Can cyclin-dependent kinase 4/6 inhibitors convert inoperable breast cancer relapse to operability? A case report

BACKGROUND Pathological complete response(pCR) is rare in hormone receptor-positive(HR+)HER2-negative breast cancer(BC) treated with either endocrine therapy(ET) or chemotherapy. Radical resection of locoregional relapse, although potentially curative in some cases, is challenging when the tumor invades critical structures.The oral cyclin-dependent kinase 4/6 inhibitor palbociclib in combination with ET has obtained a significant increase in objective response rates and progression-free survival in patients with advanced BC and is now being evaluated in the neoadjuvant setting. We present a clinical case of a patient with an inoperable locoregional relapse of HR+ HER2-negative BC who experienced p CR after treatment with palbociclib.CASE SUMMARY We report the clinical case of a 60-year-old patient who presented with an inoperable locoregional relapse of HR+, HER2-negative BC 10 years after the diagnosis of the primary tumor. During a routine follow-up visit, breast magnetic resonance imaging and positron emission tomography/computed tomography revealed a 4-cm lesion in the right subclavicular region, infiltrating the chest wall and extending to the subclavian vessels, but without bone or visceral involvement. Treatment was begun with palbociclib plus letrozole, converting the disease to operability over a period of 6 mo. Surgery was performed and a p CR achieved. Of note, during treatment the patient experienced a very uncommon toxicity characterized by burning tongue and glossodynia associated with dysgeusia, paresthesia, dysesthesia, and xerostomia. A reduction in the dose of palbociclib did not provide relief and treatment with the inhibitor was thus discontinued, resolving the tongue symptoms. Laboratory exams were unremarkable. Given that this was a late relapse, the tumor was classified asendocrine-sensitive, a condition associated with high sensitivity to palbociclib.CONCLUSION This case highlights the potential of the cyclin-dependent kinase 4/6 inhibitor plus ET combination to achieve pCR in locoregional relapse of BC, enabling surgical resection of a lesion initially considered inoperable.

Abemaciclib, a Recent Novel FDA-Approved Small Molecule Inhibiting Cyclin-Dependant Kinase 4/6 for the Treatment of Metastatic Breast Cancer: A Mini-Review

Abemaciclib (Verzerio®) is a cell cycle inhibitor of both CDK4 and CDK6. In 2017, abemaciclib was approved by the Food and Drug Administration (FDA) and, in 2018 by the European Medicines Agency (EMA) for the treatment of postmenopausal women with hormone receptor positive (HR+), human epidermal growth factor receptor 2 negative (HER2−) advanced breast cancer. In this mini-review, we provide a series of information for respectively their targets and its selectivity, results on preclinical trial, clinical phase I, II and III trials, and some perspectives. We also describe the batch and flow steps used for the synthesis of this cancer drug.

MiR-450b-5p enhances the radiosensitivity of HR^(+) and HER2^(−) breast cancer by targeting CDK6

Background:The sensitivity of breast cancer cells to radiation is a key cause of locoregional recurrence after postoperative radiotherapy.Several studies have reported that microRNAs(miRNAs)are involved in the radiosensitivity of human breast cancer cells.One miRNA microarray study showed that miR-450b-5p was overexpressed 13.3-fold in patients with estrogen receptor–positive(ER^(+))and human epidermal growth factor receptor 2–negative(HER2−)breast cancer and no local relapse compared with local relapse patients.However,its underlying mechanism of action remains unknown.Methods:The predicted target mRNAs of miR-450b-5p were screened using the TargetScan,miRDB,and miRWalk databases.Western blotting,quantitative polymerase chain reaction,and dual-luciferase reporter assays explored the association between cyclindependent kinase 6(CDK6)and miR-450b-5p.The cell counting kit-8 assay and flow cytometry detected the proliferation of transfected MCF7 cells.Colony formation and xenograft tumors detected the radiosensitivity of the transfected MCF7 cells.Results:Bioinformatics analysis,Western blotting,quantitative polymerase chain reaction,and dual-luciferase reporter assays demonstrated that CDK6 was the target gene of miR-450b-5p.Furthermore,in vitro and in vivo experiments showed that miR-450b-5p inhibited MCF7 cell proliferation and cell cycle progression,increased the sensitizer enhancement ratio,and decreased the volume of xenograft tumors after irradiation by regulating CDK6.Conclusions:This study demonstrates that miR-450b-5p enhances the radiosensitivity of hormone receptor–positive(HR^(+))and HER2−breast cancer cells and elucidates its mechanism.miR-450b-5p may be considered a therapeutic target in HR^(+)and HER2−breast cancer treated with radiotherapy.

