[Alteration of subcellular distribution of protein kinase C isoforms in swelling-activated multi-drug-resistant gastric cancer cells and its significance].
OBJECTIVE
To study the alteration of expression and subcellular distribution of classical protein kinase (cPKC) isoforms in gastric cancer cells SGC7901 and their multidrug-resistant cell line SGC7901/VCR under condition of swelling activation and to study the significance of such alterations.


METHODS
Immuno-fluorescence technique and Western Blotting were used to determine the expression and subcellular distribution of cPKC isoforms in gastric cancer cells SGC7901 and its multidrug-resistant cell line SGC7901/VCR under normal condition and during continuous hypotonic perfusion. The co-expression of p-glycoprotein (Pgp) and protein kinase C alpha (PKC alpha) was visualized by immunofluorescence double labeling and laser confocus microscopy.


RESULTS
Under the normal condition, the four isoenzymes of cPKC were expressed in both the cell membrane and the nuclei of the gastric cancer cells SGC7901 and their multidrug-resistant cell line SGC7901/VCR; PKC alpha was strongly positively expressed in the multidrug-resistant cells and positively expressed in the drug-sensitive cells; PKC beta I and PKC beta II were positively expressed in both drug-resistant and drug-sensitive cells, and PKC gamma was strongly positively expressed in both cells. In drug-resistant cell line, cell-swelling and translocation of PKC alpha and PKC gamma were observed ten minutes after continuous hypotonic perfusion. Thirty minutes after the perfusion, almost all the PKCalpha was translocated into the cell membrane of SGC7901/VCR, part of the PKC gamma was translocated into the nucleus, and the cell volume increased to two to three times as much as before. Sixty minutes later, the subcellular distribution of PKCalpha and PKC gamma and the cell volume returned to normal. In drug-sensitive cells, 10 approximately 20 minutes after the continuous hypotonic perfusion nearly all the PKCalpha was translocated into the cell membrane, part of PKC gamma was translocated into the cell membrane, and the cell volume increased to two to three times as much as before. Forty minutes later, PKCalpha and PKCgamma had basically returned to normal. The subcellular distribution of PKCbeta I and PKC beta II remained unchanged in both SGC7901 and SGC7901/VCR. Co-expression of Pgy and PKCalpha was observed in both drug-sensitive and drug-resistant cells, especially in the former.


CONCLUSIONS
Only PKCalpha and PKC gamma isoforms play an important role in the regulation of signal transduction of Pgy and cell volume under continuous perfusion and are related to the expression of PKC alpha and Pgy. PKC beta I and PKC beta II may have nothing to do with such processes.
Han
Y
Y
Institute of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China.
Shi
Y
Y
Zhang
H
H
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1 / Q000032:analysis; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D005455:Fluorescent Antibody Technique; D006801:Humans; D007527:Isoenzymes / Q000032:analysis* / Q000502:physiology; D011493:Protein Kinase C / Q000032:analysis* / Q000502:physiology; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000201:enzymology* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured
D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D007527:Isoenzymes; D011493:Protein Kinase C