Overexpression Of Plk1 Research Articles

Plk4 regulates centriole duplication in the embryonic development of zebrafish

PLK4 plays a crucial role in centriole duplication, which is essential for maintaining cellular processes such as cell division, cytoskeletal stability, and cilia formation. However, the mechanisms of PLK4 remain incompletely understood, especially in the embryonic development of vertebrate species. In this study, we observed that Plk4 dysfunction led to abnormal embryonic development in zebrafish, characterized by symptoms such as dark and wrinkled skin, microphthalmia, and body axis curvature. In plk4 mutants, defects in centriole duplication led to abnormal cell division, apoptosis, and ciliogenesis defects. Moreover, overexpression of plk4 in zebrafish embryos caused excessive centrosome amplification, disrupting embryonic gastrulation through abnormal cell division and ultimately resulting in embryonic lethality. Furthermore, we identified the "cryptic" polo box (CPB) domain, consisting of two PBs (PB1 and PB2), as the critical centrosome localization domain of Plk4. Surprisingly, overexpression of these two PB domains alone was sufficient to induce embryonic lethality. Additionally, we discovered a truncated form of CPB that localizes to the centrosome without causing defects in embryonic development. Our results demonstrate that Plk4 tightly controls centriole duplication, which is essential for early embryonic development in zebrafish.

A miR-361-5p/ ORC6/ PLK1 axis regulates prostate cancer progression

Prostate cancer (PCa) is the most prevalent malignant tumor of the genitourinary system, and metastatic disease has a significant impact on the prognosis of PCa patients. As a result, knowing the processes of PCa development can help patients achieve better outcomes. Here, we investigated the expression and function of ORC6 in PCa. Our findings indicated that ORC6 was elevated in advanced PCa tissues. Patients with PCa who exhibited high levels of ORC6 had a poor prognosis. Following that, we investigated the function of ORC6 in PCa progression using a variety of functional experiments both in vivo and in vitro, and discovered that ORC6 knockdown inhibited PCa cell proliferation, growth, and migration. Furthermore, RNA-seq was employed to examine the molecular mechanism of PCa progression. The results revealed that ORC6 might promote the expression of PLK1, a serine/threonine kinase in PCa cells. We also discovered that ORC6 as a novel miR-361-5p substrate using database analysis, and miR-361-5p was found to lower ORC6 expression. Additionally, RNA immunoprecipitation (RIP) and luciferase reporter tests revealed that the transcription factor E2F1 could regulate ORC6 expression in PCa cells. PLK1 overexpression or miR-361-5p inhibitor treatment effectively removed the inhibitory effects caused by ORC6 silencing. Notably, our data showed that therapeutically targeting the miR-361-5p/ORC6/PLK1 axis may be a viable therapy option for PCa.

Abstract 7205: PLK1 inhibition overcomes PARP inhibitor resistance in triple-negative breast cancer

Abstract Patients with aggressive breast cancer (BC) subtypes usually do not have favorable prognosis despite improvements in treatment modalities. These cancers remain a major cause of morbidity and mortality in women globally. This has fostered a major effort to discover actionable molecular targets to treat these patients. Polo-like Kinase (PLK1) is one of these molecular targets that are under comprehensive investigation for the treatment of such tumors. However, its role in the pathogenesis of BC from Middle Eastern ethnicity has not been explored. Therefore, we examined the expression of PLK1 protein in a large cohort of more than 1500 Middle Eastern ethnicity BC by immunohistochemistry. Correlation with clinico-pathological parameters and the prognosis was performed. PLK1 overexpression was observed in 27.4% of all BC and was significantly associated with aggressive clinico-pathological markers. The antitumor effect of PLK1 and PARP inhibitors either alone or in combination was tested in two BRCA mutated, and one BRCA proficient TNBC cell lines. We showed that combined inhibition significantly reduced cell survival and induced apoptosis in TNBC cell lines. Furthermore, our data suggest that PLK1 inhibition overcomes PARP inhibitor resistance in TNBC cell lines. These findings would pave the way to explore the future use of PLK1 inhibitors in the clinical setting of PARPi-resistant patients. Citation Format: Abdul K. Siraj, Pratheesh Kumar Poyil, Divya Padmaja, Sandeep Kumar Parvathareddy, Khadija Alobaisi, Rafia Begum, Osama Almalik, Fouad Al-Dayel, Khawla S. Al-Kuraya. PLK1 inhibition overcomes PARP inhibitor resistance in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7205.

