Mis12 controls cyclin B1 stabilization via Cdc14B-mediated APC/CCdh1 regulation during meiotic G2/M transition in mouse oocytes.

Mammalian oocytes are arrested at G2/prophase of the first meiosis. After a hormone surge, oocytes resume meiosis, undergoing germinal vesicle breakdown (GVBD). This process is regulated by Cdk1/cyclin B1. Here, we report that Mis12 is required for G2/M transition by regulating cyclin B1 accumulation via Cdc14B-mediated APC/CCdh1 regulation, but is not essential for spindle and chromosome dynamics during meiotic maturation. Depletion of Mis12 severely compromised GVBD by impairing cyclin B1 accumulation. Importantly, impaired GVBD after Mis12 depletion was rescued not only by overexpressing cyclin B1 but also by depleting Cdc14B or Cdh1. Notably, oocytes rescued by cyclin B1 overexpression exhibited normal spindle and chromosome organization with intact kinetochore-microtubule attachments. In addition, after being rescued by cyclin B1 overexpression, Mis12-depleted oocytes normally extruded polar bodies. Moreover, Mis12-depleted oocytes formed pronuclear structures after fertilization but failed to develop beyond zygotes. Interestingly, Mis12 was localized in the cytoplasm and spindle poles in oocytes, in contrast to kinetochore localization in somatic cells. Therefore, our results demonstrate that Mis12 is required for meiotic G2/M transition but is dispensable for meiotic progression through meiosis I and II.

Centrosome de-clustering of cancer cells induces cGAS-STING-mediated innate immunity of tumor-associated tumor cells in response to irradiation.

Although radiotherapy (RT) increases the extra centrosomes of cancer cells compared to normal cells, centrosome clustering of cancer cells with amplified centrosomes ensures bipolar mitosis for cell proliferation in response to RT. Recent evidence suggests that centrosome clustering is a tumor-selective target for improving RT in breast cancer cells. However, whether centrosome de-clustering is involved in the activation of innate immunity in response to RT remains unknown. In this study, we showed that centrosome de-clustering of irradiated cancer cells modulates cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-mediated innate immunity in monocytes and macrophages after co-culture. Centrosome de-clustering intensifies mitotic abnormalities and cytosolic dsDNA in breast cancer cells in response to irradiation. Unexpectedly, centrosome de-clustering did not modulate the cGAS-STING signaling pathway in irradiated breast cancer cells. Importantly, centrosome de-clustering activated the cGAS-STING signaling pathway in human monocytes and mouse macrophages after co-culture with irradiated breast cancer cells. Thus, our data provide the first evidence that centrosome de-clustering of irradiated breast cancer cells induces innate immunity in tumor-associated immune cells.

CIP2A acts as a scaffold for CEP192-mediated microtubule organizing center assembly by recruiting Plk1 and aurora A during meiotic maturation.

In somatic cells spindle microtubules are nucleated from centrosomes that act as major microtubule organizing centers (MTOCs), whereas oocytes form meiotic spindles by assembling multiple acentriolar MTOCs without canonical centrosomes. Aurora A and Plk1 are required for these events, but the underlying mechanisms remain largely unknown. Here we show that CIP2A regulates MTOC organization by recruiting aurora A and Plk1 at spindle poles during meiotic maturation. CIP2A colocalized with pericentrin at spindle poles with a few distinct cytoplasmic foci. Although CIP2A has been identified as an endogenous inhibitor of protein phosphatase 2A (PP2A), overexpression of CIP2A had no effect on meiotic maturation. Depletion of CIP2A perturbed normal spindle organization and chromosome alignment by impairing MTOC organization. Importantly, CIP2A was reciprocally associated with CEP192, promoting recruitment of aurora A and Plk1 at MTOCs. CIP2A was phosphorylated by Plk1 at S904, which targets CIP2A to MTOCs and facilitates MTOC organization with CEP192. Our results suggest that CIP2A acts as a scaffold for CEP192-mediated MTOC assembly by recruiting Plk1 and aurora A during meiotic maturation in mouse oocytes.

MASTL inhibition promotes mitotic catastrophe through PP2A activation to inhibit cancer growth and radioresistance in breast cancer cells.

BACKGROUND: Although MASTL (microtubule-associated serine/threonine kinase-like) is a key mitotic kinase that regulates mitotic progression through the inactivation of tumor suppressor protein phosphatase 2A (PP2A), the antitumor mechanism of MASTL targeting in cancer cells is still unclear. METHODS: MASTL expression was evaluated by using breast cancer tissue microarrays and public cancer databases. The effects of MASTL depletion with siRNAs were evaluated in various breast cancer cells or normal cells. Various methods, including cell viability, cell cycle, soft agar, immunoblotting, immunofluorescence, PP2A activity, live image, and sphere forming assay, were used in this study. RESULTS: This study showed the oncosuppressive mechanism of MASTL targeting that promotes mitotic catastrophe through PP2A activation selectively in breast cancer cells. MASTL expression was closely associated with tumor progression and poor prognosis in breast cancer. The depletion of MASTL reduced the oncogenic properties of breast cancer cells with high MASTL expression, but did not affect the viability of non-transformed normal cells with low MASTL expression. With regard to the underlying mechanism, we found that MASTL inhibition caused mitotic catastrophe through PP2A activation in breast cancer cells. Furthermore, MASTL depletion enhanced the radiosensitivity of breast cancer cells with increased PP2A activity. Notably, MASTL depletion dramatically reduced the formation of radioresistant breast cancer stem cells in response to irradiation. CONCLUSION: Our data suggested that MASTL inhibition promoted mitotic catastrophe through PP2A activation, which led to the inhibition of cancer cell growth and a reversal of radioresistance in breast cancer cells.

