Targeting CDK4 and CDK6 in cancer

Promising targetable biomarkers in pancreatic neuroendocrine tumours

INTRODUCTION

In the treatment scenario of PanNETs-targeted therapies are desired but limited, as rarity and heterogeneity on PanNETs pose limitations to their development.

AREAS COVERED

We performed a literature review searching for promising druggable biomarkers and potential treatments to be implemented in the next future. We focused on treatments which have already reached clinical experimentation, although in early phases. Six targets were identified, namely Hsp90, HIFa, HDACs, CDKs, uPAR, and DDR. Even though biological rational is strong, so far reported efficacy outcomes are quite disappointing. The reason of that should be searched in the patients' heterogeneity, lack of biomarker selection, poor knowledge of interfering mechanisms as well as difficulties in patients accrual. Moreover, different ways to assess treatment efficacy should be considered, other than response rate, in light of the more indolent nature of NETs.

EXPERT OPINION

Development of targeted treatments in PanNETs is still an uncovered area, far behind other more frequent cancers. Rarity of NETs led to accrual of unselected populations, possibly jeopardizing the drug efficacy. Better patients' selection, both in terms of topography, grading and biomarkers is crucial and will help understanding which role targeted therapies can really play in these tumors.

FRMD8 targets both CDK4 activation and RB degradation to suppress colon cancer growth

Cyclin-dependent kinase 4 (CDK4) and retinoblastoma protein (RB) are both important cell-cycle regulators that function in different scenarios. Here, we report that FERM domain-containing 8 (FRMD8) inhibits CDK4 activation and stabilizes RB, thereby causing cell-cycle arrest and inhibiting colorectal cancer (CRC) cell growth. FRMD8 interacts separately with CDK7 and CDK4, and it disrupts the interaction of CDK7 with CDK4, subsequently inhibiting CDK4 activation. FRMD8 competes with MDM2 to bind RB and attenuates MDM2-mediated RB degradation. Frmd8 deficiency in mice accelerates azoxymethane/dextran-sodium-sulfate-induced colorectal adenoma formation. The FRMD8 promoter is hypermethylated, and low expression of FRMD8 predicts poor prognosis in CRC patients. Further, we identify an LKCHE-containing FRMD8 peptide that blocks MDM2 binding to RB and stabilizes RB. Combined application of the CDK4 inhibitor and FRMD8 peptide leads to marked suppression of CRC cell growth. Therefore, using an LKCHE-containing peptide to interfere with the MDM2-RB interaction may have therapeutic value in CDK4/6 inhibitor-resistant patients.

Design, synthesis, in vitro anticancer, molecular docking and SAR studies of new series of pyrrolo[2,3-d]pyrimidine derivatives

The current study involves the design and synthesis of a newly synthesized pyrrolo[2,3-d]pyrimidine derivatives to contain chlorine atoms in positions 4 and 6 and trichloromethyl group in position 2 using microwave technique as a new and robust approach for preparation of this type of pyrrolo[2,3-d]pyrimidine derivatives. The chemical structure of the synthesized pyrrolo[2,3-d]pyrimidine derivatives 3-19 was well-characterized using spectral and elemental analyses as well as single-crystal X-ray diffraction. All compounds were tested in vitro against seven selected human cancer cell lines, namely, MCF7, A549, HCT116, PC3, HePG2, PACA2 and BJ1 using MTT assay. It was found that compounds 14a, 16b and 18b were the most active toward MCF7 with IC50 (1.7, 5.7, and 3.4 μg/ml, respectively) relative to doxorubicin (Dox.) (26.1 μg/ml). Additionally, compound 17 exerted promising cytotoxic effects against HePG2 and PACA2 with IC50 (8.7 and 6.4 μg/ml, respectively) relative to Dox. (21.6 and 28.3 μg/ml, respectively). The molecular docking study confirmed our ELISA result which showed the promising binding affinities of compounds 14a and 17 against Bcl2 anti-apoptotic protein. At the gene expression level, P53, BAX, DR4 and DR5 were up-regulated, while Bcl2, Il-8, and CDK4 were down-regulated in 14a, 14b and 18b treated MCF7 cells. At the protein level, compound 14b increased the activity of Caspase 8 and BAX (18.263 and 14.25 pg/ml) relative to Dox. (3.99 and 4.92 pg/ml, respectively), while the activity of Bcl2 was greatly decreased in 14a treated MCF7 (2.4 pg/ml) compared with Dox. (14.37 pg/ml). Compounds 14a and 14b caused cell cycle arrest at the G1/S phase in MCF7. Compounds 16b and 18b induced the apoptotic death of MCF7 cells. In addition, the percentage of fragmented DNA was increased significantly in 14a treated MCF7 cells.

