Objective To investigate the correlation between moderate hypoxia and maliglant transformation of colon carcinoma cell line HT-29.  Methods  Hypoxic conditions were produced according to p(O

2

) of tumor in vivo. The heterotypic adhesiveness of HT-29 cells was detected by MTT assay. Their reaction to the hypoxic environment was determined via invasion across a Matrigel-coated Transwell filter. At 0

6

12

24 and 48 h after hypoxia

MMP-2/9 activiti

es were assessed by gelatin zymography

and osteopontin mRNA and protein levels by RT-PCR and Western blot respectively. NF-κB/p65 levels in nucleus was measured by Western blot after extraction of nucleic protein. Results After 24-hour moderate hypoxia

the heterotypic adhesiveness and invasive capacity of HT-29 cells were significantly enchanced. MMP-2

MMP-9 activities under moderate hypoxia for 6 h showed no significant change as compared with that under normoxia

then gradually up-regulated and reached the peak at 24 h. They showed no significant difference between 24 h and 48 h after hypoxia. The expression trend of osteopontin mRNA

protein and NF-κB/p65 protein in nucleus was similar to that of MMP-2

MMP-9 under moderate hypoxia. Conclusion Moderate hypoxia could induce maliglant transformation in HT-29 cells through enhancing heterotypic adhesiveness and invasive capacity and upregulating MMP-2

MMP-9 activities. OPN-NF-κB may be an important regulatory pathway besides HIF-1 under hypoxic condition

which involves maliglant phenotype induced by moderate hypoxia.