IDENTIFICATION OF LDH-RAS P21 PROTEIN COMPLEX AND EXPRESSION OF THESEGENES IN HUMAN OVARIAN-CANCER

Normal ovarian and ovarian cancer tissues from 35 patients were tested for LDH-A-ras protein complex formation, as well as for the expressio n of ras and LDH-A genes. By immunodetection of the immunoprecipitates , LDH-A-ras protein complexes are present in the homogenates of human ovarian tissues (benign and malignant). Two bands of 21 and 36 kDa wer e demonstrated in affinity-purified LDH active fractions by Western bl ot analysis, and these two proteins were proved to he ras p21 and LDH- A by immunodetection, By Northern blot analysis, elevated levels of c- Ki-ras and LDH-A mRNA. transcripts were noted in 49% (17/35) and 40% ( 14/35) of ovarian cancers, respectively. Concurrent high expression of both genes was demonstrated in 11 cases (31%). Tyrosylphosphorylation of LDH-A was demonstrated in normal and malignant ovarian tissues, an d the extent of phosphorylation was correlated with the stage of ovari an cancer. The concurrent elevated expression of ras and LDH-A in the same ovarian tissue may imply that the increased synthesis of LDH-A is due to increased or amplified signaling of the ras-cascade pathway, T he possible biochemical role of the tyrosylphosphorylated LDH-A comple xed with ras p21 in cell transformation and progression of human ovari an cancer is worthy of further investigation. (C) 1997 Academic Press