Targeting Breast Cancer: The Familiar, the Emerging, and the Uncharted Territories

Breast cancer became the most diagnosed cancer in the world in 2020. Chemotherapy is still the leading clinical strategy in breast cancer treatment, followed by hormone therapy (mostly used in hormone receptor-positive types). However, with our ever-expanding knowledge of signaling pathways in cancer biology, new molecular targets are identified for potential novel molecularly targeted drugs in breast cancer treatment. While this has resulted in the approval of a few molecularly targeted drugs by the FDA (including drugs targeting immune checkpoints), a wide array of signaling pathways seem to be still underexplored. Also, while combinatorial treatments have become common practice in clinics, the majority of these approaches seem to combine molecularly targeted drugs with chemotherapeutic agents. In this manuscript, we start by analyzing the list of FDA-approved molecularly targeted drugs for breast cancer to evaluate where molecular targeting stands in breast cancer treatment today. We will then provide an overview of other options currently under clinical trial or being investigated in pre-clinical studies.

Inhibition of VCP modulates NF-κB signaling pathway to suppress multiple myeloma cell proliferation and osteoclast differentiation

Multiple myeloma (MM) is the second most common hematological malignancy, in which the dysfunction of the ubiquitin-proteasome pathway is associated with the pathogenesis. The valosin containing protein (VCP)/p97, a member of the AAA+ ATPase family, possesses multiple functions to regulate the protein quality control including ubiquitin-proteasome system and molecular chaperone. VCP is involved in the occurrence and development of various tumors while still elusive in MM. VCP inhibitors have gradually shown great potential for cancer treatment. This study aims to identify if VCP is a therapeutic target in MM and confirm the effect of a novel inhibitor of VCP (VCP20) on MM. We found that VCP was elevated in MM patients and correlated with shorter survival in clinical TT2 cohort. Silencing VCP using siRNA resulted in decreased MM cell proliferation via NF-κB signaling pathway. VCP20 evidently inhibited MM cell proliferation and osteoclast differentiation. Moreover, exosomes containing VCP derived from MM cells partially alleviated the inhibitory effect of VCP20 on cell proliferation and osteoclast differentiation. Mechanism study revealed that VCP20 inactivated the NF-κB signaling pathway by inhibiting ubiquitination degradation of IκBα. Furthermore, VCP20 suppressed MM cell proliferation, prolonged the survival of MM model mice and improved bone destruction in vivo. Collectively, our findings suggest that VCP is a novel target in MM progression. Targeting VCP with VCP20 suppresses malignancy progression of MM via inhibition of NF-κB signaling pathway.

Co-targeting RANK pathway treats and prevents acquired resistance to CDK4/6 inhibitors in luminal breast cancer

The combination of endocrine therapy (ET) and cyclin-dependent kinase 4/6 (CDK4/6) inhibitors (CDK4/6i) was a hallmark in metastatic luminal breast cancer (BC). However, intrinsic and acquired resistance affects long-term efficacy. Here, we study the role of the receptor activator of nuclear factor-κB (RANK) pathway in CDK4/6i resistance. We find that RANK overexpression in luminal BC is associated with intrinsic resistance to CDK4/6i, both in vitro and in mouse xenografts, and decreased proliferation rate and chronic interferon (IFN) γ response are highlighted as resistance drivers. Gene expression data from the NeoPalAna CDK4/6i clinical trial, and studies with palbociclib-resistant cell lines, show that RANK is upregulated after treatment with CDK4/6i, supporting a role in acquired resistance. Our study shows that RANK ligand (RANKL) inhibitors can restore sensitivity to CDK4/6i and prevent acquired resistance. On the basis of these findings, we conclude that pharmacological inhibition of the RANK pathway through RANKL blocking could represent an add-on to ET + CDK4/6i, warranting further clinical studies.

