G1 Cyclins Research Articles

Phase I-II study using DeltaRex-G, a tumor-targeted retrovector encoding a cyclin G1 inhibitor for metastatic carcinoma of breast.

Background: Metastatic breast cancer is associated with a poor prognosis and therefore, innovative therapies are urgently needed. Here, we report on the results of a Phase I-II study using DeltaRex-G for chemotherapy resistant metastatic carcinoma of breast. Patients and Methods: Endpoints: Dose limiting toxicity; Antitumor activity. Eligibility: ≥18years of age, pathologic diagnosis of breast carcinoma, adequate hematologic and organ function. Treatment: Dose escalation of DeltaRex-G 1-4 x 1011cfu intravenously thrice weekly x 4 weeks with 2-week rest period. Treatment cycles repeated if there is ≤ Grade 1 toxicity until disease progression or unacceptable toxicity. Safety: NCI CTCAE v3 for adverse events reporting, vector related testing. Efficacy: RECIST v1.0, International PET criteria and Choi criteria for response, progression free and overall survival. Results: Twenty patients received escalating doses of DeltaRex-G from 1 × 1011cfu to 4 × 1011cfu thrice weekly for 4weeks with a 2-week rest period. Safety: ≥ Grade 3 treatment-related adverse event: pruritic rash (n = 1), no dose limiting toxicity, no replication-competent retrovirus, nor vector-neutralizing antibodies detected. No vector DNA integration was observed in peripheral blood lymphocytes evaluated. Efficacy: by RECIST v1.0: 13 stable disease, 4 progressive disease; tumor control rate 76%; by PET and Choi Criteria: 3 partial responses, 11 stable disease, 3 progressive disease; tumor control rate 82%. Combined median progression free survival by RECIST v1.0, 3.0months; combined median overall survival, 20months; 1-year overall survival rate 83% for Dose Level IV. Biopsy of residual tumor in a participant showed abundant CD8+ killer T-cells and CD45+ macrophages suggesting an innate immune response. Two patients with pure bone metastases had >12-month progression free survival and overall survival and are alive 12years from the start of DeltaRex-G therapy. These patients further received DeltaRex-G + DeltaVax for 6months. Conclusion: Taken together, these data indicate that 1) DeltaRex-G has a distinctively high level of safety and exhibits anti-cancer activity, 2) PET/Choi provide a higher level of sensitivity in detecting early signs of tumor response to DeltaRex-G, 3) DeltaRex-G induced 12- year survival in 2 patients with pure bone metastases who subsequently received DeltaVax immunotherapy, and 4) DeltaRex-G may prove to be a biochemical and/or immune modulator when combined with other cancer therapy/immunotherapy.

Abstract 5559: Exploratory analysis of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) PIK3CA mutated (mut) advanced breast cancer (aBC) treated with taselisib (TAS) and/or fulvestrant (FUL) reveals increased CCNE2 expression with poor outcome to placebo (PBO) + FUL but not TAS + FUL in SANDPIPER

Abstract PIK3CA mutations occur in ~40% of patients (pts) with HR+/HER2- aBC. TAS is a potent and selective β-sparing PI3K inhibitor that has shown modest clinical benefit when combined with FUL endocrine therapy in patients (pts) with PIK3CAmut aBC. To better understand the molecular features associated with response to TAS and/or FUL, we examined the gene expression profiles of archival tissue from pts enrolled in SANDPIPER (NCT02340221). Most patients did not have prior treatment with a CDK4/6i. RNA sequencing was performed on baseline tissue samples from 456 pts with PIK3CAmut tumors. Exploratory biomarker analyses revealed 28 genes associated with worse outcome. Of these, CCNE2 [HR=1.11 (1.04-1.19), p=0.002], RRM2 [HR=1.14 (1.07-1.22), p<0.0001] and TUB4A [HR=1.15 (1.05-1.26), p=0.004] are involved in the regulation of mitotic cell cycle. CCNE2 encodes CYCLIN E2, a G1 cyclin that binds and activates CDK2. Elevated expression of CCNE2 has been associated with poor outcome in ER-positive breast cancer, and has been identified as part of gene signatures that predict disease progression in tamoxifen-resistant breast cancer or advanced breast cancer. Since CCNE2 expression may be a marker of more proliferative tumors, we assessed whether the inclusion of CCNE2 gene expression would add value to a prognostic model that already includes cell cycle as a factor. Analysis of deviance after sequential addition of variables into Coxph models with stratification factors showed that elevated CCNE2 expression is significant, in addition to cell cycle signature scores, for association with worse PFS (likelihood ratio test p = 0.001). When we grouped patients based on CCNE2 expression split by quartile with the highest values (Q4) grouped as CCNE2 high vs lower values (Q1-Q3), we found that the CCNE2 high group does worse in the PBO + FUL treatment arm. Median PFS for CCNE2-high group in the placebo arm was 3.75 months compared to the other groups (log-rank p < 0.0001; PBO, CCNE2-low 7.3 months, TAS, CCNE2-high 7.6 months; TAS, CCNE2-low 7.3 months). A significant statistical interaction was observed between high CCNE2 gene expression and PBO + FUL treatment arm HR=1.51 (1.03-2.20), p=0.04], suggesting that CCNE2 expression may be associated with poor PFS to in 2L ER+/HER2- PIK3CAmut aBC patients that receive PBO + FUL. Our analysis revealed an association between high CCNE2 expression and worse PFS in patients that received PBO + FUL. Further, this association was not observed in the patients that received the combination of TAS+FUL, which may inform future rational combination strategies for the clinical development of PI3K inhibitors in ER+/HER2- PIK3CAmut aBC. Citation Format: Radia M. Johnson, Bonnie Liu, Javier Cortés, Susan Dent, Nadia Harbeck, Ian E. Krop, William Jacot, Robert L. Yauch, Thomas J. Stout, Frauke Schimmoller, Steven Gendreau, Timothy R. Wilson. Exploratory analysis of hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) PIK3CA mutated (mut) advanced breast cancer (aBC) treated with taselisib (TAS) and/or fulvestrant (FUL) reveals increased CCNE2 expression with poor outcome to placebo (PBO) + FUL but not TAS + FUL in SANDPIPER. [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 5559.

