Anti-Melanoma Activities of Haspin Inhibitor CHR-6494 Deployed as a Single Agent or in a Synergistic Combination with MEK Inhibitor

Haspin balances the ratio of asymmetric cell division through Wnt5a and regulates cell fate decisions in mouse embryonic stem cells

Many different types of stem cells utilize asymmetric cell division (ACD) to produce two daughter cells with distinct fates. Haspin-catalyzed phosphorylation of histone H3 at Thr3 (H3T3ph) plays important roles during mitosis, including ACD in stem cells. However, whether and how Haspin functions in ACD regulation remains unclear. Here, we report that Haspin knockout (Haspin-KO) mouse embryonic stem cells (mESCs) had increased ratio of ACD, which cumulatively regulates cell fate decisions. Furthermore, Wnt5a is significantly downregulated due to decreased Pax2 in Haspin-KO mESCs. Wnt5a knockdown mESCs phenocopied Haspin-KO cells while overexpression of Wnt5a in Haspin-KO cells rescued disproportionated ACD. Collectively, Haspin is indispensable for mESCs to maintain a balanced ratio of ACD, which is essential for normal development and homeostasis.

Knockdown of GSG2 inhibits the development and progression of non-small cell lung cancer in vitro and in vivo

Lung cancer has been recognized as the most common malignant neoplasm of the respiratory system with extremely high morbidity, among which non-small cell lung cancer (NSCLC) accounts for the majority. Many published literatures have revealed the roles of GSG2 in the progression of ovarian cancer, bladder cancer and breast cancer. However, there were no reports on the relationship between GSG2 and NSCLC. Herein, GSG2 was identified as a potential tumor promoter in NSCLC development, whose abundant expression was observed in NSCLC tissues compared with adjacent nonmalignant tissues and statistically correlated with more advanced tumor stage, more malignant grade and higher risk of lymphatic metastasis. Subsequent in vitro loss-of-function experiments indicated that GSG2 depletion could arrest cell cycle and suppress cell proliferation and migration while enhancing cell apoptosis. At the same time, the suppressive effects of GSG2 depletion on NSCLC development were verified by in vivo experiments. In conclusion, the current study identified GSG2 as a tumor promoter in development and progression of NSCLC, which could work as a novel therapeutic target for NSCLC.

Function and inhibition of Haspin kinase: targeting multiple cancer therapies by antimitosis

Objectives

Haploid germ cell-specific nuclear protein kinase (Haspin) is a serine/threonine kinase as an atypical kinase, which is structurally distinct from conventional protein kinases.

Key findings

Functionally, Haspin is involved in important cell cycle progression, particularly in critical mitosis regulating centromeric sister chromatid cohesion during prophase and prometaphase, and subsequently ensuring proper chromosome alignment during metaphase and the normal chromosome segregation during anaphase. However, increasing evidence has demonstrated that Haspin is significantly upregulated in a variety of cancer cells in addition to normal proliferating somatic cells. Its knockdown or small molecule inhibition could prevent cancer cell growth and induce apoptosis by disrupting the regular mitotic progression. Given the specificity of its expressed tissues or cells and the uniqueness of its current known substrate, Haspin can be a promising target against cancer. Consequently, selective synthetic and natural inhibitors of Haspin have been widely developed to determine their inhibitory power for various cancer cells in vivo and in vitro.

Summary

Here our perspective includes a comprehensive review of the roles and structure of Haspin, its relatively potent and selective inhibitors and Haspin’s preliminary studies in a variety of cancers.

Knockdown of GSG2 Suppresses the Progression of Colorectal Cancer Cells

Introduction: As a serine/threonine kinase, Haspin (GSG2) has been reportedly associated with the development of malignant tumors. However, few studies have reported the role of GSG2 in colorectal cancer (CRC). Materials and Methods: Based on data from the Oncomine databases, GSG2 was found to be highly expressed in CRC patients' tissues. Therefore, the expression of GSG2 in CRC cell lines was subsequently evaluated. GSG2 loss-of-function experiments were conducted by infection with a lentivirus expressing shRNAs against GSG2. Colony-formation and cell viabilities were assessed using clonogenic and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays, respectively. Migration was assessed using wound-healing and transwell assays. A GSG2 inhibitor experiment was used to investigate the key role of GSG2 in CRC. Immunoprecipitation was used to investigate the interaction between GSG2 and p-H3. In addition, apoptosis was evaluated by quantifying caspase 3/7 activities, and western blot analyses were used to investigate the underlying mechanisms of GSG2 in CRC. Results: GSG2 was found to be highly expressed in CRC tissues and cells. Furthermore, GSG2 knock-down suppressed proliferation, colony formation and invasion, and induced apoptosis in CRC cells. Mechanistically, GSG2 was revealed to regulate Myc, NF-κB, Snail-1, and β-catenin signaling. Conclusion: Collectively, we demonstrate that GSG2 is a potential biomarker of CRC, and that GSG2 interference suppresses the progression of CRC and promotes apoptosis in vitro. These data suggest GSG2 as a putative oncogene, but will require additional in vivo studies to confirm.