Abstract 4611: The co-targeting of PLK1 and FoxM1 contributes to synergistic antitumor effects in PTC

Abstract Polo-like Kinase 1 (PLK1) plays a key role in cell proliferation with vital regulatory functions in mitosis and cell survival. We investigated the expression of PLK1 protein in a large cohort of PTC patient’s samples and explored its functional role in PTC cell lines in vitro and in vivo. PLK1 overexpression was observed in 54% of all PTC and was significantly associated with aggressive clinico-pathological parameter and it was found to be independent prognostic marker for recurrence-free survival. PLK1 inhibition indeed inhibited cell proliferation and induced cell cycle arrest and apoptosis in PTC cell lines. Importantly, silencing of PLK1 decreases the self-renewal ability of spheroids generated from PTC cells. Immunoprecipitation analysis shows that PLK1 binds to FoxM1 and vice versa in vitro. Mechanistically, PLK1 knockdown suppresses FoxM1 expression, whereas inhibition of FoxM1 does not affect PLK1 expression, which suggests that PLK1 acts through the FoxM1 pathway. The combined inhibition of PLK1 with volasertib and FoxM1 with thiostrepton synergistically attenuated PTC cell growth in vitro and in vivo. Our findings suggest that co-targeting of PLK1 and FoxM1 could be a viable therapeutic strategy for treating patients with an aggressive subtype of PTC. Citation Format: Pratheeshkumar Poyil, Abdul K. Siraj, Divya Padmaja, Sandeep Kumar Parvathareddy, Saravanan Thangavel, Saif S. Al-Sobhi, Fouad Al-Dayel, Khawla S. Al-Kuraya. The co-targeting of PLK1 and FoxM1 contributes to synergistic antitumor effects in PTC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4611.

Abstract 5859: PLK1 predicts aggressive behavior in CRC patients and its inhibition reverse chemoresistance in CRC cells

Abstract Polo-like kinase 1 (PLK1) is a serine/threonine-protein kinase, that is involved in multiple stages of cell cycle progression in mammals. Dysregulation of PLK1 has been found in a variety of human cancers and was associated with poor prognoses in various cancers. However, its role in the pathogenesis of CRC from Middle Eastern ethnicity has not yet been explored. Therefore, we examined the expression of PLK1 protein in a large cohort of over 1000 Middle Eastern CRC cases by immunohistochemistry. Correlation with clinico-pathological parameters were performed. PLK1 overexpression was noted in 60.3% (693/1149) CRC cases and was significantly associated with larger tumor size (T3/T4 tumors), lymphnode metastasis, Stage III tumors, MSI-H status and p-ERK1/2 over-expression. Interestingly, on multivariate logistic regression analysis, we found that PLK1 was an independent predictor of lymphnode metastasis. However, no association was noted between PLK1 expression and clinical outcomes (DFS, RFS, OS, CSS). Our in vitro experimentation revealed that CRC cells expressing high levels of PLK1 exhibited resistance to 5-Fu treatment, whereas cells with low PLK1 expression demonstrated sensitivity to the treatment. To explore the role of PLK1 on chemoresistance, we inhibited PLK1 using specific inhibitor, volasertib and we showed that volasertib effectively reversed 5-Fu resistance in these cells. Furthermore, knockdown of PLK1 reduced the progression of epithelial-to-mesenchymal transition (EMT) and the stem cell-like properties in 5-Fu resistant cells, showing the role of PLK1 on inducing EMT and stemness in CRC. Interestingly, the forced expression of PLK1 triggered the activation of the CRAF-MEK-ERK-ZEB1 signaling cascade, whereas its inhibition led to the suppression of this cascade. In addition, we showed that silencing of ERK1/2 reversed the chemoresistance, EMT and stemness of PLK1 expressing CRC cell lines. Our findings underscore the significant role of PLK1 in conferring chemoresistance, and targeting PLK1 could represent a viable therapeutic approach for the treatment of patients with an aggressive subtype of CRC. Citation Format: Divya Padmaja, Maha Al-Rasheed, Pratheesh Kumar Poyil, Abdul K. Siraj, Sandeep Kumar Parvathareddy, Wael Haqawi, Fouad Al-Dayel, Khawla S. Al-Kuraya. PLK1 predicts aggressive behavior in CRC patients and its inhibition reverse chemoresistance in CRC cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 5859.

DLGAP5 promotes lung adenocarcinoma growth via upregulating PLK1 and serves as a therapeutic target