Antiproliferative and apoptotic effects of strychnine in human hepatoma HepG2 cells and its mechanism

Hepatocellular carcinoma has the highest prevalence with poor prognosis in liver cancers. Effective treatment strategies are urgently needed to improve the survival of patients with hepatocellular carcinoma. Strychnine, the major active ingredient of the seed of Strychnos nux-vomica L., has been reported to possess an anti-hepatocellular carcinoma function while the underlying mechanism is not fully understood. Here we aim to explore strychnine’s effect on the proliferation and apoptosis of human hepatoma HepG2 cells and clarify mechanism. The cytotoxic activity of strychnine against HepG2 cells was measured. Flow cytometry was used to assess cell apoptosis. The miR-122 expression level was measured via real time quantitative PCR and cyclin G1 and anti-apoptotic proteins including survivin and livin were assessed using Western blot. Strychnine decreased the viability of hepatocellular carcinoma cells and induced their apoptosis in vitro. The levels of livin and survivin were decreased in HepG2 cells after strychnine treatment. By restraining cyclin G1 expression in HepG2 cells, strychnine upregulated liver-specific miR-122 level for the induction of apoptosis. Therefore, strychnine possessed the ability to inhibit cell proliferation and induce apoptosis. Strychnine may be applied for treating liver cancer.

Mutant K-Ras in Pancreatic Cancer: An Insight on the Role of Wild-Type N-Ras and K-Ras-Dependent Cell Cycle Regulation.

The development of K-Ras independence may explain the failure of targeted therapy for pancreatic cancer (PC). In this paper, active N as well as K-Ras was shown in all human cell lines tested. In a cell line dependent on mutant K-Ras, it was shown that depleting K-Ras reduced total Ras activity, while cell lines described as independent had no significant decline in total Ras activity. The knockdown of N-Ras showed it had an important role in controlling the relative level of oxidative metabolism, but only K-Ras depletion caused a decrease in G2 cyclins. Proteasome inhibition reversed this, and other targets of APC/c were also decreased by K-Ras depletion. K-Ras depletion did not cause an increase in ubiquitinated G2 cyclins but instead caused exit from the G2 phase to slow relative to completion of the S-phase, suggesting that the mutant K-Ras may inhibit APC/c prior to anaphase and stabilise G2 cyclins independently of this. We propose that, during tumorigenesis, cancer cells expressing wild-type N-Ras protein are selected because the protein protects cancer cells from the deleterious effects of the cell cycle-independent induction of cyclins by mutant K-Ras. Mutation independence results when N-Ras activity becomes adequate to drive cell division, even in cells where K-Ras is inhibited.

Prognostic significance of microRNA-20a-5p levels which promotes proliferation and invasion by targeting cyclin G2 in small cell lung cancer

MicroRNA-20a-5p (miR-20a-5p) has been shown to function as a tumor promoter factor in several cancers. However, its role in small cell lung cancer (SCLC) remains unclear. In this study, we have made an attempt to measure the tumor tissue levels of miR-20a-5p in patients with SCLC using quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). The biological function of miR-20a-5p in SCLC cells was investigated in vitro and in vivo studies, including cell proliferation, migration assays and tumorigenicity in nude mice. Meanwhile，we conducted the luciferase reporter assay to verify the biological relationship between miR-20a-5p and CCNG2. The expression of miR-20a-5p was significantly upregulated in human SCLC compared to that in normal tissues. Kaplan-Meier analysis indicated that patients with high expression of miR-20a-5p are closely related with the shorter survival of SCLC. Further, multivariate analysis showed that miR-20a-5p was an independent prognostic factor. Increasing miR-20a-5p expression promotes the proliferation, migration and invasion of the NCI-H446 cells in vitro and in vivo. Dual-luciferase reporter gene assay demonstrated that miR-20a-5p directly targets CCNG2. These findings suggest that miR-20a-5p levels might be a novel diagnostic and prognostic marker of SCLC. Inhibiting miR-20a-5p could be a promising therapeutic strategy for SCLC.

Hgc1 Independence of Biofilm Hyphae in Candida albicans.

