Combined inhibition of PI3Kδ and FLT3 signaling exerts synergistic antitumor activity and overcomes acquired drug resistance in FLT3-activated acute myeloid leukemia

Overcoming adaptive resistance in AML by synergistically targeting FOXO3A-GNG7-mTOR axis with FOXO3A inhibitor Gardenoside and rapamycin

Therapeutic targeting FOXO3A (a forkhead transcription factor) represents a promising strategy to suppress acute myeloid leukemia (AML). However, the effective inhibitors that target FOXO3A are lacking and the adaptive response signaling weakens the cytotoxic effect of FOXO3A depletion on AML cells. Here, we show that FOXO3A deficiency induces a compensatory response involved in the reactive activation of mTOR that leads to signaling rebound and adaptive resistance. Mitochondrial metabolism acts downstream of mTOR to provoke activation of JNK/c-JUN via reactive oxygen species (ROS). At the molecular level, FOXO3A directly binds to the promoter of G protein gamma subunit 7 (GNG7) and preserves its expression, while GNG7 interacts with mTOR and restricts phosphorylated activation of mTOR. Consequently, combinatorial inhibition of FOXO3A and mTOR show a synergistic cytotoxic effect on AML cells and prolongs survival in a mouse model of AML. Through a structure-based virtual screening, we report one potent small-molecule FOXO3A inhibitor (Gardenoside) that exhibits a strong effect of anti-FOXO3A DNA binding. Gardenoside synergizes with rapamycin to substantially reduce tumor burden and extend survival in AML patient-derived xenograft model. These results demonstrate that mTOR can mediate adaptive resistance to FOXO3A inhibition and validate a combinatorial approach for treating AML.

Venetoclax Overcomes Sorafenib Resistance in Acute Myeloid Leukemia by Targeting BCL2

Sorafenib, a kinase inhibitor, has shown promising therapeutic efficacy in a subset of patients with acute myeloid leukemia (AML). However, despite its clinical effectiveness, sorafenib resistance is frequently observed in clinical settings, and the mechanisms underlying this resistance as well as effective strategies to overcome it remain unclear. We examined both single-cell and bulk transcription data in sorafenib-resistant and control AML patients and integrated a sorafenib resistance gene signature to predict the sensitivity of AML cells and the clinical outcomes of AML patients undergoing sorafenib therapy. In addition, our drug sensitivity analysis of scRNA-seq data using deconvolution methods showed that venetoclax was effective in targeting sorafenib-resistant AML cells. Mechanistically, sorafenib was found to activate the JAK-STAT3 pathway and upregulate BCL2 expression in sorafenib-resistant AML cells. This upregulation of BCL2 expression rendered the cells vulnerable to the BCL2 inhibitor venetoclax. In conclusion, we developed a platform to predict sorafenib resistance and clinical outcomes in AML patients after therapy. Our findings suggest that the combination of sorafenib and venetoclax could be an effective therapeutic strategy for AML treatment.

The pathogenesis and development of targeted drugs in acute T lymphoblastic leukaemia

Acute lymphoblastic leukaemia (ALL) is mainly classified into acute T- and B-lymphoblastic leukaemia according to the source of its lymphocytes, thymus and bone. Among them, the incidence of adult T-cell accounts for about 25% of adult acute lymphoblastic leukaemia, but the degree of malignancy is high and the treatment rate and prognosis are poor. At this stage, there are few targeted drugs and the commonly used broad-spectrum chemotherapeutic drugs have poor efficacy and many adverse drug reactions. Understanding and investigating the pathogenesis of T-acute lymphoblastic leukaemia is very important for further developing new targeting drugs and improving existing drugs. Dysregulated signalling pathways are the main aetiological factors of T-acute lymphoblastic leukaemia. They play crucial roles in promoting tumour initiation, progression, drug design and therapy responses. This is primarily because signalling pathways are indispensable for many cellular biological processes, including tumour growth, migration, invasion, metastasis and others. As a result, small molecule inhibitors targeting the major kinase components of the signalling pathway have received a lot of attention and have been developed and evaluated in preclinical models and clinical trials. Already marketed drugs are also being repurposed in combination therapies to further improve efficacy and overcome tumour cell resistance. In this review, we have aimed to examine the latest and most classical signalling pathways in the aetiology of T-acute lymphoblastic leukaemia and shed light on potential targets for novel therapeutic agents to act on.