BackgroundHuman discs large-associated protein 5 (DLGAP5) is reported to play a pivotal role in regulating the cell cycle and implicate in tumorigenesis and progression of various cancers. Our current research endeavored to explore the prognostic value, immune implication, biological function and targeting strategy of DLGAP5 in LUAD through approaches including bioinformatics, network pharmacology analysis and experimental study.MethodsMultiple databases, including TCGA, GEO, CPTAC and Human Protein Atlas, were utilized to explore the expression and clinical significance of DLGAP5 in LUAD. The genetic alterations of DLGAP5 were assessed through cBioPortal and COSMIC databases. The relationship between DLGAP5 expression and genetic abnormalities of driver genes in LUAD was analyzed through TIMER2.0 database. CancerSEA database was utilized to explore the function of DLGAP5 in 14 different states in LUAD at single-cell resolution. GDSC database was utilized to analyze the impact of DLGAP5 on IC50 of frequently-used anti-LUAD drugs. CIBERSORT method and TIMER2.0 database was utilized to explore the relationship between DLGAP5 and tumor immune infiltration. Network pharmacology was applied to screen potential DLGAP5 inhibitor. In vitro and in vivo experiments were utilized to evaluate biological function and downstream targets of DLGAP5, and the effect of screened DLGAP5 inhibitor on LUAD growth.ResultsHigh DLGAP5 expression was commonly observed in LUAD and associated with mutation of major driver genes, poor prognosis, high IC50 values of frequently-used anti-LUAD drugs, increasing immune infiltration and elevated immune checkpoint blockade-related genes in LUAD. PLK1 was revealed as a potential DLGAP5 downstream target in LUAD. DLGAP5 overexpression or knockdown significantly promoted or inhibited LUAD cell proliferation and PLK1 expression. PLK1 overexpression well rescued DLGAP5 knockdown-induced cell proliferation inhibition, or vice versa. Furthermore, by virtual screening of an investigational drug library from the DrugBank database, AT9283 was screened and identified as a novel DLGAP5 inhibitor. AT9283 effectively suppressed growth of LUAD cells both in vitro and in vivo. DLGAP5 overexpression significantly reversed AT9283-induced proliferation inhibition. Moreover, AT9283 significantly suppressed DLGAP5 and PLK1 expression, while DLGAP5 overexpression significantly reversed AT9283-induced PLK1 suppression.ConclusionOur research has demonstrated that DLGAP5 is upregulated in LUAD and exhibits a strong correlation with unfavorable prognosis. Furthermore, DLGAP5 assumes a significant function in the regulation of tumor immunity and treatment outcome of immune checkpoint inhibitors. Of note, we found that DLGAP5 promotes cell proliferation of LUAD via upregulating PLK1. Targeting DLGAP5 by AT9283, our newly identified DLGAP5 inhibitor, suppresses LUAD growth. DLGAP5 may become a promising prognostic biomarker and therapeutic target for patients with LUAD.

Prolonged overexpression of PLK4 leads to formation of centriole rosette clusters that are connected via canonical centrosome linker proteins

Centrosome amplification is a hallmark of cancer and PLK4 is one of the responsible factors for cancer associated centrosome amplification. Increased PLK4 levels was also shown to contribute to generation of cells with centriole amplification in mammalian tissues as olfactory neuron progenitor cells. PLK4 overexpression generates centriole rosette (CR) structures which harbor more than two centrioles each. Long term PLK4 overexpression results with centrosome amplification, but the maturation of amplified centrioles in CRs and linking of PLK4 induced amplified centrosomes has not yet been investigated in detail. Here, we show evidence for generation of large clustered centrosomes which have more than 2 centriole rosettes and define these structures as centriole rosette clusters (CRCs) in cells that have high PLK4 levels for 2 consecutive cell cycles. In addition, we show that PLK4 induced CRs follow normal centrosomal maturation processes and generate CRC structures that are inter-connected with canonical centrosomal linker proteins as C-Nap1, Rootletin and Cep68 in the second cell cycle after PLK4 induction. Increased PLK4 levels in cells with C-Nap1 and Rootletin knock-out resulted with distanced CRs and CRCs in interphase, while Nek2 knock-out inhibited separation of CRCs in prometaphase, providing functional evidence for the binding of CRC structures with centrosomal linker proteins. Taken together, these results suggest a cell cycle dependent model for PLK4 induced centrosome amplification which occurs in 2 consecutive cell cycles: (i) CR state in the first cell cycle, and (ii) CRC state in the second cell cycle.

PLK1 and FoxM1 expressions positively correlate in papillary thyroid carcinoma and their combined inhibition results in synergistic anti-tumor effects.