Biofilm and hypha formation are central to virulence of the fungal pathogen Candida albicans. The G1 cyclin gene HGC1 is required for hypha formation under diverse in vitro and in vivo growth conditions. Hgc1 is required for disseminated infection and is a linchpin in the argument that hyphal morphogenesis itself is required for pathogenicity. We report here that HGC1 is dispensable for hypha formation during biofilm formation both in vitro, under strong inducing conditions, and in vivo, in a mouse oropharyngeal candidiasis model. These findings are validated with two or more C. albicans isolates. Systematic screening of overexpressed cyclin genes indicates that CCN1 and CLN3 can compensate partially for Hgc1 function during biofilm growth. This conclusion is also supported by the severity of the hgc1Δ/Δ ccn1Δ/Δ double mutant biofilm defect. Our results suggest that hypha formation in biofilm is accomplished by combined action of multiple cyclins, not solely by Hgc1. IMPORTANCE The HGC1 gene encodes a cyclin that is required for virulence of the fungal pathogen Candida albicans. It is required to produce the elongated hyphal filaments of free-living planktonic cells that are associated with virulence. Here, we show that HGC1 is not required to produce hyphae in the alternative growth form of a biofilm community. We observe Hgc1-independent hyphae in two infection-relevant situations, biofilm growth in vitro and biofilm-like oropharyngeal infection. Our analysis suggests that hypha formation in the biofilm state reflects combined action of multiple cyclins.

Inflammation and DNA damage: cause, effect or both.

Inflammation is a biological response involving immune cells, blood vessels and mediators induced by endogenous and exogenous stimuli, such as pathogens, damaged cells or chemicals. Unresolved (chronic) inflammation is characterized by the secretion of cytokines that maintain inflammation and redox stress. Mitochondrial or nuclear redox imbalance induces DNA damage, which triggers the DNA damage response (DDR) that is orchestrated by ATM and ATR kinases, which modify gene expression and metabolism and, eventually, establish the senescent phenotype. DDR-mediated senescence is induced by the signalling proteins p53, p16 and p21, which arrest the cell cycle in G1 or G2 and promote cytokine secretion, producing the senescence-associated secretory phenotype. Senescence and inflammation phenotypes are intimately associated, but highly heterogeneous because they vary according to the cell type that is involved. The vicious cycle of inflammation, DNA damage and DDR-mediated senescence, along with the constitutive activation of the immune system, is the core of an evolutionarily conserved circuitry, whicharreststhe cellcycle to reduce the accumulation of mutations generated by DNA replication during redox stress caused by infection or inflammation. Evidence suggests that specific organ dysfunctions in apparently unrelated diseases of autoimmune, rheumatic, degenerative and vascular origins are caused by inflammation resulting from DNA damage-induced senescence.

Anti-proliferative effects of beta-blocker propranolol on human lung cancer and noncancer cells.

Propranolol (PRO) has been recently discovered to possess anti-tumorigenic effects in cancer patients. So, we aimed to enlighten the in vitro effects of propranolol in A549 lung cancer cells and BEAS2B nontumoral lung cells. The gene expression levels of apoptotic proteins; caspases 3, 8, and 9 (CASP3, 8, 9), apoptosis inducing factor (AIF), and DNA damage inducible transcript 3 (DDIT3) and cell cycle regulatory proteins; WEE1 G2 checkpoint kinase (WEE1) and cyclin dependent kinase inhibitor 1A (CDKN1A) were analyzed with quantitative reverse-transcription PCR to assess the effect of PRO on A549 tumor and BEAS2B nontumoral cells. The protein levels of caspase 3 and AIF1 were detected with Western blot. PRO exerted its anti-tumorigenic effects against A549 cells by arresting cell cycle via CDNK1A and by inducing apoptosis via caspase-dependent (CASP3) and -independent pathways (AIF, DDIT3). As to nontumoral BEAS2B cells, PRO decreased the cell viability at a lesser extent compared to tumoral cells. In contrast to tumor cells, PRO reduced the protein levels of CASP3 and AIF1. Notably, at 48th hour of PRO treatment, we observed a sustained expression of elevated DDIT3 mRNA levels at 24h in BEAS2B cells unlike in A549 cells. We suggest that DDIT3 and CDKN1A play a critical role during cell fate decision after PRO treatment by protecting nontumoral cells against apoptosis and by triggering apoptosis in tumor cells. The selective action mechanism of PRO with less cytotoxicity in nontumoral lung cells puts it forward as a promising adjuvant agent in lung cancer therapy (Tab. 1, Fig. 4, Ref. 50). Text in PDF www.elis.sk Keywords: propranolol, BEAS2B, A549, lung cancer, apoptosis, DDIT3.

The Krüppel-like factor 6 represses proliferation and invasion ofcutaneous malignant melanoma.

