The CDK7 inhibitor CT7001 (Samuraciclib) targets proliferation pathways to inhibit advanced prostate cancer.

BACKGROUND: Current strategies to inhibit androgen receptor (AR) are circumvented in castration-resistant prostate cancer (CRPC). Cyclin-dependent kinase 7 (CDK7) promotes AR signalling, in addition to established roles in cell cycle and global transcription, providing a rationale for its therapeutic targeting in CRPC. METHODS: The antitumour activity of CT7001, an orally bioavailable CDK7 inhibitor, was investigated across CRPC models in vitro and in xenograft models in vivo. Cell-based assays and transcriptomic analyses of treated xenografts were employed to investigate the mechanisms driving CT7001 activity, alone and in combination with the antiandrogen enzalutamide. RESULTS: CT7001 selectively engages with CDK7 in prostate cancer cells, causing inhibition of proliferation and cell cycle arrest. Activation of p53, induction of apoptosis, and suppression of transcription mediated by full-length and constitutively active AR splice variants contribute to antitumour efficacy in vitro. Oral administration of CT7001 represses growth of CRPC xenografts and significantly augments growth inhibition achieved by enzalutamide. Transcriptome analyses of treated xenografts indicate cell cycle and AR inhibition as the mode of action of CT7001 in vivo. CONCLUSIONS: This study supports CDK7 inhibition as a strategy to target deregulated cell proliferation and demonstrates CT7001 is a promising CRPC therapeutic, alone or in combination with AR-targeting compounds.

AMPK activation protects against prostate cancer by inducing a catabolic cellular state.

Emerging evidence indicates that metabolic dysregulation drives prostate cancer (PCa) progression and metastasis. AMP-activated protein kinase (AMPK) is a master regulator of metabolism, although its role in PCa remains unclear. Here, we show that genetic and pharmacological activation of AMPK provides a protective effect on PCa progression in vivo. We show that AMPK activation induces PGC1α expression, leading to catabolic metabolic reprogramming of PCa cells. This catabolic state is characterized by increased mitochondrial gene expression, increased fatty acid oxidation, decreased lipogenic potential, decreased cell proliferation, and decreased cell invasiveness. Together, these changes inhibit PCa disease progression. Additionally, we identify a gene network involved in cell cycle regulation that is inhibited by AMPK activation. Strikingly, we show a correlation between this gene network and PGC1α gene expression in human PCa. Taken together, our findings support the use of AMPK activators for clinical treatment of PCa to improve patient outcome.

Transcription associated cyclin-dependent kinases as therapeutic targets for prostate cancer.

Transcriptional deregulation has emerged as a hallmark of several cancer types. In metastatic castration-resistant prostate cancer, a stage in which systemic androgen deprivation therapies fail to show clinical benefit, transcriptional addiction to the androgen receptor is maintained in most patients. This has led to increased efforts to find novel therapies that prevent oncogenic transactivation of the androgen receptor. In this context, a group of druggable protein kinases, known as transcription associated cyclin-dependent kinases (tCDKs), show great potential as therapeutic targets. Despite initial reservations about targeting tCDKs due to their ubiquitous and prerequisite nature, preclinical studies showed that selectively inhibiting such kinases could provide sufficient therapeutic window to exert antitumour effects in the absence of systemic toxicity. As a result, several highly specific inhibitors are currently being trialled in solid tumours, including prostate cancer. This article summarises the roles of tCDKs in regulating gene transcription and highlights rationales for their targeting in prostate cancer. It provides an overview of the most recent developments in this therapeutic area, including the most recent clinical advances, and discusses the utility of tCDK inhibitors in combination with established cancer agents.

Adverse effects of cigarette smoke and induction of oxidative stress in cardiomyocytes and vascular endothelium.

Active and passive exposure to cigarette smoke (CS) increases the risk of, and has deleterious effects in, ischaemic heart disease. Exposure to CS increases infarct size in experimental models of coronary occlusion and reperfusion. Among many possible mechanisms for these deleterious effects in intact animals and humans three have more substantial evidence: 1) functional alterations of endothelial cells, neutrophils and platelets; 2) impaired mitochondrial function and energy metabolism caused by toxins in CS, including oxidative free radicals; 3) increased arterial stiffness and vulnerability of the atherosclerotic plaque. In addition to the various pro-mitogenic, carcinogenic and apoptotic pathways thought to be affected and upregulated by CS, a direct necrotic action on cardiomyocytes is also believed to exist. Many, if not all, of these alterations are caused by oxidative stress, either as a direct consequence of inhalation of free radicals, or by induction from the vast range of chemicals present in both the gas and solid phase of tobacco smoke. Here, some of the proposed mechanisms will be reviewed and their impact on the cardiomyocytes and peripheral vasculature discussed.

Donor cell-type specific paracrine effects of cell transplantation for post-infarction heart failure.