Transcriptomic analyses of ovarian clear-cell carcinoma with concurrent endometriosis

Introduction

Endometriosis, a benign inflammatory disease whereby endometrial-like tissue grows outside the uterus, is a risk factor for endometriosis-associated ovarian cancers. In particular, ovarian endometriomas, cystic lesions of deeply invasive endometriosis, are considered the precursor lesion for ovarian clear-cell carcinoma (OCCC).

Methods

To explore this transcriptomic landscape, OCCC from women with pathology-proven concurrent endometriosis (n = 4) were compared to benign endometriomas (n = 4) by bulk RNA and small-RNA sequencing.

Results

Analysis of protein-coding genes identified 2449 upregulated and 3131 downregulated protein-coding genes (DESeq2, P< 0.05, log2 fold-change > |1|) in OCCC with concurrent endometriosis compared to endometriomas. Gene set enrichment analysis showed upregulation of pathways involved in cell cycle regulation and DNA replication and downregulation of pathways involved in cytokine receptor signaling and matrisome. Comparison of pathway activation scores between the clinical samples and publicly-available datasets for OCCC cell lines revealed significant molecular similarities between OCCC with concurrent endometriosis and OVTOKO, OVISE, RMG1, OVMANA, TOV21G, IGROV1, and JHOC5 cell lines. Analysis of miRNAs revealed 64 upregulated and 61 downregulated mature miRNA molecules (DESeq2, P< 0.05, log2 fold-change > |1|). MiR-10a-5p represented over 21% of the miRNA molecules in OCCC with endometriosis and was significantly upregulated (NGS: log2fold change = 4.37, P = 2.43e-18; QPCR: 8.1-fold change, P< 0.05). Correlation between miR-10a expression level in OCCC cell lines and IC50 (50% inhibitory concentration) of carboplatin in vitro revealed a positive correlation (R2 = 0.93). MiR-10a overexpression in vitro resulted in a significant decrease in proliferation (n = 6; P< 0.05) compared to transfection with a non-targeting control miRNA. Similarly, the cell-cycle analysis revealed a significant shift in cells from S and G2 to G1 (n = 6; P< 0.0001). Bioinformatic analysis predicted that miR-10a-5p target genes that were downregulated in OCCC with endometriosis were involved in receptor signaling pathways, proliferation, and cell cycle progression. MiR-10a overexpression in vitro was correlated with decreased expression of predicted miR-10a target genes critical for proliferation, cell-cycle regulation, and cell survival including [SERPINE1 (3-fold downregulated; P< 0.05), CDK6 (2.4-fold downregulated; P< 0.05), and RAP2A (2-3-fold downregulated; P< 0.05)].

Discussion

These studies in OCCC suggest that miR-10a-5p is an impactful, potentially oncogenic molecule, which warrants further studies.

Histone acetylation by HBO1 (KAT7) activates Wnt/β-catenin signaling to promote leukemogenesis in B-cell acute lymphoblastic leukemia