Cutaneous carcinoma is one ofthemost common neoplasm tumors in theWest. Its incidence rate is one ofthefastest growing tumors in China. TheKrüppel-like factor 6 (KLF6) is alatent tumor suppressor. Decreased KLF6 is related to theoccurrence and progression ofmany cancers in human. Our previous studies have demonstrated that KLF6 was down-regulation in cutaneous malignant melanoma (CMM), and was significant correlated with ulcer, lymph node metastasis and clinical stage, suggesting that KLF6 loss is expected to become abiological indicator ofpoor prognosis in CMM patients. In this research, we would further study thefeatures ofKLF6 in themalignant progression ofCMM. Theexpression ofKLF6 was up-regulated by lentivirus infection containing KLF6, and short hairpin RNA (shRNA) was used for knockdown ofKLF6 in CMM cells. Western blot, RT-qpcr, CCK8 assay, transwell migration assays, wound healing assay and flow cytometry were used to test therole ofKLF6 in theCMM. We found that reduced expression ofKLF6 significantly enhanced proliferation, migration and invasion. Moreover, KLF6 induced CMM cell apoptosis and G1 cycle arrest. Thedecreased KLF6 expression is expected to be abiological indicator ofpoor prognosis in CMM patients.

Cyclin G2 in macrophages triggers CTL-mediated antitumor immunity and antiangiogenesis via interferon-gamma

BackgroundIFN-γ is a key mediator of tumor immunity that can induce macrophage polarization to suppress tumor growth. Cyclin G2 functions as a tumor suppressor in various cancer cells; however, its role in macrophages remains unclear. This study aimed to investigate the role and underlying mechanisms of cyclin G2 in macrophages in vitro and in vivo.MethodsMouse tumor models were used to determine the effect of cyclin G2 in macrophages on tumor growth in vivo following IFN-γ treatment. Immunohistochemistry staining, immunofluorescence staining and flow cytometry were used to evaluate the number of cytotoxic T lymphocytes (CTLs) and blood vessels in the mouse tumors. Moreover, the biological roles of cyclin G2 in macrophages with regard to CTL chemotaxis, cytotoxic function, and vascular endothelial cell tube formation were assessed using in vitro functional experiments. Immunoprecipitation (IP), real-time PCR, and enzyme-linked immunosorbent assays (ELISAs) were conducted to investigate the underlying mechanisms by which cyclin G2 regulates CTLs and vascular endothelial cells.ResultsWe found that cyclin G2 expression was upregulated in macrophages after IFN-γ treatment. Upregulated cyclin G2 inhibited lung and colon cancer growth by increasing the secretion of its downstream effector CXCL9, which promoted CTL chemotaxis and suppressed vascular endothelial cell tube formation. Moreover, cyclin G2 increased CXCL9 mRNA levels by promoting STAT1 nuclear translocation. In addition, cyclin G2 promoted the activation of the STAT1 signaling pathway, which was dependent on PP2Ac.ConclusionsCyclin G2 is upregulated by IFN-γ in macrophages, promotes the secretion of CXCL9 to increase CTL chemotaxis and inhibit angiogenesis to suppress tumor growth. Our findings suggest that targeting cyclin G2 could benefit future immunotherapy.

Three year results of Blessed: Expanded access for DeltaRex-G for an intermediate size population with advanced pancreatic cancer and sarcoma (NCT04091295) and individual patient use of DeltaRex-G for solid malignancies (IND# 19130).

Background: Innovative treatments are urgently needed for metastatic cancer. DeltaRex-G, a tumor-targeted retrovector encoding a dominant-negative/cytocidal cyclin G1 (CCNG1 gene) inhibitor construct-has been tested in over 280 cancer patients worldwide in phase 1, phase 2 studies and compassionate use studies, demonstrating long term (>10years) survivorship in patients with advanced cancers, including pancreatic cancer, osteosarcoma, malignant peripheral nerve sheath tumor, breast cancer, and B-cell lymphoma. Patient and Methods: Endpoints: Survival, response, treatment-related adverse events. Study one is entitled "Blessed: Expanded Access for DeltaRex-G for Advanced Pancreatic Cancer and Sarcoma (NCT04091295)". Study two is entitled "Individual Patient Use of DeltaRex-G for Solid Malignancies (Investigational New Drug#19130). In both studies, patients will receive DeltaRex-G at 1-3 x 10e11cfu i.v. over 30-45min, three x a week until significant disease progression or unacceptable toxicity or death occurs. Results: Seventeen patients were enrolled, nine sarcoma, two pancreatic adenocarcinoma, one non-small cell lung cancer, two breast carcinoma, one prostate cancer, one cholangiocarcinoma and one basal cell carcinoma and actinic keratosis. Three patients were enrolled in Study 1 and 14 patients were enrolled in Study 2. Twelve of 17 enrolled patients were treated with DeltaRex-G monotherapy or in combination with United States Food and Drug Administration-approved cancer therapies. Five patients died before receiving DeltaRex-G. Efficacy Analysis: Of the 12 treated patients, 5 (42%) are alive 15-36months from DeltaRex-G treatment initiation. Two patients with early-stage HR + HER2+ positive or triple receptor negative invasive breast cancer who received DeltaRex-G as adjuvant/first line therapy are alive in complete remission 23 and 16months after DeltaRex-G treatment initiation respectively; three patients with metastatic chordoma, chondrosarcoma and advanced basal cell carcinoma are alive 36, 31, and 15months after DeltaRex-G treatment initiation respectively. Safety Analysis: There were no treatment-related adverse events reported. Conclusion: Taken together, the data suggest that 1) DeltaRex-G may evoke tumor growth stabilization after failing standard chemotherapy, 2) DeltaRex-G may act synergistically with standard chemotherapy/targeted therapies, and 3) Adjuvant/first line therapy with DeltaRex-G for early-stage invasive carcinoma of breast may be authorized by the USFDA when patients refuse to receive toxic chemotherapy.