Promoter methylation status of hMLH1,MGMT,and CDKN2A/p16 in colorectal adenomas

AIM:To investigate aberrant DNA methylation of CpG islands and subsequent low-or high-level DNA microsatellite instability(MSI)which is assumed to drive colon carcinogenesis. METHODS:DNA of healthy individuals,adenoma(tu-bular or villous/tubulovillous)patients,and colorectal carcinoma patients who underwent colonoscopy was used for assessing the prevalence of aberrant DNA methylation of human DNA mismatch repair gene mutator L homologue 1(hMLH1),Cyclin-dependent kinase inhibitor 2A(CDKN2A/p16),and O-6-methylguanine DNA methyltransferase(MGMT),as well as their rela- tion to MSI. RESULTS:The frequency of promoter methylation for each locus increased in the sequence healthy tissue/adenoma/carcinoma.MGMT showed the highest frequency in each group.MGMT and CDKN2A/p16 presented a statistically significant increase in promoter methylation between the less and more tumorigenic forms of colorectal adenomas(tubular vs tubullovillous and villous adenomas).All patients with tubulovillous/villous adenomas,as well as all colorectal cancer patients,showed promoter methylation in at least one of the examined loci.These findings suggest a potentially crucial role for methylation in the polyp/adenoma to cancer progres- sion in colorectal carcinogenesis.MSI and methylation seem to be interdependent,as simultaneous hMLH1, CDKN2A/p16,and MGMT promoter methylation was present in 8/9 colorectal cancer patients showing the MSI phenotype. CONCLUSION:Methylation analysis of hMLH1,CD- KN2A/p16,and MGMT revealed specific methylation profiles for tubular adenomas,tubulovillous/villous adenomas,and colorectal cancers,supporting the use of these alterations in assessment of colorectal tumorigenesis.

Long non-coding RNA H19 promotes proliferation inhepatocellular carcinoma cells via H19/miR-107/CDK6 axis

Hepatocellular carcinoma (HCC) is the leading cause of cancer death worldwide;nevertheless, currenttherapeutic options are limited or ineffective for many patients. Therefore, elucidation of molecular mechanisms inHCC biology could yield important insights for the intervention of novel therapies. Recently, various studies havereported dysregulation of long non-coding RNAs (lncRNAs) in the initiation and progression of HCC, including H19;however, the biological function of H19 in HCC remains unclear. Here, we show that knockdown of H19 disruptedHCC cell growth, impaired the G1-to-S phase transition, and promoted apoptosis, while overexpression of H19yielded the opposite results. Screening for expression of cell cycle-related genes revealed a significant downregulationof CDK6 at both RNA and protein levels upon H19 suppression. Bioinformatic analysis of the H19 sequence and the3′ untranslated region (3′ UTR) of CDK6 transcripts showed several binding sites for microRNA-107 (miR-107), andthe dual luciferase reporter assay confirmed their direct interaction with miR-107. Consistently, blockage of miR-107activity alleviated the growth suppression phenotypes induced by H19 downregulation, suggesting that H19 serves asa molecular sponge for miR-107 to promote CDK6 expression and cell cycle progression. Together, this studydemonstrates a mechanistic function of H19 in driving the proliferation of HCC cells and suggests H19 suppressionas a novel approach for HCC treatment.

