Purpose: KAI1 closely correlates with pancreatic cancer metastasis. There might be some factors that protect the cells from a proliferation inhibition by KAI1 in the solid tumors' microenvironment. Hypoxia and ischemia are the main characteristics of the microenvironment within solid tumors. Whether they affect the KAI1 inhibitory effects on cell proliferation is still unclear.
Methods: MiaPaCa-2 human pancreatic cancer cells do not express KAI1 protein. However, after being infected with Ad5-KAI1, they expressed KAI1 protein. We cultured them under hypoxic and serum-free conditions to simulate the solid tumor hypoxic-ischemic microenvironment. The cells were divided into the control, hypoxic, serum-free, and hypoxic with serum-free groups. The proliferation and apoptosis were observed by CCK8 and Annexin V-FITC/PI, respectively. The green fluorescent protein-labeled light chain 3 association with autophagosome membranes was detected by confocal microscopy. The ratio of LC3-II-LC3-I expression level was detected by western blot. Pretreatment of 3-MA was used to inhibit the autophagy. We, then observed whether the hypoxic and serum-free conditions could change the effect of KAI1 on cell survival and whether the pretreatment of 3-MA could inhibit the effect of hypoxic and serum-free conditions on KAI1 function.
Results: Hypoxia and serum-free media effectively reduced the apoptosis and proliferation inhibition caused by KAI1 and was beneficial to the cell survival. 3-MA pretreatment effectively blocked the protective effect of hypoxia and serum-free media on the cells by autophagy block.
Conclusions: Serum-free media and hypoxia protected the MiaPaCa-2 cells from a KAI1-induced apoptosis and proliferation inhibition via autophagy induction.