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Tubulin polymerization promoting protein 3 (TPPP3), a member of the TPPP family, can induce tubulin polymerization and microtubule bundling. Previously, it has been shown that TPPP3 plays an important role in cell proliferation. Depletion of TPPP3 by microRNA-based RNA interference (RNAi) inhibits cell growth, arrests cell cycles, and causes mitotic abnormalities in HeLa cells. In the present study, we knocked down TPPP3 in Lewis lung carcinoma (LLC) cells with the same RNAi construct, and observed a retarded tumor cell growth in vitro. Furthermore, C57BL/6 mice that received subcutaneously injected LLC cells in which TPPP3 was knocked down showed a pronounced reduction in tumor progression. The migration/invasion activity of TPPP3-knockdown LLC cells was significantly suppressed in a transwell chamber migration assay. When these cells were injected into the tail veins of C57BL/6 mice, they exhibited milder lung metastasis compared with control tumor cells. Taken together, these findings suggested that the TPPP3 gene played an important role in tumorigenesis and metastasis, and it could potentially become a novel target for cancer therapy.

Microtubules (MTs) play an important role in cell division, and their functions are regulated by a set of microtubule-associated proteins (MAPs). Tubulin polymerization promoting protein family member 3 (TPPP3), also known as p20, is a new member of the tubulin polymerization promoting protein (TPPP) family. Previous studies have demonstrated that TPPP3 specifically binds to MTs and positively regulates MTs assembly, which leads to significant ultrastructural alterations of the MTs network. However, the physiological function of TPPP3 is still largely unknown. In the present study, we showed that knockdown of endogenous TPPP3 by RNA interference (RNAi) suppressed cell proliferation and induced cell cycle arrest in HeLa cells. Furthermore, we showed that the depletion of TPPP3 caused mitotic abnormalities, such as the formation of multipolar spindles and chromosome segregation errors, which lead to apoptosis in HeLa cells. Our study suggested that TPPP3 played a crucial role in cell mitosis by regulating centrosomes amplification and/or spindles translocation processes.