Synthesis and biological evaluation of selected 7H-pyrrolo[2,3-d]pyrimidine derivatives as novel CDK9/CyclinT and Haspin inhibitors

Protein kinases, including CDK9/CyclinT and Haspin, are regarded as potential drug targets in cancer therapy. Findings from a previous study suggested 7-azaindole as a privileged scaffold for producing inhibitors of CDK9/CyclinT and Haspin. Inspired by these findings, the current study synthesised and evaluated thirteen (13) C6-substituted 7-azaindole and twenty (20) C4-substituted structurally related 7H-pyrrolo[2,3-d]pyrimidine derivatives against a panel of protein kinases, including CDK9/CyclinT and Haspin. Eleven of the 7H-pyrrolo[2,3-d]pyrimidine derivatives exhibited activity toward CDK9/CyclinT, while 4 of compounds had activity against Haspin. The best CDK9/CyclinT (IC₅₀ of 0.38 μM) and Haspin (IC₅₀ of 0.11 μM) activities were achieved by compounds 7d and 7f, respectively. Hence, these compounds may be valuable starting points for development of new anti-cancer drugs.

Loss of haspin suppresses cancer cell proliferation by interfering with cell cycle progression at multiple stages

Our recent studies have shown that haspin, a protein kinase imperative for mitosis, is engaged in the interphase progression of HeLa and U2OS cancer cells. In this investigation, we employed the Fucci reporter system and time-lapse imaging to examine the impact of haspin gene silencing on cell cycle progressions at a single-cell level. We found that the loss of haspin induced multiple cell cycle defects. Specifically, the S/G2 duration was greatly prolonged by haspin gene depletion or inhibition in synchronous HeLa cells. Haspin gene depletion in asynchronous HeLa and U2OS cells led to a similarly protracted S/G2 phase, followed by mitotic cell death or postmitotic G1 arrest. In addition, haspin deficiency resulted in robust induction of the p21^CIP1/WAF1 checkpoint protein, a target of the p53 activation. Also, co-depleting haspin with either p21 or p53 could rescue U2OS cells from postmitotic G1 arrest and partially restore their proliferation. These results substantiate the haspin's capacity to regulate interphase and mitotic progression, offering a broader antiproliferative potential of haspin loss in cancer cells.

Phosphorylation of H3-Thr3 by Haspin Is Required for Primary Cilia Regulation

Primary cilia are commonly found on most quiescent, terminally differentiated cells and play a major role in the regulation of the cell cycle, cell motility, sensing, and cell–cell communication. Alterations in ciliogenesis and cilia maintenance are causative of several human diseases, collectively known as ciliopathies. A key determinant of primary cilia is the histone deacetylase HDAC6, which regulates their length and resorption and whose distribution is regulated by the death inducer-obliterator 3 (Dido3). Here, we report that the atypical protein kinase Haspin is a key regulator of cilia dynamics. Cells defective in Haspin activity exhibit longer primary cilia and a strong delay in cilia resorption upon cell cycle reentry. We show that Haspin is active in quiescent cells, where it phosphorylates threonine 3 of histone H3, a known mitotic Haspin substrate. Forcing Dido3 detachment from the chromatin prevents Haspin inhibition from impacting cilia dynamics, suggesting that Haspin activity is required for the relocalization of Dido3–HDAC6 to the basal body. Exploiting the zebrafish model, we confirmed the physiological relevance of this mechanism. Our observations shed light on a novel player, Haspin, in the mechanisms that govern the determination of cilia length and the homeostasis of mature cilia.

Design of new disubstituted imidazo[1,2-b]pyridazine derivatives as selective Haspin inhibitors. Synthesis, binding mode and anticancer biological evaluation

Haspin is a mitotic protein kinase required for proper cell division by modulating Aurora B kinase localisation and activity as well as histone phosphorylation. Here a series of imidazopyridazines based on the CHR-6494 and Structure Activity Relationship was established. An assessment of the inhibitory activity of the lead structures on human Haspin and several other protein kinases is presented. The lead structure was rapidly optimised using a combination of crystal structures and effective docking models, with the best inhibitors exhibiting potent inhibitory activity on Haspin with IC₅₀ between 6 and 100 nM in vitro. The developed inhibitors displayed anti-proliferative properties against various human cancer cell lines in 2D and spheroid cultures and significantly inhibited the migration ability of osteosarcoma U-2 OS cells. Notably, we show that our lead compounds are powerful Haspin inhibitors in human cells, and did not block G2/M cell cycle transition due to improved selectivity against CDK1/CyclinB.