Selective CDK4/6 inhibition of novel 1,2,3-triazole tethered acridinedione derivatives induces G1/S cell cycle transition arrest via Rb phosphorylation blockade in breast cancer models

CDK4 & CDK6 are essential regulators of initial cell cycle phases and are always considered an exciting choice for anti-cancer therapy. In the present study, we presented the structure-based rational design & synthesis of a new class of 1,2,3-triazole tethered acridinedione derivatives (6a-l) as selective CDK4/6 inhibitors. Title molecules were prepared as a result of the rate-determining reaction between substituted derivatives of 1-Phenyl-1H-1,2,3-triazole-4-carbaldehydes and substituted dimedones, and the molecules were structurally characterized by IR, ¹H,¹³C NMR, and MS spectral data. All molecules were screened for in-vitro cytotoxic potential against a group of human breast tumor cell lines of distinct origin with differential Rb expression status. Out of entire series of conjugated hexahydro acridinediones, 6g showed potent cytotoxic effect against MCF-7, BT-474, and SK-BR3 cell lines with IC₅₀values 0.173 ± 0.037, 0.117 ± 0.025, and 0.136 ± 0.027 μM, respectively. Further, CDK inhibition assays revealed that the compounds 6g and 6h selectively inhibit CDK4/6 over other CDK-parter complexes of the family against the selected cell line group except for MDA-MB468 cells. Furthermore, apoptotic evaluation and cell cycle analysis determined that compound 6g successfully triggered apoptosis in all examined cell lines except MDA-MB468 through blocking G1/S cell cycle transformation. In addition, compound 6g showed the highest in-vitro selectivity towards CDK4/6 inhibition, even compared with Abemaciclib, and it was also proved for favourable in-vivo pharmacokinetic properties in male albino mice. Furthermore, molecule 6g showed promising tumor growth suppression with lower adverse effects in MCF-7 xenograft mice models, which could competently be considered as a novel chemotherapeutic candidate for a further comprehensive preclinical study involving breast cancer therapy.

Genetic biomarkers of drug resistance: A compass of prognosis and targeted therapy in acute myeloid leukemia

Acute myeloid leukemia (AML) is a highly aggressive hematological malignancy with complex heterogenous genetic and biological nature. Thus, prognostic prediction and targeted therapies might contribute to better chemotherapeutic response. However, the emergence of multidrug resistance (MDR) markedly impedes chemotherapeutic efficacy and dictates poor prognosis. Therefore, prior evaluation of chemoresistance is of great importance in therapeutic decision making and prognosis. In recent years, preclinical studies on chemoresistance have unveiled a compendium of underlying molecular basis, which facilitated the development of targetable small molecules. Furthermore, routing genomic sequencing has identified various genomic aberrations driving cellular response during the course of therapeutic treatment through adaptive mechanisms of drug resistance, some of which serve as prognostic biomarkers in risk stratification. However, the underlying mechanisms of MDR have challenged the certainty of the prognostic significance of some mutations. This review aims to provide a comprehensive understanding of the role of MDR in therapeutic decision making and prognostic prediction in AML. We present an updated genetic landscape of the predominant mechanisms of drug resistance with novel targeted therapies and potential prognostic biomarkers from preclinical and clinical chemoresistance studies in AML. We particularly highlight the unfolded protein response (UPR) that has emerged as a critical regulatory pathway in chemoresistance of AML with promising therapeutic horizon. Futhermore, we outline the most prevalent mutations associated with mechanisms of chemoresistance and delineate the future directions to improve the current prognostic tools. The molecular analysis of chemoresistance integrated with genetic profiling will facilitate decision making towards personalized prognostic prediction and enhanced therapeutic efficacy.