Cytotoxic and Antimigratory Activity of Retrochalcones from Glycyrrhiza echinata L. on Human Cancer Cells.

Cytotoxic activity-guided fractionation studies on Glycyrrhiza echinata roots led to the isolation of eight compounds (1-8). Chemical structures of the isolates were identified by NMR and MS analysis. Among the tested molecules, retrochalcones namely echinatin (3) (IC50 =23.45-41.83 μM), licochalcone B (4) (IC50 =36.04-39.53 μM) and tetrahydroxylmethoxychalcone (5) (IC50 =7.09-80.81 μM) were the most active ones against PC3, MCF7 and HepG2 cells. Moreover, 5 exhibited selectivity on prostate cancer cells (SI: 5.19). Hoechst staining and Annexin V/PI binding assays as well as cell cycle analysis on the compounds 3 (23 μM) and 5 (5 and 7 μM) demonstrated that these retrochalcones induced apoptosis and significantly suppressed cell cycle in G1 and G2 /M phases. Furthermore, 3 and 5 showed antimigratory effects on PC3 cells by wound healing assay. The results indicated that tested retrochalcones most particularly 5 could be potential anticancer drug candidates that prevent proliferation and migration of cancer cells.

An RNA-seq transcriptome analysis for investigating the anti-lung cancer activity of medicinal Cuscuta chinensis Lam plant.

Cuscuta chinensis Lam. is a traditional medicinal herb used to treat female sterility and male reproductive system disorders. However, the anti-lung cancer properties of Cuscuta chinensis Lam. and possible molecular mechanisms have yet to be explored. Thus, the study’s main purpose was to evaluate in vitro and in vivo anti-lung cancer properties of C. chinensis water extract (CLW) in human lung adenocarcinomas and the underlying molecular mechanism involved. Our results demonstrated that CLW caused a significant inhibition of cell viability and induced G1 cycle arrest in lung cancer cells. Furthermore, RNA-seq transcriptome analysis revealed 602 common genes with a significant expression in A549 and H1650 cells under CLW treatment. Functional enrichment analysis suggested that these common genes regulated by CLW mainly involve lung cancer cell proliferation, metastases and apoptosis processes. In addition, forty-six common genes (> 2-fold change) regulated by CLW in A549 and H1650 cells were selected for further validation. In vitro quantitative real-time PCR results confirmed that twelve genes were up-regulated, and four genes were down-regulated in A549 and H1650 cells. The in vivo experiment demonstrated CLW could significantly decrease tumour volume and tumour weight of mice compared with the control group. Moreover, in vivo quantitative real-time PCR results revealed that C11orf96, FGFBP1, FOSB and NPTX1 genes were up-regulated and EGR1, GBP4 and MAP2K6 genes were down-regulated in tumour tissues compared with the control group. These data strongly suggest that CLW could be developed as an efficacious drug for lung cancer treatment.

Cyclin G1 induces maladaptive proximal tubule cell dedifferentiation and renal fibrosis through CDK5 activation.

Acute kidney injury (AKI) occurs in approximately 13% of hospitalized patients and predisposes patients to chronic kidney disease (CKD) through the AKI-to-CKD transition. Studies from our laboratory and others have demonstrated that maladaptive repair of proximal tubule cells (PTCs), including induction of dedifferentiation, G2/M cell cycle arrest, senescence, and profibrotic cytokine secretion, is a key process promoting AKI-to-CKD transition, kidney fibrosis, and CKD progression. The molecular mechanisms governing maladaptive repair and the relative contribution of dedifferentiation, G2/M arrest, and senescence to CKD remain to be resolved. We identified cyclin G1 (CG1) as a factor upregulated in chronically injured and maladaptively repaired PTCs. We demonstrated that global deletion of CG1 inhibits G2/M arrest and fibrosis. Pharmacological induction of G2/M arrest in CG1-knockout mice, however, did not fully reverse the antifibrotic phenotype. Knockout of CG1 did not alter dedifferentiation and proliferation in the adaptive repair response following AKI. Instead, CG1 specifically promoted the prolonged dedifferentiation of kidney tubule epithelial cells observed in CKD. Mechanistically, CG1 promotes dedifferentiation through activation of cyclin-dependent kinase 5 (CDK5). Deletion of CDK5 in kidney tubule cells did not prevent G2/M arrest but did inhibit dedifferentiation and fibrosis. Thus, CG1 and CDK5 represent a unique pathway that regulates maladaptive, but not adaptive, dedifferentiation, suggesting they could be therapeutic targets for CKD.

Decoupling dedifferentiation and G2/M arrest in kidney fibrosis.