B-cell acute lymphoblastic leukemia (B-ALL) is an aggressive hematological disorder with a dismal prognosis. The dysregulation of histone acetylation is of great significance in the pathogenesis and progression of B-ALL. Regarded as a fundamental acetyltransferase gene, the role of HBO1 (lysine acetyltransferase 7/KAT7) in B-ALL has not been investigated. Herein, we found that HBO1 expression was elevated in human B-ALL cells and associated with poor disease-free survival. Strikingly, HBO1 knockdown inhibited viability, proliferation, and G1-S cycle progression in B-ALL cells, while provoking apoptosis. In contrast, ectopic overexpression of HBO1 enhanced cell viability and proliferation but inhibited apoptotic activation. The results of in vivo experiments also certificated the inhibitory effect of HBO1 knockdown on tumor growth. Mechanistically, HBO1 acetylated histone H3K14, H4K8, and H4K12, followed by upregulating CTNNB1 expression, resulting in activation of the Wnt/β-catenin signaling pathway. Moreover, a novel small molecule inhibitor of HBO1, WM-3835, potently inhibited the progression of B-ALL. Our data identified HBO1 as an efficacious regulator of CTNNB1 with therapeutic potential in B-ALL.

Cancer invasion and metastasis: Insights from murine pubertal mammary gland morphogenesis

Cancer invasion and metastasis accounts for the majority of cancer related mortality. A better understanding of the players that drive the aberrant invasion and migration of tumors cells will provide critical targets to inhibit metastasis. Postnatal pubertal mammary gland morphogenesis is characterized by highly proliferative, invasive, and migratory normal epithelial cells. Identifying the molecular regulators of pubertal gland development is a promising strategy since tumorigenesis and metastasis is postulated to be a consequence of aberrant reactivation of developmental stages. In this review, we summarize the pubertal morphogenesis regulators that are involved in cancer metastasis and revisit pubertal mammary gland transcriptome profiling to uncover both known and unknown metastasis genes. Our updated list of pubertal morphogenesis regulators shows that most are implicated in invasion and metastasis. This review highlights molecular linkages between development and metastasis and provides a guide for exploring novel metastatic drivers.

Emerging Therapies for Breast Cancer

The steady, incremental improvements in outcomes for both early-stage and advanced breast cancer patients are, in large part, attributable to the success of novel systemic therapies. In this review, we discuss key conceptual paradigms that have underpinned this success including (1) targeting the driver: the identification and targeting of major oncoproteins in breast cancers; (2) targeting the lineage pathway: inhibition of those pathways that drive normal mammary epithelial cell proliferation that retain importance in cancer; (3) targeting precisely: the application of molecular classifiers to refine therapy selection for specific cancers, and of antibody-drug conjugates to pinpoint tumor and tumor promoting cells for eradication; and (4) exploiting synthetic lethality: leveraging unique vulnerabilities that cancer-specific molecular alterations induce. We describe promising examples of novel therapies that have been discovered within each of these paradigms and suggest how future drug development efforts might benefit from the continued application of these principles.

Biological function and research progress of N6-methyladenosine binding protein heterogeneous nuclear ribonucleoprotein A2B1 in human cancers

N6-methyladenosine (m6A) is the most prevalent internal modification found in both mRNA and lncRNA. It exerts reversible regulation over RNA function and affects RNA processing and metabolism in various diseases, especially tumors. The m6A binding protein, hnRNPA2B1, is extensively studied as a member of the heterogeneous nuclear ribonucleoprotein (hnRNP) protein family. It is frequently dysregulated and holds significant importance in multiple types of tumors. By recognizing m6A sites for variable splicing, maintaining RNA stability, and regulating translation and transport, hnRNPA2B1 plays a vital role in various aspects of tumor development, metabolism, and regulation of the immune microenvironment. In this review, we summarized the latest research on the functional roles and underlying molecular mechanisms of hnRNPA2B1. Moreover, we discussed its potential as a target for tumor therapy.

Cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors: existing and emerging differences

The cyclin-dependent kinase 4 and 6 (CDK4/6) inhibitors palbociclib, ribociclib, and abemaciclib are standard-of-care therapy for hormone receptor-positive advanced or metastatic breast cancer, based on randomized trials showing improved progression-free survival for all 3 drugs and overall survival for ribociclib and abemaciclib. Results in early breast cancer are discordant, with sustained improvement in invasive disease-free survival demonstrated for abemaciclib but not other CDK4/6 inhibitors to date. We review nonclinical studies exploring mechanistic differences between the drugs, the impact of continuous dosing on treatment effect, and translational research into potential resistance mechanisms and prognostic and predictive markers. We focus particularly on how emerging findings may help us understand similarities and differences between the available CDK4/6 inhibitors. Even at late-stage clinical development, there remains much to learn about how agents in this class exert their varying effects.

