A study of gene expression in human normal and carcinogenic cell lines using qRT-PCR

Abstract

The susceptibility of human lungs to carcinogens depends on the metabolic balance between activation and detoxification pathways, though for the tumour to develop depcnds on activation of cell immortalisation pathway. The correlation of these
pathways has not been reported.
The present study described the correlation in transcription of genes of two phases of drug metabolism pathways and immortalisation pathway in four lung cell lines namely; a normal lung cell line (CDD32Lu), alveolar adenocarcinoma (A549), pleural adenocarcinoma (1-1460), and a drug resistance large cell carcinoma (COR-L23/5010).
The levels of transcripts of Phase I (CYPL4I, CYPIA2 and CYP2EI), phase II (GSTMJ) and immortalisation (hTERT) genes were investigated. There was evidence suggesting that the transcription of CYPJAI, and CYP/A2 is of cell specific since
CYPIAJ transcribed in the A549 eell line only, while CYPIA2 was transcribed in the H460 cell line. The present study validates the ability of CYPIA2 to be expressed in cell line.
Moreover, the present study showed abundant expression of CYP2E/ and GSTMJ mRNA in normal and lung cancer cell lines suggesting that these genes may play no active role in lung carcinogenesis. In addition, the transcription level of immortalisation gene (hTERT) and telomerase activity was determined and observed in the A549 cell line only.
The novel finding of this research is the cb-transcription of CYPJAJ and JITERT in the A549 cell line. The co-transcription was further analysed by induction of CYPJAJ in all cell lines with the AhR ligands TCDD and 3-MC. The finding reveals the existence of CYPIAI and hTERT co-transcription. Despite the fact that transcription of CYPJAI was observed CYP1A1 activity was not detected even after cell treatment with CYP1A1 inducers. This was possibly due to scarcity of CYP1A! and limited level of haem in the extrahepatic tissue.
This study demonstrated a novel basal and induced co-transcription of CYP1AJ and hTERT. The regulation of co transcription was analysed by silencing CYPIAJ using siRNA technology and observing hTERT knockdown. Silencing of CYP1AI was subsequently downregulate hTERT transcription and reduces cells viability.
The mechanism of co-transcription was investigated to rule out the involvement of suggested AhR signalling pathway. This was carried out by determining the level of mRNA expression of those genes, which their proteins were involved in the AhR
signalling pathway. The results obtained suggest the role of the AhR signalling pathway in the co-transcription of CYPJAJ and hTERT.
The data obtained from gene knockdown experiments revealed silencing of CYPJAJ alters hTERT expression and cell proliferation. The present study suggests that siRNA technology can be used as a reliable tool for the validation of co-transcription. Moreover, the concomitant silencing of CYPJAJ and hTERT and inhibition of cells proliferation not
only validate the co-transcription but also a valuable finding to be considered as a novel therapeutic target, which may contribute to management of lung cancer.
The transcription of CYPIAJ and hTERT has been identified as a cancer risk marker in a diverse range of cancers, the data of the present study suggests the use of CYPJA] 5iRNA as optional gene therapy in cancer management, where CYPJAJ plays a major risk.