Helicobacter pylori HP0425 Targets the Nucleus with DNase I-Like Activity.

BACKGROUND AND AIMS: Nuclear targeting of bacterial proteins has a significant impact on host cell pathology. Helicobacter pylori have many nuclear targeting proteins that translocate into the nucleus of host cells. H. pylori HP0425, annotated as hypothetical, has a nuclear localization signal (NLS) sequence, but its function has not been demonstrated. The aim of this experiment was to address the nuclear translocation of HP0425 and determine the effect of HP0425 pathology on host cells. MATERIALS AND METHODS: To investigate the nuclear localization of HP0425, it was expressed in AGS and MKN-1 cells as a GFP fusion protein (pEGFP-HP0425), and its localization was analyzed by confocal microscopy. Recombinant HP0425 (rHP0425) protein was overproduced as a GST fusion protein in Escherichia coli and purified by glutathione-affinity column chromatography. Purified rHP0425 was examined for cytotoxicity and DNase activity. RESULTS: The pEGFP-HP0425 fluorescence was expressed in the nucleus and cytosol fraction of cells, while it was localized in the cytoplasm in the negative control. This protein exhibited DNase activity under various conditions, with the highest DNase activity in the presence of manganese. In addition, the rHP0425 protein efficiently decreased cell viability in a concentration-dependent manner. CONCLUSIONS: These results suggest that HP0425 carrying a nuclear localization signal sequence translocates into the nucleus of host cells and degrades genomic DNA by DNase I-like enzymatic activity, which is a new pathogenic strategy of H. pylori in the host.

Dynamic alterations in PD-1/PD-L1 expression level and immune cell profiles based on radiation response status in mouse tumor model.

Introduction: Based on the immunologic effects of anti-cancer treatment and their therapeutic implications, we evaluated radiotherapy (RT)-induced dynamic alterations in programmed death-1 (PD-1)/PD ligand-1 (PD-L1) expression profiles. Methods: Local RT with 2 Gy × 5 or 7.5 Gy × 1 was administered to the CT26 mouse model. Thereafter, tumors were resected and evaluated at the following predefined timepoints according to radiation response status: baseline, early (immediately after RT), middle (beginning of tumor shrinkage), late (stable status with RT effect), and progression (tumor regrowth). PD-1/PD-L1 activity and related immune cell profiles were quantitatively assessed. Results: RT upregulated PD-L1 expression in tumor cells from the middle to late phase; however, the levels subsequently decreased to levels comparable to baseline in the progression phase. RT with 2 Gy × 5 induced a higher frequency of PD-L1+ myeloid-derived suppressor cells, with a lesser degree of tumor regression, compared to 7.5 Gy. The proportion of PD-1+ and interferon (IFN)-γ+CD8α T cells continued to increase. The frequency of splenic PD-1+CD8+ T cells was markedly elevated, and was sustained longer with 2 Gy × 5. Based on the transcriptomic data, RT stimulated the transcription of immune-related genes, leading to sequentially altered patterns. Discussion: The dynamic alterations in PD-1/PD-L1 expression level were observed according to the time phases of tumor regression. This study suggests the influence of tumor cell killing and radiation dosing strategy on the tumor immune microenvironment.

miR-550a-3-5p acts as a tumor suppressor and reverses BRAF inhibitor resistance through the direct targeting of YAP.

Although evidence has emerged to suggest that YAP overexpression is a crucial factor for tumor progression and resistance to targeted drugs in multiple cancers, the miRNA-mediated YAP regulation is still unclear. Here we show that the novel miR-550a-3-5p acts as a tumor suppressor and reverses BRAF inhibitor resistance through the direct targeting of YAP. Our data showed that the miR-550a-3-5p suppressed cell proliferation, metastasis, and tumor sphere formation through the direct inhibition of YAP and its oncogenic pathway in various cancer cell types. In addition, we showed that the YAP signature was associated with poor survival of colon cancer and identified an inverse correlation between miR-550a-3-5p and YAP in colon cancer tissues. Interestingly, this inverse correlation was regulated in a density-dependent manner. Furthermore, high levels of miR-550a-3-5p were associated with a good prognosis of esophageal cancer, which was suggestive of the clinical relevance of miR-550a-3-5p-mediated YAP regulation in multiple cancers. Importantly, we demonstrated that miR-550a-3-5p treatment sensitized vemurafenib-resistant colon and melanoma cells through YAP inhibition with reduced AKT activity. Moreover, the tumor-suppressive activity of miR-550a-3-5p and its sensitization effect for vemurafenib resistance were also observed in tumor xenograft models. Collectively, our data suggest that miR-550a-3-5p acts as a tumor suppressor through the targeting of oncogenic YAP and may be a new therapeutic tool for YAP-mediated BRAF inhibitor resistance in BRAF-mutant cancer cells.

