A Comparative Study Of Residual Cell Growth,Apoptosis And Stem Cell Changes After Radiation In Two Lung Adenocarcinoma Xenografts

Objective:To establish a post-irradiation residual tumor subcutaneous xenograft model in normal lung adenocarcinoma A549 cells or Xuanwei female lung adenocarcinoma(XWLC-05 cells)in nude mice.To investigate the changes of cells growth,apoptosis,cell cycles,and cancer stem cells in two types of lung adenocarcinoma after radiation,and the differences in the biological behavior of residual lung cells after radiation.Methods:A549 cells and XWLC-05 cells were implanted in the left atlas of BALB/C-nu nude mice aged at 3-4 weeks to construct a transplanted tumor model.After the tumor volume reached 1 cm3,a 20Gy X-ray radiation was performed on the tumor tissue.When the volume of residual tumor tissue after radiation was reduced to a certain size,the residual tumor tissue blocks were re-planted in the left iliac crest of BALB/C-nu nude mice aged at 3-4 weeks to construct transplantable residual tumors model.The tumor volume changes were monitored regularly and the growth curve of the transplanted tumors was regularly monitored;nude mice were sacrificed 0 days,7 days,14 days,21 days,and 28 days after the residual tumor tissue had grown to 0.5 cm3,and the morphological changes of transplanted tumor tissues were taken and observed by HE staining.Cell apotosis;cell cycle distribution,and the proportion of CD44 and CD133-tagged cancer stem cells were measured by flow cytometry.Compare changes and differences between groups.Results:1.After being stained by HE tumor tissue,we observed tissue morphology under the microscope was full with the characteristics of the tumor cells.After irradiation,the interstitial cells in the remnant tumors were significantly higher than those in pre-irradiation tumor tissues.2.The growth rate of both lung adenocarcinoma xenografts and residual tumors increased with time.The implanted tumor volume first increased and then decreased after irradiation.After irradiation,the growth rate of XWLC-05 nude mice was lower than that of non-irradiated tumors.Slowly,after irradiation,the growth speed of residual tumors of A549 nude mice was higher than that of non-irradiated tumors;XWLC-05 before and after irradiation grown faster than A549 tumors and residual tumors.3.There was no significant difference in the XWLC-05 xenograft tumors and residual tumors in S phase and G2/M phase.After radiation,the G2/M phase reached the highest after 21 days of tumor formation and then began to decrease.There was no significant difference in G1/G0 phase,S phase,and G2/M phase in transplanted tumors and residual tumors of A549 nude mice.The proportion of G2/M phase cells in the nude mice reached the highest level 14 days after tumor formation and decreased afterwards.There was no significant difference in the G2/M phase between transplanted tumors of A549 nude mice and XWLC-05 nude mice in the same group.4.After irradiation,XWLC-05 xenograft in nude mice and xenograft in A549 nude mice reached the peak value and then decreased when the tumors were tumorigenic for 0 days and the tumors in the remaining tumors were replanted.Both types of lung in the same group were no statistical difference in the rate of cancer apoptosis.5.The percentage of CD44+CD133+ stem cells in XWLC-05 transplanted tumors increased after irradiation,increased to the peak when the residual tumors were sacrificed,and then gradually decreased;the ratio of stem cells of transplanted tumors in A549 nude mice showed a decreasing-rising trend after radiation,to the residual Tumors were tumorigenic and peaked at 21 days and then decreased;there was a statistically significant difference in the proportion of CD44+CD133H+ stem cells in XWLC-05 compared to the A549 nude mice transplanted tumors group(2.70±2.66 vs 23.02±11.29,p<0.01).Conclusions:1.XWLC-05 has faster growth speed and higher radiosensitivity than A549 xenografts.Post-radiation XWLC-05 tumours grown slower than non-radiation tumours while A549 post-radiation tumours are quicker than before.2.The proportion of G2/M phase cells in both kinds of lung adenocarcinoma xenografts are decreased after radiation.3.post-irradiation apoptosis of two types lung adenocarcinoma xenografts were increase.4.The proportion of CD44+CD133+ stem cells in XWLC-05 transplanted tumors increased significantly after radiation,and A549 wasn't.