Immunomodulatory effects of CDK4/6 inhibitors

The dysregulation of the cell cycle is one of the hallmarks of cancer. Cyclin-dependent kinase 4 (CDK4) and CDK6 play crucial roles in regulating cell cycle and other cellular functions. CDK4/6 inhibitors have achieved great success in treating breast cancers and are currently being tested extensively in other tumor types as well. Accumulating evidence suggests that CDK4/6 inhibitors exert antitumor effects through immunomodulation aside from cell cycle arrest. Here we outline the immunomodulatory activities of CDK4/6 inhibitors, discuss the immune mechanisms of drug resistance and explore avenues to harness their immunotherapeutic potential when combined with immune checkpoint inhibitors (ICIs) or chimeric antigen receptor (CAR) T-cell therapy to improve the clinical outcomes.

Autophagy Inhibition Contributes to Apoptosis of PLK4 Downregulation-induced Dormant Cells in Colorectal Cancer

Dormant cancer cells account for cancer recurrence, distant metastasis and drug resistance which lead to poor prognosis in colorectal cancer (CRC). However, little is known about the molecular mechanisms regulating tumor cell dormancy and how to eliminate dormant cancer cells. Recent studies indicate autophagy affects dormant tumor cell survival. Here, we found that polo-like kinases 4 (PLK4), a central regulator of the cell cycle and proliferation, plays a crucial role in regulating CRC cells dormancy both in vitro and in vivo. Downregulation of PLK4 induced dormancy and inhibited migration and invasion in different CRC cell lines. Clinically, PLK4 expression was correlated with the dormancy markers (Ki67, p-ERK, p-p38) and late recurrence in CRC tissues. Mechanistically, downregulation of PLK4 induced autophagy contributed to restoring phenotypically aggressive tumor cells to a dormant state through the MAPK signaling pathway, and inhibition of autophagy would trigger apoptosis of dormant cells. Our findings reveal that downregulation of PLK4-induced autophagy contributes to tumor dormancy and autophagy inhibition leads to apoptosis of CRC dormant cells. Our study is the first to report that downregulation PLK4 induced autophagy is an early event in CRC dormancy and highlights autophagy inhibitor as a potential therapeutic target for dormant cell elimination.

The mechanism and clinical application of DNA damage repair inhibitors combined with immune checkpoint inhibitors in the treatment of urologic cancer

Urologic cancers such as kidney, bladder, prostate, and uroepithelial cancers have recently become a considerable global health burden, and the response to immunotherapy is limited due to immune escape and immune resistance. Therefore, it is crucial to find appropriate and effective combination therapies to improve the sensitivity of patients to immunotherapy. DNA damage repair inhibitors can enhance the immunogenicity of tumor cells by increasing tumor mutational burden and neoantigen expression, activating immune-related signaling pathways, regulating PD-L1 expression, and reversing the immunosuppressive tumor microenvironment to activate the immune system and enhance the efficacy of immunotherapy. Based on promising experimental results from preclinical studies, many clinical trials combining DNA damage repair inhibitors (e.g., PARP inhibitors and ATR inhibitors) with immune checkpoint inhibitors (e.g., PD-1/PD-L1 inhibitors) are underway in patients with urologic cancers. Results from several clinical trials have shown that the combination of DNA damage repair inhibitors with immune checkpoint inhibitors can improve objective rates, progression-free survival, and overall survival (OS) in patients with urologic tumors, especially in patients with defective DNA damage repair genes or a high mutational load. In this review, we present the results of preclinical and clinical trials of different DNA damage repair inhibitors in combination with immune checkpoint inhibitors in urologic cancers and summarize the potential mechanism of action of the combination therapy. Finally, we also discuss the challenges of dose toxicity, biomarker selection, drug tolerance, drug interactions in the treatment of urologic tumors with this combination therapy and look into the future direction of this combination therapy.

