[Establishment and characterization of human lung squamous-carcinoma sublines resistant to...

I have established human lung squamous-carcinoma cell lines resistant to cis-Diamminedichloroplatinum (II) (CDDP), designated PC10-B3 and PC10-E5, from the original cell line PC10, by a stepwise increment of CDDP concentration. An MMT assay revealed that PC10-B3 was 11.4-fold, and PC10-E5 was 19.9-fold more resistant to CDDP than PC10, respectively. PC10-B3 was cross-resistant to CBDCA and 254-S, but not to doxorubicin and etoposide. The level of intracellular platinum accumulation was reduced by about 5 to 8-fold in PC10-B3 when compared with PC10. A two-dimensional gel electrophoresis was used to analyse the relative amount of proteins as between PC10 and its CDDP resistant sublines. The protein spot MW50 kD, pI5.3 was markedly reduced, and the spot MW50kD, pI4.9 was increased in PC10-B3 and PC10-E5 when compared to PC10. The spot MW58kD, pI5.8 newly appeared only in PC10-E5. I collected the most dramatically changed spot, MW50kD, pI5.3 (50kD-5.3), and processed it to determine its peptide sequence. I found that 50kD-5.3 was identical to 50kD, type I keratin (K14). Moreover, a retinoic acid-mediated K14 reduction was concomitant with a 4.0-fold transient increase in CDDP resistance in PC10. Taken together, the reduced intracellular platinum accumulation and the marked decrease of K14 imply that they are important factors in contributing to CDDP resistance in PC10-B3.