In pancreatic cancer whose microenvironment is extremely hypoxic condition, the analysis of signal transduction under hypoxia is thought to be significantly important. By investigating microarray analysis of pancreatic cancer cultured between under normoxia and under hypoxia, we found that the expression of leukocyte common antigen related (LAR)- interacting protein (liprin)-α4 was extremely increased under hypoxia compared to under normoxia. In the present study, the biological significance of liprin-α4 in pancreatic cancer was investigated and whether liprin-α4 could be a therapeutic target for this refractory cancer was estimated.
Three pancreatic ductal adenocarcinoma cell (PDAC) lines (ASPC-1, SUIT-2, and PANC-1) were cultured under normoxia (20%O2) and under hypoxia (1%O2), and were used as target cells. Inhibition of liprin-α4 was performed using liprin-α4 siRNA. Expression of liprin-α4 was analyzed by real time RT-PCR, western blot and immunofluorescent staining. Proliferation was estimated by cell count and MTT assay. Invasion was estimated by matrigel invasion assay. Mice xenograft experiments were performed using BALB/c nude female mice. Surgically resected human pancreatic cancer specimens were used for immune staining.
1) Expression of liprin-α4 was increased in PDAC under hypoxia compared to normoxia. 2) Liprin-α4 suppression decreased invasion through inhibition of endothelial mesenchymal transition in PDAC under hypoxia. 3) Liprin-α4 inhibition decreased proliferation of PDAC under hypoxia In vitro. 4) Tumor volume in mice injected with liprin-α4-inhibited PDAC was significantly lower than that in control mice. 5) Signaling from liprin-α4 was through PI3K and MAPK signaling pathways. 6) Relation between hypoxia inducible factor-1α (HIF-1α) expression and liprin-α4 expression was observed by immunofluorescent staining using surgically resected pancreatic cancer specimen.
These results suggest that liprin-α4 which is more expressed under hypoxia, plays pivotal role for inducing malignant phenotype such as proliferation and invasion in pancreatic cancer, and that liprin-α4 could be an effective therapeutic target for pancreatic cancer.
Clinical trial identification
Legal entity responsible for the study
Cancer Therapy and Research, Kyushu University Hospital,
All authors have declared no conflicts of interest.