Functional inference of long non-coding RNAs through exploration of highly conserved regions

Background: Long non-coding RNAs (lncRNAs), which are generally less functionally characterized or less annotated, evolve more rapidly than mRNAs and substantially possess fewer sequence conservation patterns than protein-coding genes across divergent species. People assume that the functional inference could be conducted on the evolutionarily conserved long non-coding RNAs as they are most likely to be functional. In the past decades, substantial progress has been made in discussions on the evolutionary conservation of non-coding genomic regions from multiple perspectives. However, understanding their conservation and the functions associated with sequence conservation in relation to further corresponding phenotypic variability or disorders still remains incomplete. Results: Accordingly, we determined a highly conserved region (HCR) to verify the sequence conservation among long non-coding RNAs and systematically profiled homologous long non-coding RNA clusters in humans and mice based on the detection of highly conserved regions. Moreover, according to homolog clustering, we explored the potential function inference via highly conserved regions on representative long non-coding RNAs. On lncRNA XACT, we investigated the potential functional competence between XACT and lncRNA XIST by recruiting miRNA-29a, regulating the downstream target genes. In addition, on lncRNA LINC00461, we examined the interaction relationship between LINC00461 and SND1. This interaction or association may be perturbed during the progression of glioma. In addition, we have constructed a website with user-friendly web interfaces for searching, analyzing, and downloading to present the homologous clusters of humans and mice. Conclusion: Collectively, homolog clustering via the highly conserved region definition and detection on long non-coding RNAs, as well as the functional explorations on representative sequences in our research, would provide new evidence for the potential function of long non-coding RNAs. Our results on the remarkable roles of long non-coding RNAs would presumably provide a new theoretical basis and candidate diagnostic indicators for tumors.

Ethyl acetate extract of Antenoron Filiforme inhibits the proliferation of triple negative breast cancer cells via suppressing Skp2/p21 signaling axis

BACKGROUND

Triple negative breast cancer (TNBC) has the worst prognosis of the any breast cancer subtype, and the efficient therapeutical treatment is extremely limited. Antenoron filiforme (Thunb.) Roberty & Vautier (AF) is a Traditional Chinese Medicine (TCM), which is well-known for a diverse array of pharmacological activities, including but not limited to anti-inflammatory, antioxidant and anti-tumors properties. Clinically, AF is commonly prescribed for the treatment of gynecological diseases.

PURPOSE

Since TNBC is one of the worst gynecological diseases, the objective of this research is to study the anti-TNBC function of the ethyl acetate extract (EAE) of AF (AF-EAE) and disclose its mechanism of action.

MATERIALS AND METHODS

With the aim of elucidating the underlying molecular mechanism and possible chemical basis of AF-EAE in the treatment of TNBC, a comprehensive approach combining system pharmacology and transcriptomic analysis, functional experimental validation, and computational modeling was implemented. Firstly, the potential therapeutic targets of AF-EAE treating TNBC were analyzed by systemic pharmacology and transcriptome sequencing. Subsequently, cell viability assays, cell cycle assays, and transplantation tumor assays were employed to detect the inhibitory effect of AF-EAE on TNBC. Apart from that, the western blot and RT-qPCR assays were adopted to verify its mechanism of action. Finally, the potential chemical basis of anti-TNBC function of AF-EAE was screened through molecular docking and validated by molecular dynamics.