Polo-like kinase 1 (PLK1; also known as serine/threonine-protein kinase PLK1) serves as a central player in cell proliferation, exerting critical regulatory roles in mitotic processes and cell survival. We conducted an analysis of PLK1 protein expression in a large cohort of samples from papillary thyroid carcinoma (PTC) patients and examined its functional significance in PTC cell lines, both in vitro and in vivo. PLK1 overexpression was noted in 54.2% of all PTC and was significantly associated with aggressive clinicopathological parameters; it was also found to be an independent prognostic marker for shorter recurrence-free survival. Given the significant association between PLK1 and forkhead box protein M1 (FoxM1), and their concomitant overexpression in a large proportion of PTC samples, we explored their correlation and their combined inhibitions in PTC in vitro and in vivo. Inhibition of PLK1 expression indeed suppressed cell proliferation, leading to cell cycle arrest and apoptosis in PTC cell lines. Significantly, the downregulation of PLK1 reduced the self-renewal capability of spheroids formed from PTC cells. Immunoprecipitation analysis shows that PLK1 binds to FoxM1 and vice versa in vitro. Mechanistically, PLK1 knockdown suppresses FoxM1 expression, whereas inhibition of FoxM1 does not affect PLK1 expression, which suggests that PLK1 acts through the FoxM1 pathway. The combined treatment of a PLK1 inhibitor (volasertib) and a FoxM1 inhibitor (thiostrepton) demonstrated a synergistic effect in reducing PTC cell growth in vitro and delaying tumor growth in vivo. This study highlights the important role of PLK1 in PTC tumorigenesis and prognosis. It also highlights the synergistic therapeutic potential of dual-targeting PLK1 and FoxM1 in PTC, unveiling a potential innovative therapeutic strategy for managing aggressive forms of PTC.

Potential Therapeutic Targets in Triple-Negative Breast Cancer Based on Gene Regulatory Network Analysis: A Comprehensive Systems Biology Approach.

Background: Triple-negative breast cancer (TNBC) is an aggressive subtype with limited treatment options. This study is aimed at identifying potential therapeutic targets in TNBC using gene regulatory network analysis and a system biology approach. Methods: The GSE38959 dataset was reanalyzed to identify differentially expressed genes (DEGs) in TNBC tissues compared to normal breast samples. Protein-protein interaction networks were constructed, and hub genes were identified. Survival analysis was performed using GEPIA2. Gene regulatory networks were built to identify upstream regulators. Cross-platform verification was conducted using an independent RNA-seq dataset (GSE58135). Expression analysis of prognostic markers in TNBC versus non-TNBC samples was performed using bc-GenExMiner. Results: A total of 943 DEGs were identified in TNBC tissues. CHEK1 and PLK1 were identified as central hub genes, with overexpression correlating with poor prognosis. GABPB1 was identified as the most influential upstream regulator of CHEK1 and PLK1 through gene regulatory network analysis, while JUN exhibited the most interactions among regulators. A total of 302 consistently modulated genes were confirmed through cross-platform verification. The overexpression of CHEK1 and PLK1 in TNBC compared to non-TNBC samples was validated by expression analysis. Conclusion: This study provides insights into the molecular mechanisms of TNBC and suggests CHEK1, PLK1, and their upstream regulators as potential therapeutic targets for TNBC treatment.

The expression and clinical significance of PLK1/p-PLK1 protein in NK/T cell Lymphoma

AimsTo investigate the expression of polo-like kinase 1 protein (PLK1) and its phosphorylation level (p-PLK1) in extranodal NK/T cell lymphoma (NKTCL) and their correlation with clinical characteristics and prognosis.MethodsWe collected 40 cases of NKTCL (referred to as the experimental group), which received diagnoses at the First Affiliated Hospital of Zhengzhou University between January 2018 and October 2022. Concurrently, we assembled a control group, including 20 cases afflicted with nasopharyngeal mucosal lymphoid hyperplasia diseases during the same timeframe. We utilized immunohistochemical techniques to evaluate the levels of PLK1 and p-PLK1 expression in both the experimental and control groups. Subsequently, we conducted an analysis to identify disparities in their expression and explore their relationships with clinical characteristics and patient prognosis.ResultsAmong the 40 NKTCL patients, there were 27 males and 11 females, with a median age of 51 years (range 12–80 years). Compared to the control group, the tissue samples of NKTCL patients exhibited significantly elevated expression levels and active phosphorylation levels of PLK1 (P < 0.05). Correlation analysis of the immunohistochemical H score and Ki-67 positive rate of PLK1 and p-PLK1, revealed a significant positive correlation for both (P < 0.0001, each). No statistically significant differences were observed in the distribution of PLK1 and p-PLK1 expression in NKTCL patients with respect to gender, age, Ann Arbor stage, PINK-E score, B-symptoms, lactate dehydrogenase, β2-microglobulin, blood EBV-DNA, bone marrow invasion, and lymph node metastasis (p > 0.05). Grouping based on PLK1 and p-PLK1 immunohistochemical H-scores revealed that the high expression of PLK1 and p-PLK1 was associated with poor prognosis.ConclusionsThe expression levels and active phosphorylation levels of PLK1 were significantly increased in NK/T cell lymphoma, and patients with overexpression of PLK1 and p-PLK1 had a poorer prognosis.

Loss of the mitochondrial protein SPD-3 elevates PLK-1 levels and dysregulates mitotic events.