Insights into the Use of CDK 4/6 Inhibitors in Patients with HR-positive Advanced or Metastatic Breast Cancer

Hormone receptor(HR)-positive breast cancer(BC)is the most common subtype of BC and some patients with such tumors experience recurrences.Endocrine-based therapy(ET)(e.g.,tamoxifen,aromatase inhibitors(AIs),and fulvestrant)that has improved outcomes in such patients represents the initial therapy for women with HR-positive/human epidermal growth factor receptor 2(HER2)-negative BC(considering no evidence of visceral crisis).However,the resistance to ET can occur in almost 50%of HR-positive BCs.In order to improve outcomes of patients with HR-positive metastatic BC,new treatment strategies are required.One such therapy is the new class of medications,cyclin-dependent kinase(CDK)4/6 inhibitors,that have improved the outcomes in such patients(both endocrine-sensitive and endocrine-resistant).This article presents evidence from the main clinical trials,which led to the approval of palbociclib,ribociclib,and abemaciclib.These three CDK 4/6 inhibitors have shown a significant improvement of the progression-free survival(PFS)in patients with HR-positive/HER2-negative metastatic BC when used in combination with selected ETs.In addition,some important patient management considerations,when choosing a particular CDK 4/6 inhibitor for an individual patient are presented.Furthermore,a need to find biomarkers for CDK 4/6 inhibitor sensitivity,efficacy,and resistance,to be able to precisely select the best patientcandidates for this treatment is highlighted.

Expressions of miRNA29 target genes CCND2 and CDK6 in cervical cancer

Objective: To study the expression of miRNA29 target genes recombinant cyclin D2 (CCND2) and cyclin-dependent kinase 6 (CDK6) in cervical squamous cell carcinoma tissues and their relationship with clinicopathological factors. Methods: Levels of mRNA of CCND2 and CDK6 in cervical squamous cell carcinoma tissues, cervical intraepithelial neoplasia (CIN) tissues and normal cervical tissues were detected by reverse transcription-polymerase chain reaction (RT-PCR). Results: There was a statistical difference in the expression of CCND2 (one of miRNA29 target genes) in normal cervical tissues, CIN tissues and cervical squamous cell carcinoma tissues (H = 29.27, p = .00), but there was no statistical difference in the expression of CDK6 (one of miRNA29 target genes) in them (H = 2.76, p = .25). CCND2 was positively correlated to CDK6 in CIN tissues (r = 0.58, p < .05). Conclusions: CCND2, one of miRNA29 target genes, may be involved in the occurrence and development of cervical cancer, but CDK6 is less relevant to the occurrence and development of cervical cancer;CCND2 and CDK6 may play a synergistic role in the occurrence and development of CIN.

Discovery of 4-Thiazol-N-(pyridin-2-yl)pyrimidin-2-amine as Novel Cyclin-dependent Kinases 4 and 6 Dual Inhibitors via 3D-QSAR and Molecular Simulation

Cyclin D dependent kinases 4/6 regulate the entry of cells into S phase and are effective target for the discovery of anticancer drugs.In this article,3D-QSAR modeling including comparative molecular field analy-sis(CoMFA)and comparative molecular similarity indices analysis fields(CoMSIA)was implemented on 52 dual CDK4/6 inhibitors.As a result,we obtained a pretty good 3D-QSAR model,which is CoMFACDK4 with q2 to be 0.543 and r^(2) to be 0.967;CoMSIACDK4 with q2 being 0.518 and r^(2) being 0.937;CoMFACDK6 with q2 to be 0.624 and r^(2) to be 0.984;CoMSIACDK6 with q2 being 0.584 and r^(2) being 0.975.Molecular docking confirmed the important residues for interactions.Molecular dynamics simulation further confirmed binding affinity with key residues of protein,such as Lys22,Lys35,Val96 for CDK4 and Lys43,His100,Val101 for CDK6 at the active sites.Then these results offered new directions to explore new inhibitors of CDK4/6.Finally,we designed 10 novel compounds with promising expected activity and ADME/T properties,and provided referable synthetic routes.