RESULTS

This study analyzed the differentially expressed genes after AF-EAE treatment by RNA-sequencing (RNA-seq). It was found that most of the genes were abundant in the gene set termed "cell cycle". Besides, AF-EAE could suppress the proliferation of TNBC cells in vitro and in vivo by inhibiting the function of Skp2 protein. AF-EAE could also lead to the accumulation of p21 and a decrease of CDK6/CCND1 protein, thereby stalling the cycle of cell in the G1/S stage. Notably, clinical data survival analysis clearly demonstrated that Skp2 overexpression has been negatively correlated with survival rates in breast cancer (BC) patients. Further, as suggested by molecular docking and molecular dynamics, the quercetin and its analogues of AF-EAE might bind to Skp2 protein.

CONCLUSION

In summary, AF-EAE inhibits the growth of TNBC in vitro and in vivo through targeting Skp2/p21 signaling pathway. While providing a novel potential drug for treating TNBC, this study might establish a method to delve into the action mechanism of TCM.

Mutational landscape of primary spinal cord astrocytoma

Primary spinal cord astrocytoma (SCA) is a rare disease. Knowledge about the molecular profiles of SCAs mostly comes from intracranial glioma; the pattern of genetic alterations of SCAs is not well understood. Herein, we describe genome-sequencing analyses of primary SCAs, aiming to characterize the mutational landscape of primary SCAs. We utilized whole exome sequencing (WES) to analyze somatic nucleotide variants (SNVs) and copy number variants (CNVs) among 51 primary SCAs. Driver genes were searched using four algorithms. GISTIC2 was used to detect significant CNVs. Additionally, recurrently mutated pathways were also summarized. A total of 12 driver genes were identified. Of those, H3F3A (47.1%), TP53 (29.4%), NF1 (19.6%), ATRX (17.6%), and PPM1D (17.6%) were the most frequently mutated genes. Furthermore, three novel driver genes seldom reported in glioma were identified: HNRNPC, SYNE1, and RBM10. Several germline mutations, including three variants (SLC16A8 rs2235573, LMF1 rs3751667, FAM20C rs774848096) that were associated with risk of brain glioma, were frequently observed in SCAs. Moreover, 12q14.1 (13.7%) encompassing the oncogene CDK4 was recurrently amplified and negatively affected patient prognosis. Besides frequently mutated RTK/RAS pathway and PI3K pathway, the cell cycle pathway controlling the phosphorylation of retinoblastoma protein (RB) was mutated in 39.2% of patients. Overall, a considerable degree of the somatic mutation landscape is shared between SCAs and brainstem glioma. Our work provides a key insight into the molecular profiling of primary SCAs, which might represent candidate drug targets and complement the molecular atlas of glioma. © 2023 The Pathological Society of Great Britain and Ireland.

A multi-functional nano-system combining PI3K-110α/β inhibitor overcomes P-glycoprotein mediated MDR and improves anti-cancer efficiency

P-glycoprotein (P-gp/ABCB1)-mediated multidrug resistance (MDR) in cancers severely limit chemotherapeutic efficacy. We recently reported that phosphatidylinositol-3-kinase (PI3K) 110α and 110β subunits can be novel targets for reversal of P-gp mediated MDR in cancers, and BAY-1082439 as an inhibitor specific for PI3K 110α and 110β subunits could reverse P-gp-mediated MDR by downregulating P-gp expression in cancer cells. However, BAY-1082439 has very low solubility, short half-life and high in-vivo clearance rate. Till now, nano-system with the functions to target PI3K P110α and P110β and reverse P-gp mediated MDR in cancers has not been reported. In our study, a tumor targeting drug delivery nano-system PBDF was established, which comprised doxorubicin (DOX) and BAY-1082439 respectively encapsulated by biodegradable PLGA-SH nanoparticles (NPs) that were grafted to gold nanorods (Au NRs) modified with FA-PEG-SH, to enhance the efficacy to reverse P-gp mediated MDR and to target tumor cells, further, to enhance the efficiency to inhibit MDR tumors overexpressing P-gp. In-vitro experiments indicated that PBDF NPs greatly enhanced uptake of DOX, improved the activity to reverse MDR, inhibited the cell proliferation, and induced S-phase arrest and apoptosis in KB-C2 cells, as compared with free DOX combining free BAY-1082439. In-vivo experiments further demonstrated that PBDF NPs improved the anti-tumor ability of DOX and inhibited development of KB-C2 tumors. Notably, the metastasis of KB-C2 cells in livers and lungs of nude mice were inhibited by treatment with PBDF NPs, which showed no obvious in-vitro or in-vivo toxicity.