Cell transplantation is an emerging therapy for treating post-infarction heart failure. Although the paracrine effect has been proposed to be an important mechanism for the therapeutic benefits, details remain largely unknown. This study compared various aspects of the paracrine effect after transplantation of either bone marrow mononuclear cells (BMC) or skeletal myoblasts (SMB) into the post-infarction chronically failing heart. Three weeks after left coronary artery ligation, adult rats received intramyocardial injection of either BMC, SMB or PBS only. Echocardiography demonstrated that injection of either cell type improved cardiac function compared to PBS injection. Interestingly, BMC injection markedly improved neovascularization in the border areas surrounding infarcts, while SMB injection decreased fibrosis in both the border and remote areas. Injection of either cell type similarly reduced hypertrophy of cardiomyocytes as assessed by cell-size planimetry using isolated cardiomyocytes. Quantitative RT-PCR revealed that, among 15 candidate mediators of paracrine effects studied, Fgf2 and Hgf were upregulated only after BMC injection, while Mmp2 and Timp4 were modulated after SMB injection. Additional investigations of signalling pathways relevant to heart failure by western blotting showed that p38 and STAT3 were temporarily activated after BMC injection, in contrast, ERK1/2 and JNK were activated after SMB injection. There was no difference in activation of Akt, PKD or Smad3 among groups. These data suggest that paracrine effects observed after cell transplantation in post-infarction heart failure were noticeably different between cell types in terms of mediators, signal transductions and consequent effects.

A factor underlying late-phase arrhythmogenicity after cell therapy to the heart: global downregulation of connexin43 in the host myocardium after skeletal myoblast transplantation.

BACKGROUND: Arrhythmia occurrence is a variable but serious concern of cell therapy for treating heart failure. Using a rat postinfarction chronic heart failure model, we compared skeletal myoblast (SMB) with bone marrow cell (BMC) injection to highlight donor cell-specific, late-phase arrhythmogenesis and the underlying factors. METHODS AND RESULTS: SMBs or BMCs derived from male GFP-transgenic rats, or PBS were injected intramyocardially into female rat hearts 3 weeks after coronary artery occlusion. At 28 days after injection, echocardiography showed that the left ventricular ejection fraction was significantly improved in both the SMB and BMC groups, compared to PBS control despite poor graft survival as assessed by PCR for the male-specific gene. Radio-telemetry analysis revealed that the SMB group displayed a higher occurrence of ventricular premature contractions with an elongation of the QRS complex and the hearts were more susceptible to isopreterenol-induced ventricular tachycardia compared to the BMC and PBS groups. Western blot and immunoconfocal analysis showed that the gap junction protein, connexin43, was widely and persistently decreased in the SMB group compared to the other groups. IL-1beta was shown to be upregulated in hearts after SMB injection, and in vitro experiments demonstrated that exposure to IL-1beta caused a decrease in connexin43 and intercellular communication in cultured cardiomyocytes. CONCLUSIONS: Although cell therapy was capable of improving function of the postinfarction chronically failing heart, there was late-phase arrhythmogenicity specific to donor cell type. Global downregulation of connexin43 in the host myocardium was indicated to be an important factor underlying late-phase arrhythmogenicity after SMB transplantation.

Heterogeneic nature of adult cardiac side population cells.

Side population cells have been found in various types of adult tissue including heart and are presumed to be tissue-specific stem/progenitor cells. In the present study, we confirmed the presence of cardiac side population (cSP) cells, which showed both the Hoechst 33342 efflux ability and ABCG2 expression, in adult murine heart. Flow cytometric analysis showed that more than half of cSP cells expressed the endothelial marker VE-cadherin or the smooth muscle markers, alpha-smooth muscle actin and desmin. In addition, immunohistochemical analysis demonstrated that ABCG2(+) cells were mainly localized within vascular walls. Quantitative RT-PCR analysis demonstrated that VE-cadherin(-) cSP cells progressively expressed Nkx2.5 and cardiac troponin T with time in culture. VE-cadherin(-) cSP cells also expressed mesodermal-mesenchymal-associated markers and differentiated into osteocytes and adipocytes. These results highlight the heterogeneic nature of cSP cells, consisting of vascular endothelial cells, smooth muscle cells, and mesenchymal stem/progenitor cells including potential cardiomyogenic cells.

Direct intramyocardial but not intracoronary injection of bone marrow cells induces ventricular arrhythmias in a rat chronic ischemic heart failure model.

BACKGROUND: Therapeutic efficacy of bone marrow (BM) cell injection for treating ischemic chronic heart failure has not been established. In addition, experimental data are lacking on arrhythmia occurrence after BM cell injection. We hypothesized that therapeutic efficacy and arrhythmia occurrence induced by BM cell injection may be affected by the cell delivery route. METHODS AND RESULTS: Three weeks after left coronary artery ligation, wild-type female rats were injected with 1x10(7) mononuclear BM cells derived from green fluorescent protein-transgenic male rats through either a direct intramyocardial or a retrograde intracoronary route. Both intramyocardial and intracoronary injection of BM cells demonstrated similar improvement in left ventricular ejection fraction measured by echocardiography and a similar graft size analyzed by real-time polymerase chain reaction for the Y chromosome-specific Sry gene. Noticeably, intramyocardial injection of BM cells induced frequent ventricular premature contractions (108+/-73 per hour at 7 days after BM cell injection), including multiform, consecutive ventricular premature contractions and ventricular tachycardia for the initial 14 days; intracoronary injection of BM cells and intramyocardial injection of phosphate-buffered saline rarely induced arrhythmias. Immunohistochemistry demonstrated that intramyocardial BM cell injection formed distinct cell clusters containing donor-derived cells and accumulated host-derived inflammatory cells in the infarct border zone, whereas intracoronary BM cell injection provided more homogeneous donor cell dissemination with less inflammation and without disrupting the native myocardial structure. CONCLUSIONS: BM cell injection is able to improve cardiac function in ischemic chronic heart failure but has a risk of arrhythmia occurrence when the intramyocardial route is used. Such arrhythmias may be prevented by using the intracoronary route.