Evaluation of the antiproliferative effects of the HASPIN inhibitor CHR-6494 in breast cancer cell lines

HASPIN is a serine/threonine kinase that regulates mitosis by phosphorylating histone H3 at threonine 3. The expression levels of HASPIN in various cancers are associated with tumor malignancy and poor survival, suggesting that HASPIN inhibition may suppress cancer growth. As HASPIN mRNA levels are elevated in human breast cancer tissues compared with adjacent normal tissues, we examined the growth-suppressive effects of CHR-6494, a potent HASPIN inhibitor, in breast cancer cell lines in vitro and in vivo. We found that HASPIN was expressed in breast cancer cells of all molecular subtypes, as well as in immortalized mammary epithelial cells. HASPIN expression levels appeared to be correlated with the cell growth rate but not the molecular subtype of breast cancer. CHR-6494 exhibited potent antiproliferative effects against breast cancer cell lines and immortalized mammary epithelial cells in vitro, but failed to inhibit the growth of MDA-MB-231 xenografted tumors under conditions that have significant effects in a colorectal cancer model. These results imply that CHR-6494 does have antiproliferative effects in some situations, and further drug screening efforts are anticipated to identify more potent and selective HASPIN inhibition for use as an anticancer agent in breast cancer patients.

GSG2 (Haspin) promotes development and progression of bladder cancer through targeting KIF15 (Kinase-12)

Bladder cancer is the most commonly diagnosed malignant tumor in urological system worldwide. The relationship between GSG2 and bladder cancer has not been demonstrated and remains unclear. In this study, it was demonstrated that GSG2 was up-regulated in bladder cancer tissues compared with the normal tissues and its high expression was correlated with more advanced malignant grade and lower survival rate. Further investigations indicated that the overexpression/knockdown of GSG2 could promote/inhibit proliferation, colony formation and migration of bladder cancer cells, while inhibiting/promoting cell apoptosis. Moreover, knockdown of GSG2 could also suppress tumorigenicity of bladder cancer cells in vivo. RNA-sequencing followed by Ingenuity pathway analysis (IPA) was performed for exploring downstream of GSG2 and identified KIF15 as the potential target. Furthermore, our study revealed that knockdown of KIF15 could inhibit development of bladder cancer in vitro, and alleviate the GSG2 overexpression induced promotion of bladder cancer. In conclusion, our study showed, as the first time, GSG2 as a prognostic indicator and tumor promotor for bladder cancer, whose function was carried out probably through the regulation of KIF15.

Knockdown of GSG2 inhibits prostate cancer progression in vitro and in vivo

Prostate cancer (PCa) is the second leading cause of cancer related death among men worldwide. The present study aimed to investigate the role of germ cell-specific gene 2 protein (GSG2), also termed histone H3 phosphorylated by GSG2 at threonine 3, in the development and progression of PCa. GSG2 expression levels in PCa tissues and para carcinoma tissues was detected by immunohistochemistry. The GSG2 knockdown cell model was constructed by lentivirus infec tion, and the knockdown efficiency was verified by qPCR and WB. In addition, the effects of shGSG2 on cell proliferation, colony formation and apoptosis were evaluated by Celigo cell counting assay, Giemsa staining and flow cytometry, respec tively. Tumor development in nude mice was also detected. GSG2 expression was upregulated in PCa tissues and human PCa cell lines PC 3 and DU 145. High expression of GSG2 in tumor samples was associated with progressed tumors. GSG2 knockdown suppressed cell proliferation and colony forma tion, but promoted apoptosis, which was also verified in vivo. The results of the present study revealed that GSG2 upregula tion was associated with PCa progression; GSG2 knockdown inhibited cell proliferation and colony formation and induced apoptosis, and may therefore serve as a potential therapeutic target for PCa therapy.