In metazoans, Polo-like kinase (PLK1) controls several mitotic events including nuclear envelope breakdown, centrosome maturation, spindle assembly and progression through mitosis. Here we show that a mutation in the mitochondria-localized protein SPD-3 affects mitotic events by inducing elevated levels of PLK-1 in early Caenorhabditis elegans embryos. SPD-3 mutant embryos contain abnormally positioned mitotic chromosomes, show a delay in anaphase onset and asymmetrically disassemble the nuclear lamina. We found that more PLK-1 accumulated on centrosomes, nuclear envelope, nucleoplasm, and chromatin before NEBD, suggesting that PLK-1 overexpression is responsible for some of the observed mitotic phenotypes. In agreement with this, the chromosome positioning defects of the spd-3(oj35) mutant could be rescued by reducing PLK-1 levels. Our data suggests that the mitochondrial SPD-3 protein affects chromosome positioning and nuclear envelope integrity by up-regulating the endogenous levels of PLK-1 during early embryogenesis in C. elegans This finding suggests a novel link between mitochondria and nuclear envelope dynamics and chromosome positioning by increasing the amount of a key mitotic regulator, PLK-1, providing a novel link between mitochondria and mitosis.

Inhibitory Effect of Fingolimod on Head and Neck Squamous Cell Carcinoma and Its Mechanism: Gene Set Enrichment Analysis.

This study aimed to clarify the therapeutic effect of Fingolimod on head and neck squamous cell carcinoma (HNSC) and initially explore its mechanism through data mining, clinical sample analysis and basic experiments. The normalized Enrichment Score (NES) of Fingolimod in tumor tissues was obtained by SwissTargetPrediction and The Cancer Genome Atlas (TCGA) database. IC50 (50% inhibitory concentration) of Fingolimod for HNSC was verified based on the Genomics of Drug Sensitivity in Cancer (GDSC) database. SCC9 cells were cultured in vitro for the application of Fingolimod. Cell proliferation was determined by the Cell Counting Kit-8 (CCK-8). The expression levels of genes were determined by reverse transcription-polymerase chain reaction (RT-PCR). The molecular regulatory mechanism of Fingolimod acting on HNSC was analyzed with WebGestalt. Cyclin expression was determined by Western blot assay. The key targeted genes for Fingolimod against HNSC were screened with the TCGA database and verified in clinical samples. Gene Set Enrichment Analysis (GSEA) showed the highest NES score in HNSC (NES=1.53, P<0.05). GDSC showed the lowest IC50 in Fingolimod SSC9 cells. IC50 calculated by the cell activity detected by CCK8 was 4.34 μmol/L, and RT-PCR showed significantly suppressed expression of proliferation-related gene Ki-67 after adding Fingolimod (P<0.05). Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the targeted genes for Fingolimod were mainly enriched in cell cycle-related pathways. Western blot showed significantly decreased cyclin expression in SSC9 cells after the treatment with Fingolimod (P<0.05). TCGA analysis revealed that PLK1 is a key targeted gene for Fingolimod in the treatment of HNSC. RT-PCR showed the significantly increased activity of SCC9 after over-expressing PLK1, and the increased proliferation and anti-apoptosis abilities (P<0.05), as well as the significantly inhibited expression of Ki-67 and Bcl-2 after adding Fingolimod. Fingolimod can promote the arrest in G0/G1 of SCC9 cells, and PLK1 is a key targeted gene for the treatment of HNSC. Fingolimod can inhibit cell proliferation caused by PLK1 over-expression.

Phase 1 study to determine the safety and efficacy of onvansertib, a novel, oral, PLK1 inhibitor in patients with proliferative chronic myelomonocytic leukemia relapsed/refractory or intolerant to available therapies.

TPS7089 Background: Chronic myelomonocytic leukemia (CMML) is a myelodysplastic/myeloproliferative overlap neoplasm (MDS/MPN) that can be further divided into MD (WBC &lt; 13 x 109/L) and MP (≥13 x 109/L) subtypes. MP-CMML is enriched in RAS pathway mutations ( NRAS, CBL, KRAS, PTPN11 and NF1), has a shorter median survival (19 vs 36 months), has a higher rate of acute myeloid leukemia (AML) transformation (40% vs 10%) and has a unique transcriptomic and epigenetic composition. These RAS pathway mutations promote selective PLK1 overexpression, a mitotic checkpoint kinase. Given the relative inefficacy of hypomethylating agents (HMA) in MP-CMML and previously demonstrated in vitro and in vivo efficacy data for PLK1 inhibition on MP-CMML with RAS pathway mutations, we designed a phase 1 clinical trial testing the safety of onvansertib, a novel, orally bioavailable, PLK1 inhibitor in relapsed/refractory MP-CMML. Methods: This is an investigator-initiated, prospective, open-label, phase I study of onvansertib in MP-CMML relapsed/refractory (RR) or intolerant to existing therapies including HMA and hydroxyurea. The primary endpoint is characterization of safety. Secondary endpoints include efficacy as defined by the 2015 MDS/MPN International Working Group criteria, volumetric spleen response and symptom response via assessment with MPN-SAF-TSS. Inclusion criteria include MP-CMML RR following hydroxyurea or at least 4-cycles of HMA or intolerance of treatment with either, platelets ≥ 20,000/m3 and Cockcroft-Gault creatinine clearance ≥ 60 mL/min/m2. Hydroxyurea may continue for the first 28 days on study. Onvansertib will be given orally on days 1 through 21 of a 28-day cycle with a Bayesian optimal interval design to assess the safety and recommended phase II dose. Exploratory end points include targeting efficacy, impact of PLK1 and KMT2A expression and interactions with ASXL1 and TET2 mutations. Twenty-five patients will be enrolled at Mayo Clinic in Minnesota, with enrollment open since November 2022. Clinical trial information: NCT05549661 .

