Initial microarray analysis on different fractionated radiation regimens in xenografts with human lung adenocarcinoma

Abstract

Objective To indentify the gene expression on different fractionated radiation regimens with the same total radiation dose in xenografts with human lung adenocareinoma. Methods Forty-eight BALB/c-nu mice, implanted with human lung adenocarcinoma (Anip973), were randomized into 4 groups: normal control greup,60 Gy in 30 fractions conventional radiation group (2 Gy group) ,60 Gy in 10 fractions hypofractionated radiation group (6 Gy group) ,60 Gy in 6 fractions hypofractionaed radiation group (10 Gy group). Gene alterations were investigated with the microchip analytical procedures covering the entire genome. Genes with significantly different expression were further validated by the quantitative real-time polymerase chain reaction (RT-PCR). Results Compared to the 2 Gy group, the expression of the genes related with the cell growth inhibition and apoptesis was increased, while the genes related with the cell proliferation, anti-apoptosis and DNA damage repair were decreased in the 6 Gy and 10 Gy groups. Confirmed by RT-PCR, c-myc gene was distinctly suppressed in the 6 Gy group (2. 9%) comparing with 2 Gy (5.6%) group and 10 Gy (4.8%) group (P=0. 000,P=0. 002) , and was slightly suppressed in the 10 Gy group comparing with 2 Gy group (P = 0. 069). Conclusions In the BALB/c-nu mice implanted with human lung adenocarcinoma, the hypofractionated radiation regimens clearly inhibit the tumor growth more than conventional fractionation group, though with the same total dose. The 6 Gy group seem to be more effective than 10 Gy group in the inhibition of tumor growth. Key words: Cell lines, lung adenocarcinoma; Irradiation, fractionation; Gene expression, microchip analytical procedures