Centrosome Clustering Is a Tumor-selective Target for the Improvement of Radiotherapy in Breast Cancer Cells.

BACKGROUND/AIM: Owing to the frequent observation of centrosome amplification in human cancers, cancer cells have a unique mechanism to suppress detrimental multipolar division by clustering multiple centrosomes into two functional spindle poles, known as centrosome clustering. This study investigated whether inhibition of centrosome clustering enhances the radiation sensitivity of breast cancer cells. MATERIALS AND METHODS: In this study, inhibition of centrosome clustering was examined by using various centrosome-declustering agents and KIFC1 siRNA in three breast cancer cell lines and two normal fibroblast cell lines. The combination effect of radiation and centrosome declustering was evaluated by cell viability, clonogenic, immunofluorescence assay. RESULTS: This study showed that targeting centrosome clustering enhanced the efficacy of radiotherapy of breast cancer cells with less damage to normal cells. Ionizing radiation induced centrosome amplification in breast cancer cells, but not in normal fibroblast cells. Notably, we showed that centrosome declustering efficiently radiosensitized the centrosome-amplified breast cancer cells through induction of multipolar spindles but did not affect the viability of normal fibroblasts in response to irradiation. Furthermore, KIFC1 mediated the radiosensitivity of the centrosome-amplified breast cancer cells. CONCLUSION: Our data provided the first evidence that centrosome clustering is a tumor-selective target for the improvement of radiotherapy in breast cancer cells.

Antihelminthic drug niclosamide inhibits CIP2A and reactivates tumor suppressor protein phosphatase 2A in non-small cell lung cancer cells.

Protein phosphatase 2A (PP2A) is a critical tumor suppressor complex responsible for the inactivation of various oncogenes. Recently, PP2A reactivation has emerged asan anticancer strategy. Cancerous inhibitor of protein phosphatase 2A (CIP2A), an endogenous inhibitor of PP2A, is upregulated in many cancer cells, including non-small cell lung cancer (NSCLC) cells. We demonstrated that the antihelminthic drug niclosamide inhibited the expression of CIP2A and reactivated the tumor suppressor PP2A in NSCLC cells. We performed a drug-repurposing screen and identified niclosamide asa CIP2A suppressor in NSCLC cells. Niclosamide inhibited cell proliferation, colony formation, and tumor sphere formation, and induced mitochondrial dysfunction through increased mitochondrial ROS production in NSCLC cells; however, these effects were rescued by CIP2A overexpression, which indicated that the antitumor activity of niclosamide was dependent on CIP2A. We found that niclosamide increased PP2A activity through CIP2A inhibition, which reduced the phosphorylation of several oncogenic proteins. Moreover, we found that a niclosamide analog inhibited CIP2A expression and increased PP2A activity in several types of NSCLC cells. Finally, we showed that other well-known PP2A activators, including forskolin and FTY720, did not inhibit CIP2A and that their activities were not dependent on CIP2A. Collectively, our data suggested that niclosamide effectively suppressed CIP2A expression and subsequently activated PP2A in NSCLC cells. This provided strong evidence for the potential use of niclosamide asa PP2A-activating drug in the clinical treatment of NSCLC.

ERp57 modulates STAT3 activity in radioresistant laryngeal cancer cells and serves as a prognostic marker for laryngeal cancer.

Although targeting radioresistant tumor cells is essential for enhancing the efficacy of radiotherapy, the signals activated in resistant tumors are still unclear. This study shows that ERp57 contributes to radioresistance of laryngeal cancer by activating STAT3. Increased ERp57 was associated with the radioresistant phenotype of laryngeal cancer cells. Interestingly, increased interaction between ERp57 and STAT3 was observed in radioresistant cells, compared to the control cells. This physical complex is required for the activation of STAT3 in the radioresistant cells. Among STAT3-regulatory genes, Mcl-1 was predominantly regulated by ERp57. Inhibition of STAT3 activity with a chemical inhibitor or siRNA-mediated depletion of Mcl-1 sensitized radioresistant cells to irradiation, suggesting that the ERp57-STAT3-Mcl-1 axis regulates radioresistance of laryngeal cancer cells. Furthermore, we observed a positive correlation between ERp57 and phosphorylated STAT3 or Mcl-1 and in vivo interactions between ERp57 and STAT3 in human laryngeal cancer. Importantly, we also found that increased ERp57-STAT3 complex was associated with poor prognosis in human laryngeal cancer, indicating the prognostic role of ERp57-STAT3 regulation. Overall, our data suggest that ERp57-STAT3 regulation functions in radioresistance of laryngeal cancer, and targeting the ERp57-STAT3 pathway might be important for enhancing the efficacy of radiotherapy in human laryngeal cancer.