Abstract 4992: Taxol-elevated PLK1 overcomes BETi-resistant in prostate cancer via triggering phosphorylation-dependent degradation of BRD4

Abstract Background: Bromodomain-containing protein 4 (BRD4) has been widely studied as an attractive therapeutic target of prostate cancer (PCa). Currently, a number of BRD4 inhibitors or degraders have been discovered. However, recent studies revealed that SPOP mutant of prostate cancer patients leads to BRD4 stabilization and resulted in JQ1-resistant. Therefore, to reveal the mechanism underlying BRD4 stability may improve the clinical response rate and efficacy of BRD4-targeted therapy in PCa patients. Methods: To evaluate the level of BRD4 during the mitosis phase, we applied a Confocal microscope and WB. In vitro kinase assay and Mass spectrometry were applied to test the phosphorylation of BRD4 by PLK1. A homemade phosphorylation-specific antibody was used to verify p-BRD4 in PCa cells and a tissue micro-array. A PDX-tumor model was used to evaluate the combination efficacy of Taxol to overcome JQ1-resistant. Result: We found that the level of BRD4 obviously decreased during the mitosis phase of PCa cells. Upon releasing from M-phase arrest, BRD4 level increased along with PLK1 decreasing in PCa cell lines, suggesting PLK1 might be involved in the degradation of BRD4 in the M-phase. We found that PBD domain of PLK1 was responsible for interacting with CTD of BRD4. Enforced overexpression of PLK1 promoted BRD4 dramatically reduced. Reversely, tet-induced depletion or inhibition of PLK1 led to BRD4 stabilization. Furthermore, applying gain or loss of function assay, we found that PLK1 directly phosphorylated BRD4 and triggered its phosphorylation-dependent degradation in M-phase, which was confirmed in clinical samples that high level of PLK1 was negatively correlated with BRD4. Accordingly, we found that overexpression of PLK1 lowered the stabilized BRD4 caused by SPOP mutant in PCa cells and consequently made cells sensitive to JQ1. Intriguingly, upon treated with Taxol, a commonly used medicine for PCa patients, PLK1 level was dramatically elevated as well as p-BRD4 status but total BRD4 downregulated in PCa cells. Moreover, sequential treatment of Taxol and JQ1 resulted in significant inhibition of proliferation, colony formation, and PDX tumor carrying SPOP mutant, indicating application of Taxol overcame JQ-1 resistant. Conclusion: Collectively, our results suggested that PLK1 phosphorylates BRD4 and consequently triggers its phosphorylation-dependent degradation in PCa cells. Sequential treatment of Taxol and JQ1 overcomes SPOP mutant-related BETi-resistant in prostate cancer. Citation Format: Yanquan Zhang, Ka Will Fong, Fengyi Mao, Ruixin Wang, Yifan Kong, Chaohao Li, Jinghui Liu, Zhiguo Li, Derek B. Allison, Dana Napier, Daheng Li, Jinpeng Liu, Chi Wang, Yeqing Zhang, Guangbing Li, Xiaoqi Liu. Taxol-elevated PLK1 overcomes BETi-resistant in prostate cancer via triggering phosphorylation-dependent degradation of BRD4. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4992.