Cell cycle regulation and anticancer drug discovery

Cellular growth,development,and differentiation are tightly controlled by a conserved biological mechanism:the cell cycle.This cycle is primarily regulated by cyclin-dependent kinase(CDK)-cyclin complexes,checkpoint kinases,and CDK inhibitors.Deregulation of the cell cycle is a hallmark of the transformation of normal cells into tumor cells.Given its importance in tumorigenesis,several cell cycle inhibitors have emerged as potential therapeutic drugs for the treatment of cancers-both as singleagent therapy and in combination with traditional cytotoxic or molecular targeting agents.In this review,we discuss the mechanisms underlying cell cycle regulation and present small-molecule anticancer drugs that are under development,including both pan-CDK inhibitors and CDK4/6-selective inhibitors.In addition,we provide an outline of some promising CDK inhibitors currently in preclinical and clinical trials that target cell cycle abnormalities in various cancers.

Disruption of δ-opioid receptor phosphorylation at Threonine 161 attenuates morphine tolerance in rats with CFA-induced inflammatory hypersensitivity

Objective Our previous study identified Threonine 161 （Thr-161）, located in the second intracellular loop of the 6-opioid receptor （DOR）, as the only consensus phosphorylation Cdte for cyclin-dqpendent kinase 5 （CdkS）. The aim of this study was to assess the function of DOR phosphorylation by Cdk5 in complete Freund＇s adjuvant （CFA）-induced inflammatory pain and morphine tolerance. Methods Dorsal root ganglion （DRG） neurons of rats with CFA-induced in- flammatory pain were acutely dissociated and the biotinylation method was used to explore the membrane localization of phosphorylated DOR at Thr-161 （pThr-161-DOR）, and paw withdrawal latency was measured after intrathecal delivery of drugs or Tat-peptide, using a radiant heat stimulator in rats with CFA-induced inflammatory pain. Results Both the total amount and the surface localization of pThr-161-DOR were significantly enhanced in the ipsilateral DRG following CFA injection. lntrathecal delivery of the engineered Tat fusion-interefering peptide corresponding to the second intracellular loop of DOR （Tat-DOR-2L） increased inflammatory hypersensitivity, and inhibited DOR- but not μ-opioid receptor-mediated spinal analgesia in CFA-treated rats. However, intrathecal delivery of Tat-DOR-2L postponed morphine antinociceptive tolerance in rats with CFA-induced inflammatory pain. Conclusion Phosphorylation of DOR at Thr-161 by Cdk5 attenuates hypersensitivity and potentiates morphine tolerance in rats with CFA-induced inflammatory pain, while disruption of the phosphorylation of DOR at Thr- 161 attenuates morphine tolerance.

Role of senescence induction in cancer treatment

Cellular senescence is a form of permanent cell cycle arrest that can be triggered by a variety of cell-intrinsic and extrinsic stimuli, including telomere shortening,DNA damage, oxidative stress, and exposure to chemotherapeutic agents and ionizing radiation. Although the induction of apoptotic cell death is a desirable outcome in cancer therapy, mutations and/or deficiencies in the apoptotic signaling pathways have been frequently identified in many human cancer types,suggesting the importance of alternative apoptosis-independent therapeutic approaches for cancer treatment. A growing body of evidence has documented that senescence induction in tumor cells is a frequent response to many anticancer modalities including cyclin-dependent kinases 4/6 small molecule inhibitor-based targeted therapeutics and T helper-1 cytokine-mediated immunotherapy. This review discusses the recent advances and clinical relevance of therapy-induced senescence in cancer treatment.

