Design and optimization of selective and potent CDK9 inhibitors with flavonoid scaffold for the treatment of acute myeloid leukemia.

Acute myeloid leukemia (AML) is a prevalent hematological tumor associated with a high morbidity and mortality rate. CDK9, functioning as a pivotal transcriptional regulator, facilitates transcriptional elongation through phosphorylation of RNA polymerase II, which further governs the protein levels of Mcl-1 and c-Myc. Therefore, CDK9 has been considered as a promising therapeutic target for AML treatment. Here, we present the design, synthesis, and evaluation of CDK9 inhibitors bearing a flavonoid scaffold. Among them, compound 21a emerged as a highly selective CDK9 inhibitor (IC50 = 6.7 nM), exhibiting over 80-fold selectivity towards most other CDK family members and high kinase selectivity. In Mv4-11 cells, 21a effectively hindered cell proliferation (IC50 = 60 nM) and induced apoptosis by down-regulating Mcl-1 and c-Myc. Notably, 21a demonstrated significant inhibition of tumor growth in the Mv4-11 xenograft tumor model. These findings indicate that compound 21a holds promise as a potential candidate for treating AML.

Echocardiographic evaluation of right heart failure which might be associated with DNA damage response in SU5416-hypoxia induced pulmonary hypertension rat model.

Right heart failure is the leading cause of death in pulmonary hypertension (PH), and echocardiography is a commonly used tool for evaluating the risk hierarchy of PH. However, few studies have explored the dynamic changes in the structural and functional changes of the right heart during the process of PH. Previous studies have found that pulmonary circulation coupling right ventricular adaptation depends on the degree of pressure overload and other factors. In this study, we performed a time-dependent evaluation of right heart functional changes using transthoracic echocardiography in a SU5416 plus hypoxia (SuHx)-induced PH rat model. Rats were examined in 1-, 2-, 4-, and 6-week using right-heart catheterization, cardiac echocardiography, and harvested heart tissue. Our study found that echocardiographic measures of the right ventricle (RV) gradually worsened with the increase of right ventricular systolic pressure, and right heart hypofunction occurred at an earlier stage than pulmonary artery thickening during the development of PH. Furthermore, sarco-endoplasmic reticulum calcium ATPase 2 (SERCA2), a marker of myocardial damage, was highly expressed in week 2 of SuHx-induced PH and had higher levels of expression of γ-H2AX at all timepoints, as well as higher levels of DDR-related proteins p-ATM and p53/p-p53 and p21 in week 4 and week 6. Our study demonstrates that the structure and function of the RV begin to deteriorate with DNA damage and cellular senescence during the early stages of PH development.

Novel biphenyl-based scaffold as potent and selective histone deacetylase 6 (HDAC6) inhibitors: Identification, development and pharmacological evaluation.

A series of novel biphenyl-based scaffold derivatives were identified as selective histone deacetylase 6 (HDAC6) inhibitors through an in-house compound library screening approach. The biological evaluation indicated that most of target compounds exhibited moderate to good inhibitory activity and selectivity against HDAC6. Especially, compound C10 was identified as a potent and highly selective HDACs inhibitor, with HDAC1 IC50 value of 3600 nM, HDAC6 IC50 value of 23 nM, and the HDAC1/6 selectivity index of 157. Moreover, C10 displayed robust anti-proliferative activity, induced cancer cells apoptosis, increased the level of acetylated α-tubulin and inhibited cancer cells migration in vitro. C10 showed significant antitumor efficacy (TGI: 75%) in CT26 colon carcinoma xenograft model in mice with no considerable toxicity in vivo. More importantly, C10 could also activate antitumor immunity so as to synergistically exert antitumor effects in vivo. Overall, our findings have provided a new avenue for design, development and investigation into the mechanism underlying the antitumor efficacy of selective HDAC6 inhibitors.

Revisiting the mechanism of hypoxic pulmonary vasoconstriction using isolated perfused/ventilated mouse lung.

Hypoxic Pulmonary Vasoconstriction (HPV) is an important physiological mechanism of the lungs that matches perfusion to ventilation thus maximizing O2 saturation of the venous blood within the lungs. This study emphasizes on principal pathways in the initiation and modulation of hypoxic pulmonary vasoconstriction with a primary focus on the role of Ca2+ signaling and Ca2+ influx pathways in hypoxic pulmonary vasoconstriction. We used an ex vivo model, isolated perfused/ventilated mouse lung to evaluate hypoxic pulmonary vasoconstriction. Alveolar hypoxia (utilizing a mini ventilator) rapidly and reversibly increased pulmonary arterial pressure due to hypoxic pulmonary vasoconstriction in the isolated perfused/ventilated lung. By applying specific inhibitors for different membrane receptors and ion channels through intrapulmonary perfusion solution in isolated lung, we were able to define the targeted receptors and channels that regulate hypoxic pulmonary vasoconstriction. We show that extracellular Ca2+ or Ca2+ influx through various Ca2+-permeable channels in the plasma membrane is required for hypoxic pulmonary vasoconstriction. Removal of extracellular Ca2+ abolished hypoxic pulmonary vasoconstriction, while blockade of L-type voltage-dependent Ca2+ channels (with nifedipine), non-selective cation channels (with 30 µM SKF-96365), and TRPC6/TRPV1 channels (with 1 µM SAR-7334 and 30 µM capsazepine, respectively) significantly and reversibly inhibited hypoxic pulmonary vasoconstriction. Furthermore, blockers of Ca2+-sensing receptors (by 30 µM NPS2143, an allosteric Ca2+-sensing receptors inhibitor) and Notch (by 30 µM DAPT, a γ-secretase inhibitor) also attenuated hypoxic pulmonary vasoconstriction. These data indicate that Ca2+ influx in pulmonary arterial smooth muscle cells through voltage-dependent, receptor-operated, and store-operated Ca2+ entry pathways all contribute to initiation of hypoxic pulmonary vasoconstriction. The extracellular Ca2+-mediated activation of Ca2+-sensing receptors and the cell-cell interaction via Notch ligands and receptors contribute to the regulation of hypoxic pulmonary vasoconstriction.

Design of wogonin-inspired selective cyclin-dependent kinase 9 (CDK9) inhibitors with potent in vitro and in vivo antitumor activity.

Wogonin, a natural product isolated from the plant Scutellaria baicalensis, has been shown to be a potent and selective inhibitor of CDK9. With the purpose of investigating the activity and selectivity of this chemical scaffold, several series of wogonin derivatives were prepared and screened for CDK9 inhibition and cellular antiproliferative activity. Among these compounds, the drug-like compound 51 showed potent activity against CDK9 (IC50 = 19.9 nM) and MV4-11 cell growth (IC50 = 20 nM). In addition, compound 51 showed much improved physicochemical properties, such as water solubility, compared with the parent compound wogonin. The follow-up studies showed that the compound 51 is selective toward CDK9-overexpressing cancer cells over normal cells. Preliminary mechanism studies on the anticancer effect indicated that 51 inhibited the proliferation of MV4-11 cells via caspase-dependent apoptosis. In addition, highlighted compound 51 showed significant antitumor activity in mouse acute myeloid leukemia (AML) models without producing apparent toxic effects in vivo, which gave us a new tool for further investigation of CDK9-targeted inhibitor as a potential antitumor drug especially for AML.