CAMSAP3 negatively regulates lung cancer cell invasion and angiogenesis through nucleolin/HIF-1α mRNA complex stabilization.

Aims: Cancer metastasis is a major cause of lung cancer-related mortality, so identification of related molecular mechanisms is of interest. Calmodulin-regulated spectrin-associated protein 3 (CAMSAP3) has been implicated in lung cancer malignancies; however, its role in metastatic processes, including invasion and angiogenesis, is largely unknown.

Main Method: The clinical relevance of CAMSAP3 expression in lung cancer was evaluated. The relevance of CAMSAP3 expression to in vitro cell invasion and angiogenesis was assessed in human lung cancer cells and endothelial cells, respectively. The molecular mechanism was identified by qRT-PCR, immunoprecipitation, mass spectrometry, and RNA immunoprecipitation. The in vivo metastatic and angiogenic activities of lung cancer cells were assessed.

Key Findings: Low CAMSAP3 expression was found in malignant lung tissues and strongly correlated with a poor prognosis in lung adenocarcinoma (LUAD). CAMSAP3-knockout NSCLC exhibited high invasive ability, and CAMSAP3 knockout induced HUVEC proliferation and tube formation; these effects were significantly attenuated by reintroduction of exogenous wild-type CAMSAP3. Mechanistically, in the absence of CAMSAP3, the expression of hypoxia-inducible factor-1α (HIF-1α) was upregulated, which increased the levels of downstream HIF-1α targets such as vascular endothelial growth factor A (VEGFA) and matrix metalloproteinases (MMPs) 2 and 9. Proteomic analysis revealed that nucleolin (NCL) bound to CAMSAP3 to regulate HIF-1α mRNA stabilization. In addition, CAMSAP3-knockout lung cancer cells displayed highly aggressive behavior in metastasis and angiogenesis in vivo.

Significance: This study reveals that CAMSAP3 plays a negative regulatory role in lung cancer cell metastatic behavior both in vitro and in vivo through NCL/HIF-1α mRNA complex stabilization.