Understanding the cellular mechanisms underlying chronic kidney disease (CKD) progression is required to develop effective therapeutic approaches. In this issue of the JCI, Taguchi, Elias, et al. explore the relationship between cyclin G1 (CG1), an atypical cyclin that induces G2/M proximal tubule cell cycle arrest, and epithelial dedifferentiation during fibrogenesis. While CG1-knockout mice were protected from fibrosis and had reduced G2/M arrest, protection was unexpectedly independent of induction of G2/M arrest. Rather, CG1 drove fibrosis by regulating maladaptive dedifferentiation in a CDK5-dependent mechanism. These findings highlight the importance of maladaptive epithelial dedifferentiation in kidney fibrogenesis and identify CG1/CDK5 signaling as a therapeutic target in CKD progression.

Chenodeoxycholic Acid (CDCA) Promoted Intestinal Epithelial Cell Proliferation by Regulating Cell Cycle Progression and Mitochondrial Biogenesis in IPEC-J2 Cells.

Chenodeoxycholic acid (CDCA), a primary bile acid (BA), has been demonstrated to play an important role as a signaling molecule in various physiological functions. However, the role of CDCA in regulating intestinal epithelial cell (IEC) function remains largely unknown. Herein, porcine intestinal epithelial cells (IPEC-J2) were used as an in vitro model to investigate the effects of CDCA on IEC proliferation and explore the underlying mechanisms. IPEC-J2 cells were treated with CDCA, and flow cytometry and transcriptome analysis were adopted to investigate the effects and potential molecular mechanisms of CDCA on the proliferation of IECs. Our results indicated that adding 50 μmol/L of CDCA in the media significantly increased the proliferation of IPEC-J2 cells. In addition, CDCA treatment also hindered cell apoptosis, increased the proportion of G0/G1 phase cells in the cell cycle progression, reduced intracellular ROS, and MDA levels, and increased mitochondrial membrane potential, antioxidation enzyme activity (T-AOC and CAT), and intracellular ATP level (p < 0.05). RNA-seq results showed that CDCA significantly upregulated the expression of genes related to cell cycle progression (Cyclin-dependent kinase 1 (CDK1), cyclin G2 (CCNG2), cell-cycle progression gene 1 (CCPG1), Bcl-2 interacting protein 5 (BNIP5), etc.) and downregulated the expression of genes related to mitochondrial biogenesis (ND1, ND2, COX3, ATP6, etc.). Further KEGG pathway enrichment analysis showed that CDCA significantly enriched the signaling pathways of DNA replication, cell cycle, and p53. Collectively, this study demonstrated that CDCA could promote IPEC-J2 proliferation by regulating cell cycle progression and mitochondrial function. These findings provide a new strategy for promoting the intestinal health of pigs by regulating intestinal BA metabolism.

DNA Damage Response Signaling Is Crucial for Effective Chikungunya Virus Replication.

Viruses utilize a plethora of strategies to manipulate the host pathways and hijack host machineries for efficient replication. Several DNA and few RNA viruses are reported to interact with proteins involved in DNA damage responses (DDRs). As the DDR pathways have never been explored in alphaviruses, this investigation intended to understand the importance of the DDR pathways in chikungunya virus (CHIKV) infection in vitro, in vivo, and ex vivo models. The study revealed that CHIKV infection activated the Chk2 and Chk1 proteins associated with the DDR signaling pathways in Vero, RAW264.7, and C2C12 cells. The comet assay revealed an increase in DNA damage by 95%. Inhibition of both ATM-ATR kinases by the ATM/ATR kinase inhibitor (AAKi) showed a drastic reduction in the viral particle formation in vitro. Next, the treatment of CHIKV-infected C57BL/6 mice with this drug reduced the disease score substantially with a 93% decrease in the viral load. The same was observed in human peripheral blood mononuclear cell (hPBMC)-derived monocyte-macrophage populations. Additionally, silencing of Chk2 and Chk1 reduced viral progeny formation by 91.2% and 85.5%, respectively. Moreover, CHIKV-nsP2 was found to interact with Chk2 and Chk1 during CHIKV infection. Furthermore, CHIKV infection induced cell cycle arrest in G1 and G2 phases. In conclusion, this work demonstrated for the first time the mechanistic insights regarding the induction of the DDR pathways by CHIKV that might contribute to the designing of effective therapeutics for the control of this virus infection in the future. IMPORTANCE Being intracellular parasites, viruses require several host cell machineries for effectively replicating their genome, along with virus-encoded enzymes. One of the strategies involves hijacking of the DDR pathways. Several DNA and few RNA viruses interact with the cellular proteins involved in the DDR pathways; however, reports regarding the involvement of Chk2 and Chk1 in alphavirus infection are limited. This is the first study to report that modulation of DDR pathways is crucial for effective CHIKV infection. It also reveals an interaction of CHIKV-nsP2 with two crucial host factors, namely, Chk2 and Chk1, for efficient viral infection. Interestingly, CHIKV infection was found to cause DNA damage and arrest the cell cycle in G1 and G2 phases for efficient viral infection. This information might facilitate the development of effective therapeutics for controlling CHIKV infection in the future.