Abstract 3634: Overexpression of PLK1 activates IL4/JAK/STAT6 signaling in prostatic tumor-microenvironment

Abstract The correlation between PLK1 expressions with prostate cancer (PCa) stages was identified by analyzing the transcriptome profile of PLK1 in patients from the Cancer Genome Atlas (TCGA) database, and scoring the protein expression in a clinical tissue microarray (TMA) cohort. Integrating our prostate-specific PLK1 knock-in mouse model, we established an oncogenic role for PLK1 in PCa progression. To elucidate the underlying mechanism, we investigated the impact of PLK1 overexpression on prostatic tumor microenvironment (TME) in vivo. In addition, in vitro co-culture systems with both epithelial cells and macrophages were designed to uncover the regulatory function of PLK1 in macrophage polarization. We found that PLK1 induces phosphorylation of JAK3, activates the JAK/STAT6 pathway in cancer cells, and increases the secretion of IL4, which enables macrophage polarization towards the M2 phenotype in TME—ultimately accelerating PCa development. Finally, pharmaceutical inhibition of STAT6 signaling significantly reverses the PLK1-mediated M2 polarization and, subsequently, inhibits the progression of PCa. Our findings provide clinical and pre-clinical evidence to characterize the role of PLK1 in promoting PCa and novel insights into the regulatory mechanism of PLK1 in the TME. We also provide strong support for the clinical potential of targeting STAT6 for advanced PCa therapy. Citation Format: Ruixin Wang, Xiaoqi Liu. Overexpression of PLK1 activates IL4/JAK/STAT6 signaling in prostatic tumor-microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3634.

Genetic and immune microenvironment characterization of HER2-positive gastric cancer: Their association with response to trastuzumab-based treatment.

We aimed to determine the molecular and immune microenvironment characteristics of HER2-positive gastric cancer (GC) related to the patient's response to first-line trastuzumab-based treatment. Eighty-three cases of HER2-positive advanced gastric adenocarcinoma patients treated with trastuzumab were enrolled. Targeted deep sequencing and transcriptome analysis were performed on selected 21 cases (exploration cohort) along with two post-treatment samples. The results were compared between patients progressed before 6 months (Group 2) and others (Group 1), and were validated by FISH and immunohistochemistry in total cohort. Tumor-infiltrating immune cells were evaluated using RNA sequencing data and multiplex immunohistochemistry. Progression-free survival (PFS) analysis was performed. Group 1 showed frequent amplification of G1/S cell cycle checkpoint-related genes and upregulated KEGG pathways related to cell proliferation. In contrast, Group 2 had more frequent EGFR, HER3, and MET amplification and higher RNA expression in immune-related KEGG pathways than Group 1. In total cohort, significant predictors of better PFS were cell cycle-related including CCNE1 amplification, Cyclin A and PLK1 overexpression, and decreased Cyclin D3 and HER3 expression (p< 0.05), or immune-related including high density of CD3- CD57+ NK cells and PD-L1 combined positive score ≥5 (p< 0.05). The best prognostic predictors were a combination of Cyclin A, Cyclin E, p21, and HER3 (p< 0.001). HER2-positive GC with favorable response to trastuzumab were characterized by cell cycle-related gene alterations and increased CD3- CD57+ NK cell infiltration. These findings would be helpful to the fine modulation of therapeutic strategies for patients with HER2-positive GC.

Abstract P4-08-20: Inhibition of TACC3 blocks the growth of highly aggressive breast cancers with centrosome amplification

Abstract Centrosome amplification (CA) is a hallmark of cancer that is strongly associated with highly aggressive disease and worse clinical outcome. Enhanced mitotic progression via clustering of extra centrosomes is a major coping mechanism utilized by cancer cells with CA that would otherwise undergo mitotic cell death due to formation of multipolar spindles. However, the underlying molecular mechanisms have largely been unexplored. Furthermore, mitosis-targeting inhibitors have mostly been unsuccessful in clinical settings with poor efficacy and severe side effects. Therefore, there is a dire need to uncover novel molecular mechanisms of CA-driven tumor growth and identify therapeutic targets playing key roles not only in mitosis, but also in interphase of cancer cells with CA to achieve durable anti-tumor effect with minimal toxicity. Here, we identified Transforming Acidic Coiled-Coil Containing Protein 3 (TACC3) as a novel CA-directed dependency, driving highly aggressive cell growth by forming distinct functional interactomes during cell cycle progression. We demonstrated, for the first time, that TACC3 interacts with the Kinesin Family Member C1 (KIFC1) via its TACC domain in mitotic cells with CA to promote centrosome clustering (CC) and facilitate mitotic progression. On the other hand, TACC3 interacts with the members of the nucleosome remodeling and deacetylase (NuRD) complex (HDAC2 and MBD2) in the nucleus of interphase cells with CA, thereby suppressing the transcription of key tumor suppressors to facilitate G1/S progression and cell survival. Inhibiting TACC3 in mitotic cells blocks the formation of TACC3/KIFC1 complex, leading to formation of multipolar spindles and activation of spindle assembly checkpoint (SAC)/CDK1/p-Bcl2 axis that ultimately results in mitotic cell death; whereas TACC3 inhibition in interphase cells blocks TACC3/HDAC2/MBD2 complex, leading to enhanced transcription of cyclin-dependent kinase inhibitors (e.g., p21 and p16) and apoptosis regulators (e.g., APAF1), ultimately causing p53-independent G1 arrest and strong apoptosis. Notably, inducing CA by chemical (cytochalasin D) or genomic (PLK4 overexpression or p53 loss) modulations renders cancer cells highly sensitive to TACC3 inhibition, showing the dependency of cells with CA to TACC3. Targeting TACC3 by small molecule inhibitors or CrispR-CAS9-mediated knock-out significantly reduces colony formation ability, inhibits the growth of organoids of patient-derived xenografts (PDXs) with CA, and strongly inhibits tumor growth in breast cancer cell line xenografts and PDXs with CA. Notably, we demonstrated that high CA tumors express much higher levels of TACC3, and high TACC3 expression, in association with its downstream effectors, KIFC1, HDAC2 and MBD2, leads to drastically worse clinical outcome in cancer patients with CA. Altogether, our results show, for the first time, that TACC3 is a multifunctional driver of the growth of the highly aggressive breast tumors with CA and that targeting TACC3 is a promising approach to tackle this aggressive disease. Citation Format: Ozge Saatci, Ozge Akbulut, Metin Cetin, Vitali Sikirzhytski, Ozgur Sahin. Inhibition of TACC3 blocks the growth of highly aggressive breast cancers with centrosome amplification [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-08-20.