A Peak of H3T3 Phosphorylation Occurs in Synchrony with Mitosis in Sea Urchin Early Embryos

The sea urchin embryo provides a valuable system to analyse the molecular mechanisms orchestrating cell cycle progression and mitosis in a developmental context. However, although it is known that the regulation of histone activity by post-translational modification plays an important role during cell division, the dynamics and the impact of these modifications have not been characterised in detail in a developing embryo. Using different immuno-detection techniques, we show that the levels of Histone 3 phosphorylation at Threonine 3 oscillate in synchrony with mitosis in Sphaerechinus granularis early embryos. We present, in addition, the results of a pharmacological study aimed at analysing the role of this key histone post-translational modification during sea urchin early development.

HASPIN is involved in the progression of gallbladder carcinoma

BACKGROUND

Gallbladder carcinoma (GBC) is a common malignant tumor of the biliary system, but the current treatment of GBC is unsatisfactory. Therefore, new treatment targets and strategies are urgently needed.

METHODS

The expression of HASPIN in GBC was detected by immunohistochemical staining. HASPIN knockdown cell model was constructed by lentivirus infection, and the infection efficiency of lentivirus and knockdown efficiency of shHASPIN were verified by fluorescence immunoassay, qRT-PCR and Western blot. The effects of HASPIN knockdown on cell proliferation, clone-formation ability and apoptosis were determined by MTT, clone formation assay, flow cytometry and Human Apoptosis Antibody Array in vitro. Besides, the effect of HASPIN knockdown on the growth of GBC solid tumors was demonstrated in vivo.

RESULTS

The expression of HASPIN in GBC was up-regulated and positively correlated with the pathological grade of GBC. ShHASPIN significantly down-regulated the mRNA and protein levels of HASPIN, suggesting that HASPIN knockdown cell model was successfully constructed in vitro. After HASPIN knockdown, the proliferation and clone-formation ability of GBC cells were observably inhibited, the apoptotic levels were markedly increased, and the expression of Caspase 3, IGFBP-5, p21 and sTNF-R1 related to apoptotic pathway was up-regulated. Furthermore, HASPIN knockdown inhibited the growth of GBC in vivo.

CONCLUSION

HASPIN was up-regulated in GBC and played an important role in promoting the progress of GBC.

Bioinformatic Analysis Reveals GSG2 as a Potential Target for Breast Cancer Therapy

Objective

To explore the potential role of GSG2 in breast cancer progression.

Methods

The mRNA expression, DNA copy number and clinical data used in this study were obtained from the TCGA data portal. The copy number variations (CNVs) thresholds were determined according to the set of discrete copy number calls provided by Genomic Identification of Significant Targets in Cancer (GISTIC).

Results

The mRNA expression level of GSG2 in 112 breast cancer tissues was much higher than that in adjacent normal tissues. GSG2 was significantly upregulated in stage II compared with stage I, and there was no differential expression of GSG2 between tumors with or without metastasis. Heterozygous deletion occupied 57.1% of CNVs for GSG2 gene in breast cancer samples. Patients with higher GSG2 expression tended to suffer from poorer prognosis.

Conclusion

Our profiling analysis indicated the overexpression of GSG2 might play an important role in breast cancer development, suggesting that GSG2 could be a new target for breast cancer treatment, making GSG2 inhibitors becoming potential drugs for breast cancer therapy.

Haspin inhibition delays cell cycle progression through interphase in cancer cells

Haspin (Haploid Germ Cell-Specific Nuclear Protein Kinase) is a serine/threonine kinase pertinent to normal mitosis progression and mitotic phosphorylation of histone H3 at threonine 3 in mammalian cells. Different classes of small molecule inhibitors of haspin have been developed and utilized to investigate its mitotic functions. We report herein that applying haspin inhibitor CHR-6494 or 5-ITu at the G1/S boundary could delay mitotic entry in synchronized HeLa and U2OS cells, respectively, following an extended G2 or the S phase. Moreover, late application of haspin inhibitors at S/G2 boundary is sufficient to delay mitotic onset in both cell lines, thereby, indicating a direct effect of haspin on G2/M transition. A prolonged interphase duration is also observed with knockdown of haspin expression in synchronized and asynchronous cells. These results suggest that haspin can regulate cell cycle progression at multiple stages at both interphase and mitosis.

Haspin knockdown can inhibit progression and development of pancreatic cancer in vitro and vivo

BACKGROUND

Pancreatic cancer is one of the most aggressive and lethal malignancies and it is the eighth most common cause of death from cancer worldwide. The purpose of this study was to investigate the role of GSG2 (HASPIN) in the development and progression of pancreatic cancer.