Strategies for Alleviating Tyrosine Kinase Resistance in Acute Myeloid Leukemia By Modulating p53 Signaling Pathway with Small Molecules

Background:FLT3-ITD can be found in up to 30% of acute myeloid leukemia (AML) patients and confers a poor prognosis. While midostaurin and gilteritinib are FDA-approved for these high-risk patients, they only result in a temporary response without transplantation, suggesting the importance of identifying the acquired resistance. Previously, we demonstrated that cabozantinib, an oral multi-target tyrosine kinase inhibitor, was selectively cytotoxic to AML cells with FLT3-ITD (MV4-11 and Molm13). Subsequently, we established cabozantinib-resistant human leukemic MV4-11 derivative (MV4-11-XR) and Molm13 derivative (Molm13-XR) after gradual escalating concentration of cabozantinib incubation from parental MV4-11 (MV4-11-P) and Molm13 (Molm13-P) cells, respectively. Subsequently, cell cytotoxicity assay showed these two cabozantinib-resistant cells were also resistant to quizartinib, sorafenib and gilteritinib. RNA-seq analysis revealed that MV4-11-XR and Molm13-XR cells shared 87 identical differentially down-regulated genes compared to their respective parental cells. Further Metascape for gene enriched pathway analysis demonstrated the most affected was p53 signaling pathway. Aim: To investigate whether modulation with p53 activator RITA or MDM2 inhibitor RG7388 could alleviate the drug resistance and their underlying molecular mechanism. Materials and Methods: Human leukemia MV4-11 and Molm13 cells were used in this study. The differential expression genes (DEGs) were examined using RNA-seq (Illumina NextSeq-500). Metascape enrichment pathway analyses were preformed to predict the biological functions of DEGs. Cabozantinib, RITA, and RG7388 (Idasanutlin) were used. MTS assay was performed to the effects of various drug on cell growth. Western blotting, flow cytometry and quantitative real-time PCR were applied to elucidate potential molecular mechanism. Fluorescent leukemic cell xenografts in zebrafish and high content imaging system were used for investigating the efficacy of various drugs in vivo. Results: The gene expression profile in MV4-11-P and Molm13-P cells was used as a baseline to establish the up- and down-regulated genes in MV4-11-XR and Molm13-XR cells. The FPKM were estimated with the selection criteria of p value <0.05 and [log2 (fold change)] <1 for significantly differential expression for downregulation. We identified a total of 747 DEGs between the MV4-11-P and -XR cells and 407 DEGs between the Molm13-P and -XR cells. Among them, 87 DEGs were shared by these two cohorts. Metascape enrichment analysis revealed that those down-regulated DEGs were enriched in p53-signaling pathway, in line with decreased expression of P53-associated genes, BBC3, CCNG2, CKDN1A, ZMAT3, confirmed by using q-RT-PCR. IGV (Integrative Genomics Viewer) analysis showed that the variant allele frequency of R248W progressed from 57% in MV4-11-P to 100% in MV4-11-XR cells, a similar phenomenon also appeared in P72R (65% to 98%). Microsatellite analysis confirmed the loss of heterozygosity in the TP53 gene of MV4-11-XR. On the other hand, there were not TP53 variants in both Molm13-P and Molm13-XR cells, but increased level of MDM2 in Molm13-XR cells was noted. Further study revealed that p53 activator RITA with 77.6nM could reduce IC50 of cabozantinib from 1026nM to 310.7nM, coupled with increased gene expression and protein levels of BBC3 (PUMA), CCNG2 (cyclin G2), CDKN1A (p21) and ZMAT3. In addition, RITA had synergistic effect with cabozantinib on cell cycle arrest on G2/M phase, increased apoptosis and decreased colony formation and proliferation. On the other hand, MDM2 inhibitor RG7388 reduced the IC50 of cabozantinib from 517nM to 101nM with only 50.6 nM in Molm13-XR cells. Similarly, RG7388 could increase those P53-associated gene expression and protein levels, and had synergistic effect with cabozantinib on cell cycle arrest on G0/G1 phase, increased apoptosis and decreased colony formation and proliferation. In addition, in vivo zebrafish experiment demonstrated that the combination of RG7388 and cabozantinib had a synergistic and significant inhibitory effect compared with single use. Conclusion: These findings suggested that reactivation of p53 is a potential therapeutic option to alleviate drug resistance in FLT3-mutated AML, provided that AML patients are tested for p53 dysfunction, including TP53 mutational status and downregulation.

Ribonuclease Inhibitor 1 (RNH1) Regulates Myeloid Lineage Choice through Cyclin-Dependent Kinase 1

