific for the two growth factors were used to amplify reverse transcriptase-produced DNA copies of RNA transcripts h arvested from the tissues. This analysis revealed that all normal lung tissues examined (n = 17) expressed PTN but only two expressed MK. Co nversely, all of the resected lung cancers (n = 20) expressed MK but o nly one expressed PTN. These results demonstrated a striking reciproca l expression pattern of MK and PTN in normal versus malignant lung tis sue.