Differential redistribution of transglutaminase isoforms in cisplatin resistant hepatocarcinoma (HEPG2) cells


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Peter Coussons1,Claire Pike2,Dipak Meshram1
1Anglia Ruskin University,2Anglia Ruskin university

Abstract

Background

A major obstacle in the successful treatment of many cancers is a reduction in the effectiveness of chemotherapeutic drugs, caused by the development of drug resistance. The mechanistic basis for chemoresistance is of great current interest and candidate biomarkers for these processes are emerging. The pleiotropic transaminating enzyme Transglutaminase 2 (TG2) is one such protein implicated in cancer drug resistance.

Method

In order to investigate the role(s) of TG2 in drug resistance, we have generated a model of hepatocarcinoma chemotherapy that enables comparison of the effects of cisplatin treatment on the cellular biology of TG2 in cells that had previously been made chemoresistant to cisplatin with those in the parental hepatocarcinoma (HepG2) cell line. Multiple cell biological techniques - including Western blot analysis and confocal microscopy - were then employed to characterise these effects.

Results

A striking difference between parental and chemoresistant (HepG2/cr) cells was observed when Western blot analysis was used to compare the sub-cellular distribution of TG2 isoform expression in purified membrane and cytoplasmic fractions of these cells following treatment with cisplatin. In both types of untreated cells the full-length isoform, TG2 'long form' (TG2-L) was almost completely cytoplasmic in its distribution, and the truncated 'short form' (TG-S) was almost all membrane associated. However, following cisplatin treatment, the TG2-S was lost from the membranous fraction of parental cells and relocated to the cytoplasmic fraction - an effect not seen in HepG2/cr cells.

Conclusion

Taken together with confocal microscopic analysis of uptake of fluorescently labelled cisplatin, these results collectively indicate that TG2 limits the entry of cisplatin into the cytoplasm and the nucleus of chemoresistant HepG2 cells and supports a role for TG2-S as a novel biomarker and possible therapeutic target in cisplatin drug resistance.