CRISPR activation screening in a mouse model for drivers of hepatocellular carcinoma growth and metastasis

Hepatocellular carcinoma (HCC) remains a major cause of cancer-related mortality worldwide. Here we described a genome-wide screen by CRISPR activation (CRISPRa) library invivo for drivers of HCC growth and metastasis. Pathological results showed the cell population formed highly metastatic tumors in lung after being mutagenized with CRISPRa. Invitro validation indicated overexpression of XAGE1B, PLK4, LMO1 and MYADML2 promoted cells proliferation and invasion, and the inhibition suppressed HCC progress. In addition, we reported high MYADML2 protein level exhibited worse overall survival in HCC, which increased significantly in patients over 60 years. Moreover, high MYADML2 reduced the sensitivity to chemotherapeutic drugs. Interestingly, immune cell infiltration analysis showed that the dendritic cells, macrophages, and so forth might play important role in HCC progress. In brief, we provides a roadmap for screening functional genes related to HCC invasion and metastasis invivo, which may provide new potential targets for the treatment of HCC.

Design, synthesis, and biological evaluation of novel pyrimidin-2-amine derivatives as potent PLK4 inhibitors.

Serine/threonine protein kinase PLK4 is a master regulator of centriole duplication, which is significant for maintaining genome integrity. Accordingly, due to the detection of PLK4 overexpression in a variety of cancers, PLK4 has been identified as a candidate anticancer target. Thus, it is a very meaningful to find effective and safe PLK4 inhibitors for the treatment of cancer. However, the reported PLK4 inhibitors are scarce and have potential safety issues. In this study, a series of novel and potent PLK4 inhibitors with an aminopyrimidine core was obtained utilizing the scaffold hopping strategy. The in vitro enzyme activity results showed that compound 8h (PLK4 IC50 = 0.0067 μM) displayed high PLK4 inhibitory activity. In addition, compound 8h exhibited a good plasma stability (t1/2 > 289.1 min), liver microsomal stability (t1/2 > 145 min), and low risk of DDIs. At the cellular level, it presented excellent antiproliferative activity against breast cancer cells. Taken together, these results suggest that compound 8h has potential value in the further research of PLK4-targeted anticancer drugs.

Identification of Important Factors Causing Developmental Arrest in Cloned Pig Embryos by Embryo Biopsy Combined with Microproteomics.

The technique of pig cloning holds great promise for the livestock industry, life science, and biomedicine. However, the prenatal death rate of cloned pig embryos is extremely high, resulting in a very low cloning efficiency. This limits the development and application of pig cloning. In this study, we utilized embryo biopsy combined with microproteomics to identify potential factors causing the developmental arrest in cloned pig embryos. We verified the roles of two potential regulators, PDCD6 and PLK1, in cloned pig embryo development. We found that siRNA-mediated knockdown of PDCD6 reduced mRNA and protein expression levels of the pro-apoptotic gene, CASP3, in cloned pig embryos. PDCD6 knockdown also increased the cleavage rate and blastocyst rate of cloned porcine embryos. Overexpression of PLK1 via mRNA microinjection also improved the cleavage rate of cloned pig embryos. This study provided a new strategy to identify key factors responsible for the developmental defects in cloned pig embryos. It also helped establish new methods to improve pig cloning efficiency, specifically by correcting the expression pattern of PDCD6 and PLK1 in cloned pig embryos.