Combined inhibition of Notch and FLT3 produces synergistic cytotoxic effects in FLT3/ITD+ acute myeloid leukemia

Internal tandem duplication (ITD) mutations of FMS-like tyrosine kinase-3 (FLT3) are the most frequent genetic alterations in acute myeloid leukemia (AML) and predict a poor prognosis. FLT3 tyrosine kinase inhibitors (TKIs) provide short-term clinical responses, but the long-term prognosis of FLT3/ITD⁺ AML patients remains poor. Notch signaling is important in numerous types of tumors. However, the role of Notch signaling in FLT3/ITD⁺ AML remains to be elucidated. In the current study, we found that Notch signaling was activated upon FLT3-TKI treatment in FLT3/ITD⁺ cell lines and primary cells. As Notch signaling can be blocked by γ-secretase inhibitors (GSIs), we examined the combinatorial antitumor efficacy of FLT3-TKIs and GSIs against FLT3/ITD⁺ AML and explored the underlying molecular mechanisms. As a result, we observed synergistic cytotoxic effects, and the treatment preferentially reduced cell proliferation and induced apoptosis in FLT3/ITD⁺ AML cell lines and in primary AML cells. Furthermore, the combination of FLT3-TKI and GSI eradicated leukemic cells and prolonged survival in an FLT3/ITD⁺ patient-derived xenograft AML model. Mechanistically, differential expression analysis suggested that CXCR3 may be partially responsible for the observed synergy, possibly through ERK signaling. Our findings suggest that combined therapies of FLT3-TKIs with GSI may be exploited as a potential therapeutic strategy to treat FLT3/ITD⁺ AML.

Preclinical characterization of SHR6390, a novel CDK 4/6 inhibitor, in vitro and in human tumor xenograft models

Inhibition of the cyclin‐dependent kinase (CDK) 4/6‐retinoblastoma (RB) pathway is an effective therapeutic strategy against cancer. Here, we performed a preclinical investigation of the antitumor activity of SHR6390, a novel CDK4/6 inhibitor. SHR6390 exhibited potent antiproliferative activity against a wide range of human RB‐positive tumor cells in vitro, and exclusively induced G₁ arrest as well as cellular senescence, with a concomitant reduction in the levels of Ser780‐phosphorylated RB protein. Compared with the well‐known CDK4/6 inhibitor palbociclib, orally administered SHR6390 led to equivalent or improved tumor efficacy against a panel of carcinoma xenografts, and produced marked tumor regression in some models, in association with sustained target inhibition in tumor tissues. Furthermore, SHR6390 overcame resistance to endocrine therapy and HER2‐targeting antibody in ER‐positive and HER2‐positive breast cancer, respectively. Moreover, SHR6390 combined with endocrine therapy exerted remarkable synergistic antitumor activity in ER‐positive breast cancer. Taken together, our findings indicate that SHR6390 is a novel CDK4/6 inhibitor with favorable pharmaceutical properties for use as an anticancer agent.

Silencing of COPB2 inhibits the proliferation of gastric cancer cells and induces apoptosis via suppression of the RTK signaling pathway