Gap junctions enhance the antiproliferative effect of microrna-124-3p in glioblastoma cells

OBJECTIVE MicroR NA(miR NA)holds promise as a novel therapeutic tool for cancer treatment.However,the transfection efficiency of current delivery systems represents a bottleneck for clinical applications.Here,we demonstrate that gap junctions mediate an augmentative effect on the antiproliferation mediated by mi R-124-3p in U87 and C6 glioblastoma cells.METHODS The functional inhibition of gap junctions using either si RNA or pharmacological inhibition eliminated the mi R-124-3p-mediated antiproliferation,whereas the enhancement of gap junctions with retinoic acid treatment augmented this mi R-124-3p-mediated antiproliferation.A similar effect was observed in glioblastoma xenograft models.RESULTS More importantly,patch clamp and co-culture assays demonstrated the transmission of mi R-124-3p through gap junction channels into adjacent cells.In further exploring the impact of gap junction-mediated transport of mi R-124-3p on mi R-124-3p target pathways,we found that mi R-124-3p inhibited glioblastoma cell growth in part by decreasing the protein expression of cyclindependent kinase 6,leading to cel cycle arrest at the G0/G1phase;moreover,pharmacological regulation of gap junctions affected this cell cycle arrest.CONCLUSION Our results indicate that the″bystander″effects of functional gap junctions composed of connexin 43 enhance the antitumor effect of mi R-124-3p in glioblastoma cells by transferring mi R-124-3p to adjacent cells,thereby enhancing G0/G1cell cycle arrest.These observations provide a new guiding strategy for the clinical application of mi RNA therapy in tumor treatment.

转移性激素受体阳性乳腺癌内分泌治疗耐药及治疗决策进展

内分泌治疗已成为转移性激素受体(hormone receptor,HR)阳性乳腺癌的治疗基础。内分泌耐药的发生使得很多新型内分泌治疗药物或药物组合被研发出来。细胞周期蛋白依赖性激酶(cyclin-dependent protein kinase,CDK)4/6抑制剂的应用可显著延长内分泌耐药患者的无进展生存时间。有多项关于使用磷脂酰肌醇3激酶(phosphatidylinositol 3-kinase,PI3K)抑制剂和哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin,mTOR)抑制剂作为后续治疗方案的研究,特别是针对内分泌耐药的情况,应基于合并症、既往辅助治疗、患者的生活质量、不良反应及无病间隔期的情况,选择治疗方案的最佳顺序。对转移性乳腺癌的特定生物标志物检测以及新型基因检测对预测治疗效果、耐药性以及预后均具有重要意义,有助于进一步推动精准治疗的发展。

Targeted lapatinib anti-HER2/ErbB2 therapy resistance in breast cancer:opportunities to overcome a difficult problem

Approximately 20%of invasive breast cancers have upregulation/gene amplification of the oncogene human epidermal growth factor receptor-2(HER2/ErbB2).Of these,some also express steroid receptors(the so-called Luminal B subtype),whereas others do not(the HER2 subtype).HER2 abnormal breast cancers are associated with a worse prognosis,chemotherapy resistance,and sensitivity to selected anti-HER2 targeted therapeutics.Transcriptional data from over 3000 invasive breast cancers suggest that this approach is overly simplistic;rather,the upregulation of HER2 expression resulting from gene amplification is a driver event that causes major transcriptional changes involving numerous genes and pathways in breast cancer cells.Most notably,this includes a shift from estrogenic dependence to regulatory controls driven by other nuclear receptors,particularly the androgen receptor.We discuss members of the HER receptor tyrosine kinase family,heterodimer formation,and downstream signaling,with a focus on HER2 associated pathology in breast carcinogenesis.The development and application of anti-HER2 drugs,including selected clinical trials,are discussed.In light of the many excellent reviews in the clinical literature,our emphasis is on recently developed and successful strategies to overcome targeted therapy resistance.These include combining anti-HER2 agents with programmed cell death-1 ligand or cyclin-dependent kinase 4/6 inhibitors,targeting crosstalk between HER2 and other nuclear receptors,lipid/cholesterol synthesis to inhibit receptor tyrosine kinase activation,and metformin,a broadly inhibitory drug.We seek to facilitate a better understanding of new approaches to overcome anti-HER2 drug resistance and encourage exploration of two other therapeutic interventions that may be clinically useful for HER+invasive breast cancer patients.