MATERIAL AND METHODS

GSG2 expression was detected by immunohistochemistry in tumor tissue samples, and by qRT-PCR and Western blot assay in human pancreatic cancer cell lines. Cell proliferation was evaluated by MTT assay. Giemsa staining was used for analyzing colony formation. Cell cycle and cell apoptosis were determined using Fluorescence activated Cells Sorting. Wound healing assay and transwell assay were applied for examining cell migration. The molecular mechanism was investigated by human apoptosis antibody array. Tumor-bearing animal model was constructed to verify the effects of GSG2 on pancreatic cancer in vivo.

RESULTS

GSG2 expression was upregulated in pancreatic cancer tissues and human pancreatic cancer cell lines: PANC-1 and SW1990. Higher expression of GSG2 in tumor samples was associated with poorer prognosis. GSG2 knockdown suppressed cell proliferation, colony formation, metastasis and promoted cell apoptosis, which was also verified in vivo. In addition, GSG2 knockdown blocked the cell cycle in G2. It was also found that downregulation of GSG2 inhibited Bcl-2, Bcl-w, cIAP, HSP60 and Livin expression as well as promoted IGFBP-6 expression.

CONCLUSION

This study revealed that GSG2 upregulation was associated with pancreatic cancer progression. GSG2 knockdown inhibited cell proliferation, colony formation and migration, blocked cell cycle at G2 phase, and induced cell apoptosis. Therefore, GSG2 might serve as a potential therapeutic target for pancreatic cancer therapy and a market for prognosis.

3H-pyrazolo[4,3-f]quinoline haspin kinase inhibitors and anticancer properties

Histone modification, a post-translational modification of histones and involving various covalent tags, such as methyl, phosphate and acetate groups, affects gene expression and hence modulates various cellular events, including growth and proliferation. Consequently histone-modifying proteins have become targets for the development of anticancer agents. Thus far, compounds that inhibit the methylation or acetylation of histones have advanced in the clinic, but inhibitors of histone phosphorylation have lagged behind. Haspin is a kinase that phosphorylates histone H3 and is a promising anticancer target. Thus far only a handful of haspin inhibitors have been reported. Using a one-flask Doebner/Povarov reaction, we synthesized a library of compounds that potently inhibit haspin with IC50 values as low as 14 nM. Some of these compounds also inhibited the proliferation of cancer cell lines HCT116, HeLa and A375. The ease of synthesis of the new haspin inhibitors, coupled with their anticancer activities make these compounds interesting leads to develop into therapeutics.

Arctigenin Inhibits Liver Cancer Tumorigenesis by Inhibiting Gankyrin Expression via C/EBPα and PPARα

Burdock (Arctium lappa) is a popular vegetable in China and Japan that is consumed for its general health benefits. The principal active component of burdock is arctigenin, which shows a range of bioactivities in vivo and in vitro. Here, we investigated the potential anti-tumor effects of arctigenin using two human hepatocellular carcinoma (HCC) cell lines, HepG2 and Hep3B, and sought to elucidate its potential mechanisms of action. Our results showed that arctigenin treatment inhibited cell growth in both HepG2 and Hep3B cell lines (IC₅₀ of 4.74 nM for HepG2 cells, and of 59.27 nM for Hep3B cells). In addition, migration, invasion, and colony formation by HepG2 cells were significantly inhibited by arctigenin. By contrast, treatment of Hep3B cells with arctigenin did not alter these parameters. Arctigenin also significantly reduced the levels of gankyrin mRNA and protein in HepG2 cells, but not in Hep3B cells. A luciferase assay indicated that arctigenin targeted the -450 to -400 region of the gankyrin promoter. This region is also the potential binding site for both C/EBPα and PPARα, as predicted and confirmed by an online software analysis and ChIP assay. Additionally, a co-immunoprecipitation (Co-IP) assay showed that binding between C/EBPα and PPARα was increased in the presence of arctigenin. However, arctigenin did not increase the expression of C/EBPα or PPARα protein. A binding screening assay and liquid chromatography-mass spectrometry (LC-MS) were performed to identify the mechanisms by which arctigenin regulates gankyrin expression. The results suggested that arctigenin could directly increase C/EBPα binding to the gankyrin promoter (-432 to -422 region), but did not affect PPARα binding. Expression of gankyrin, C/EBPα, and PPARα were analyzed in tumor tissues of patients using real-time PCR. Both C/EBPα and PPARα showed negative correlations with gankyrin. In tumor-bearing mice, arctigenin had a significant inhibitory effect on HCC growth. In conclusion, our results suggested that arctigenin could inhibit liver cancer growth by directly recruiting C/EBPα to the gankyrin promoter. PPARα subsequently bound to C/EBPα, and both had a negative regulatory effect on gankyrin expression. This study has identified a new mechanism of action of arctigenin against liver cancer growth.