Emerging studies have reported that coatomer protein complex subunit β2 (COPB2) is overexpressed in several types of malignant tumor; however, to the best of our knowledge, no studies regarding COPB2 in gastric cancer have been published thus far. Therefore, the present study aimed to determine the significance and function of COPB2 in gastric cancer. COPB2 expression in gastric cancer cell lines was measured using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analysis. In addition, lentivirus-short hairpin RNA (shRNA) COPB2 (Lv-shCOPB2) was generated and used to infect BGC-823 cells to analyze the effects of COPB2 on the cancerous phenotype. The effects of shRNA-mediated COPB2 knockdown on cell proliferation were detected using MTT, 5-bromo-2-deoxyuridine and colony formation assays. In addition, the effects of COPB2 knockdown on apoptosis were analyzed by flow cytometry. Nude mice and fluorescence imaging were used to characterize the regulation of tumor growth in vivo, and qPCR and immunohistochemistry were subsequently conducted to analyze COPB2 expression in xenograft tumor tissues. Furthermore, a receptor tyrosine kinase (RTK) signaling pathway antibody array was used to explore the relevant molecular mechanisms underlying the effects of COPB2 knockdown. The results revealed that COPB2 mRNA was abundantly overexpressed in gastric cancer cell lines, whereas knockdown of COPB2 significantly inhibited cell growth and colony formation ability, and led to increased cell apoptosis in vitro. The tumorigenicity assay revealed that knockdown of COPB2 reduced tumor growth in nude mice, and fluorescence imaging indicated that the total radiant efficiency of mice in the Lv-shCOPB2-infected group was markedly reduced compared with the mice in the Lv-shRNA control-infected group in vivo. The antibody array assay revealed that the levels of phosphorylation in 23 target RTKs were significantly reduced: In conclusion, COPB2 was highly expressed in gastric cancer cell lines, and knockdown suppressed colony formation and promoted cell apoptosis via inhibiting the RTK signaling and its downstream signaling cascade molecules. Therefore, COPB2 may present a valuable target for gene silencing strategy in gastric cancer.

Identification of novel PI3Kδ inhibitors by docking, ADMET prediction and molecular dynamics simulations

BACKGROUND

Phosphoinositide-3-kinase Delta (PI3Kδ) plays a key role in B-cell signal transduction and inhibition of PI3Kδ is confirmed to have clinical benefit in certain types of activation of B-cell malignancies. Virtual screening techniques have been used to discover new molecules for developing novel PI3Kδ inhibitors with little side effects.

METHOD

Computer aided drug design method were used to rapidly screen optimal PI3Kδ inhibitors from the Asinex database. Virtual screening based molecular docking was performed to find novel and potential lead compound targeting PI3Kδ, at first. Subsequently, drug likeness studies were carried out on the retrieved hits to evaluate and analyze their drug like properties such as absorption, distribution, metabolism, excretion, and toxicity (ADMET) for toxicity prediction. Three least toxic compounds were selected for the molecular dynamics (MD) simulations for 30 ns in order to validate its stability inside the active site of PI3Kδ receptor.

RESULTS

Based on the present in silico analysis, two molecules have been identified which occupied the same binding pocket confirming the selection of active site. ASN 16296138 (Glide score: -12.175 kcal/mol, cdocker binding energy: -42.975 kcal/mol and ΔG_bind value: -90.457 kcal/mol) and BAS 00227397 (Glide score: -10.988 kcal/mol, cdocker binding energy: -39.3376 kcal/mol and ΔG_bind value: -81.953 kcal/mol) showed docking affinities comparatively much stronger than those of already reported known inhibitors against PI3Kδ. These two ligand's behaviors also showed consistency during the simulation of protein-ligand complexes for 30000 ps respectively, which is indicative of its stability in the receptor pocket.

CONCLUSION

Compound ASN 16296138 and BAS 00227397 are potential candidates for experimental validation of biological activity against PI3Kδ in future drug discovery studies. This study smoothes the path for the development of novel leads with improved binding properties, high drug likeness, and low toxicity to humans for the treatment of cancer.

FLT3 inhibitors in acute myeloid leukemia

FLT3 mutations are one of the most common findings in acute myeloid leukemia (AML). FLT3 inhibitors have been in active clinical development. Midostaurin as the first-in-class FLT3 inhibitor has been approved for treatment of patients with FLT3-mutated AML. In this review, we summarized the preclinical and clinical studies on new FLT3 inhibitors, including sorafenib, lestaurtinib, sunitinib, tandutinib, quizartinib, midostaurin, gilteritinib, crenolanib, cabozantinib, Sel24-B489, G-749, AMG 925, TTT-3002, and FF-10101. New generation FLT3 inhibitors and combination therapies may overcome resistance to first-generation agents.