Background: Myelopoiesis is a complex process, it begins with myeloid lineage choice determination in haemopoietic stem cells (HSCs). Still we do not have complete molecular understanding of how myeloid lineage choices were determined. Although transcription factors expression majorly determine the lineage choices at HSCs level, recent study suggest that ratios of total PU.1:GATA1 protein levels are not the central mechanism that initiates HSPC lineage decisions . Further, cell fate commitment is linked to the cell cycle regulation, however whether the cell cycle itself regulates lineage choices in HSCs is not known. Previously, we have published that Ribonuclease inhibitor (RNH1) deletion in mice leads to defect inembryonic erythropoiesis. Here, we report that RNH1 regulates myeloid lineage choice through cyclin-dependent kinase 1 (CDK1) mediated cell cycle regulation. Methods: We have generated hematopoietic-specific conditional knockout mice by crossing Rnh1FL/FL mice with Vav1-iCre and Mx1-Cre mice, respectively. Phenotypic analysis, Bone marrow transplantation (BMT) experiments, cell cycle and CFU assays were performed. To understand molecular mechanism RNA seq, mass spectrometry, confocal microscopy and biochemical studies were performed. Histopathology performed in AML bone marrow biopsies. RNH1 was knocked out in several AML cell lines and analyzed myeloid differentiation and performed CFU assays. Results: Rnh1-deficiency in both Vav1-iCre and Mx1-Cre models resulted in elevated levels of myeloid cells but decreased lymphoid cells and haemoglobin (HGB) levels in peripheral blood. Total bone-marrow (BM) cellularity was similar in wild type (WT) and Rnh1-/- mice. However, the number of erythroid cells and lymphoid cells was significantly decreased, whereas myeloid cells were significantly increased. We analysed the progenitor populations in the BM. In line with increased myelopoiesis phenotype, granulocyte-monocyte progenitor (GMP) cell numbers were increased but common lymphoid progenitor (CLP) and megakaryocyte-erythrocyte progenitor (MEP) cell numbers were decreased. Interestingly, we found increased numbers of long term HSCs (LT-HSCs) and short term HSCs (ST-HSCs) in Rnh1-/- mouse BM, suggesting that RNH1 could affect HSC function. Supporting this, Rnh1-/- HSCs failed to engraft lethally irradiated mice in competitive and non- competitive BMT experiments. Intriguingly, despite increased myelopoiesis in Rnh1-/- mice, conventional myeloid genes that support myelopoiesis were not increased in Rnh1-/- HSCs by RNA-Seq studies. Rather we found increased expression of genes related to cell cycle, kinetochore and DNA damage in Rnh1-/- HSCs. Corroborating this, Rnh1-/- HSCs showed significant increase in G1 cycle phase compared to WT. At the molecular level, we found that RNH1 directly binds to CDK1 and also inhibits CDK1 kinase function. Supporting this, molecular docking studies suggest that RNH1 potentially binds with CDK1. In agreement with this, loss of RNH1 in HSCs increased CDK1 protein levels as well as increased CDK1 phosphorylation at Thr161. Further, CDK1 inhibitor treatment decreased myelopoiesis and rescued erythropoiesis and lymphopoiesis in Rnh1-/- mice. We checked whether RNH1 mediated myelopoiesis is relevant in any disease models and can be targeted. Interestingly, we found increased RNH1 expression in AML patients bone marrow biopsies independent of their genetic mutation. AML blasts have myeloid differentiation arrest and therapies that resolve differentiation arrest represent a powerful treatment strategy. Interestingly, RNH1 deletion in AML cell lines leads to increased expression of the myeloid markers, increased cell death and formed less colonies compared to wild type cells. Summary: Collectively, our studies suggest that loss of RNH1 in HSCs leads to dysregulation in cell cycle through increased CDK1 activity. Dysregulation in cell cycle decreases HSCs stemness and repopulating potential, and influences cell fate decisions by increasing myelopoiesis. Since loss of RNH1 increased myelopoiesis without increase of myeloid transcription factors expression and dependent on CDK1, we call this pathway 'alternative myelopoiesis'. Targeting alternative myelopoiesis could be a potential therapy for AML.

SIRT6 inhibits hypoxia-induced pulmonary arterial smooth muscle cells proliferation via HIF-1α/PDK4 signaling

SIRT6 is an NAD+-dependent protein that plays a vital role in regulating the cell proliferation, differentiation and apoptosis. Abnormal proliferation of pulmonary artery smooth muscle cells (PASMCs) in peripheral vascular is one of the major pathological findings of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). However, whether SIRT6 is involved in hypoxia-induced proliferation of PASMCs and its possible mechanisms remain unknown. In the present study, we found that the expression of SIRT6 was decreased in both hypoxia-induced PAH rats model and HPASMCs. Hypoxia promoted the proliferation of HPASMCs in a time-dependent manner, inhibited the activity of caspase-3 and the production of PDH, increased the activity of LDH, ROS level, mitochondrial membrane potential(MMP) and the expression of HIF-1α and PDK4, which induced glycolysis. SIRT6 over-expression could inhibit the proliferation of HPASMCs and increase the apoptosis rate, impelled the retardation of cell cycle in phase G1. Meanwhile, SIRT6 over-expression reduced LDH activity, the levels of ROS and MMP, which simultaneously increased the production of PDH, the expression of HIF-1α, PDK4, Cyclin D1 and PCNA in hypoxia-induced HPASMCs. Moreover, SIRT6 over-expression inhibited the transcriptional activation of HIF-1α/PDK4 signaling. In addition, SIRT6 knockdown with SIRT6 siRNA exhibited the same effect as hypoxia. Together, our results indicated that SIRT6 was participant in regulating hypoxia-induced imbalance of proliferation and apoptosis of HPASMCs, which was associated with the activation of HIF-1α/PDK4 signaling pathway. Targeting at SIRT6 gene and regulating the downstream metabolism signaling pathway may be a novel strategy for the treatment of hypoxia-induced PAH.