Panoply™ Human PLK1 Knockdown Stable Cell Line

PLK1 is a typical PLK protein and a major driver of cancer cell growth and proliferation. It is often used as a tumor marker because high levels of PLK1 expression are associated with poor cancer prognosis. MYC overexpression is a hallmark of many human cancers. MYC regulates the transcription of thousands of genes that are required to coordinate a range of cellular processes, including those critical for growth, proliferation, differentiation, self-renewal, and apoptosis. Here, the study shows that PLK1 or MYC promotes osteosarcoma cell proliferation through the autophagy pathway. PLK1 contributes to the stability of MYC protein. PLK1 inhibition enhances the degradation of MYC in osteosarcoma cells. PLK1 inhibition leads to a significant decrease in MYC protein abundance. PLK1 inhibitors cause dysregulation of the expression of representative MYC target genes. BI2536 treatment significantly delayed the growth of xenograft tumors in mice subcutaneously injected with U-2 OS cells, resulting in lower average tumor weight compared to the control group. These data confirm that PLK1 is a potential therapeutic target for osteosarcoma caused by MYC amplification.

To investigate the role of PLK1 in osteosarcoma cells, Western blot and BrdU assays were performed after stable knockdown of PLK1 or treatment with a PLK1-specific inhibitor. As shown in Figure 1B, in PLK1-knockdown U-2 OS and Saos-2 cells, the levels of LC3-II/LC3-I and ATG5 were significantly reduced, indicating that autophagosome formation was inhibited; significant accumulation of SQSTM1 was observed after PLK1 knockdown, suggesting a defect in the autophagic-lysosomal pathway. To accurately assess autophagic activity under PLK1 deficiency, the researchers measured LC3-II levels after Baf A1 treatment. The results showed that LC3-II levels were significantly increased after Baf A1 treatment in PLK1-knockdown cells (Figure 1C). Furthermore, PLK1 deficiency significantly impaired autophagy (Figure 1D). Given that autophagy is an important mechanism for cancer cell proliferation under basal conditions, the researchers performed BrdU assays after stable knockdown of PLK1 or treatment with a PLK1-specific inhibitor. The data showed that BrdU uptake was significantly reduced in PLK1-knockdown cells compared to the control group (Figure 1E). Consistent with these results, the PLK1-specific inhibitor BI2536 inhibited cell proliferation (Figure 1F). Next, the researchers conducted cell proliferation experiments under conditions of stable PLK1 downregulation and autophagy deficiency. The results showed that cell proliferation was further inhibited under autophagy-deficient conditions (Figure 1G). These data indicate that PLK1 promotes the proliferation of osteosarcoma cells through the autophagy pathway.

Figure 1. PLK1 promotes the proliferation of osteosarcoma cells. (Mo H, et al., 2019)