Objective: To investigate the expression and pathological mechanism of matrix metalloproteinase (MMP)-9 and hypoxia-inducible factor (HIF)-2α in CD133⁺ lung cancer stem cells.
Methods: Sixty-two cases of lung cancer paraffin embedding tissues were collected from the First Affiliated Hospital of Soochow University between January 2009 and December 2009. Immunohistochemistry (IHC) was used for detection of CD133 expression in lung cancer tissues and the clinical significance was analyzed. Real-time polymerase chain reaction (PCR) was used for the investigation of expression of tumor metastasis associated genes, including MMP-1, MMP-2, MMP-9, HIF-1α, HIF-1β, HIF-2α and tissue inhibitor of metalloproteinase (TIMP)-1, TIMP-2, TIMP-3, TIMP-4. Scrambled siRNA or CD133 siRNA were used to transfect the lung cancer cell line A549, then Control-si-A549 cells and CD133-si-A549 cells were generated respectively. PCR was used to analysis CD133, MMP-9 and HIF-2α genes expression and transwell invasion assay was used to study the invasion ability of A549 cells in two groups.
Results: 51.6% of lung cancer tissues expressed CD133 (P<0.05); the expression level of CD133 was related to tumor metastasis and patients' survival rate (P<0.05). The gene expression of HIF-2α and MMP-9 were increased in CD133⁺ lung cancer cells compared with CD133⁻ cancer cells (1.58 ± 0.39 vs 1.10 ± 0.31, 1.67 ± 0.38 vs 1.05 ± 0.21, all P<0.05), whereas no difference was found in gene expression of MMP-1, MMP-2, HIF-1α, HIF-1β and TIMP-1, TIMP-2, TIMP-3, TIMP-4 (all P>0.05). Compared with the Control-si-A549 cell, the expression of CD133, HIF-2α and MMP-9 (0.24 ± 0.10 vs 0.85 ± 0.23, 0.19 ± 0.09 vs 0.54 ± 0.18, 0.31 ± 0.17 vs 1.12 ± 0.31, all P<0.05) in CD133-si-A549 cell were remarkably decreased. The number of CD133-si-A549 cells migrated to below room was significantly smaller than that of Control-si-A549 cells (207 ± 25 vs 82 ± 10, P<0.05).
Conclusions: The CD133⁺ lung cancer stem cell is correlated to the tumor metastasis and patients' survival. CD133⁺ tumor stem cell can promote the tumor invasion and metastasis via the up-regulation of HIF-2α and MMP-9 expression.