Mechanisms of chromosomal instability (CIN) tolerance in aggressive tumors: surviving the genomic chaos

Chromosomal instability (CIN) is a pervasive feature of human cancers involved in tumor initiation and progression and which is found elevated in metastatic stages. CIN can provide survival and adaptation advantages to human cancers. However, too much of a good thing may come at a high cost for tumor cells as excessive degree of CIN-induced chromosomal aberrations can be detrimental for cancer cell survival and proliferation. Thus, aggressive tumors adapt to cope with ongoing CIN and most likely develop unique susceptibilities that can be their Achilles' heel. Determining the differences between the tumor-promoting and tumor-suppressing effects of CIN at the molecular level has become one of the most exciting and challenging aspects in cancer biology. In this review, we summarized the state of knowledge regarding the mechanisms reported to contribute to the adaptation and perpetuation of aggressive tumor cells carrying CIN. The use of genomics, molecular biology, and imaging techniques is significantly enhancing the understanding of the intricate mechanisms involved in the generation of and adaptation to CIN in experimental models and patients, which were not possible to observe decades ago. The current and future research opportunities provided by these advanced techniques will facilitate the repositioning of CIN exploitation as a feasible therapeutic opportunity and valuable biomarker for several types of human cancers.

MUC1-C is necessary for SHP2 activation and BRAF inhibitor resistance in BRAF(V600E) mutant colorectal cancer

Colorectal cancers (CRCs) harboring the BRAF(V600E) mutation are associated with aggressive disease and resistance to BRAF inhibitors by feedback activation of the receptor tyrosine kinase (RTK)→RAS→MAPK pathway. The oncogenic MUC1-C protein promotes progression of colitis to CRC; whereas there is no known involvement of MUC1-C in BRAF(V600E) CRCs. The present work demonstrates that MUC1 expression is significantly upregulated in BRAF(V600E) vs wild-type CRCs. We show that BRAF(V600E) CRC cells are dependent on MUC1-C for proliferation and BRAF inhibitor (BRAFi) resistance. Mechanistically, MUC1-C integrates induction of MYC in driving cell cycle progression with activation of the SHP2 phosphotyrosine phosphatase, which enhances RTK-mediated RAS→ERK signaling. We demonstrate that targeting MUC1-C genetically and pharmacologically suppresses (i) activation of MYC, (ii) induction of the NOTCH1 stemness factor, and (iii) the capacity for self-renewal. We also show that MUC1-C associates with SHP2 and is required for SHP2 activation in driving BRAFi-induced feedback of ERK signaling. In this way, targeting MUC1-C in BRAFi-resistant BRAF(V600E) CRC tumors inhibits growth and sensitizes to BRAF inhibition. These findings demonstrate that MUC1-C is a target for the treatment of BRAF(V600E) CRCs and for reversing their resistance to BRAF inhibitors by suppressing the feedback MAPK pathway.

Influence of cyclin D1 splicing variants expression on breast cancer chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway

Cyclin D1 (CCND1), a mediator of cell cycle control, has a G870A polymorphism which results in the formation of two splicing variants: full-length CCND1 (CCND1a) and C-terminally truncated CCND1 species (CCND1b). However, the role of CCND1a and CCND1b variants in cancer chemoresistance remains unknown. Therefore, this study aimed to explore the molecular mechanism of alternative splicing of CCND1 in breast cancer (BC) chemoresistance. To address the contribution of G870A polymorphism to the production of CCND1 variants in BC chemoresistance, we sequenced the G870A polymorphism and analysed the expressions of CCND1a and CCND1b in MCF-7 and MCF-7/ADM cells. In comparison with MCF-7 cells, MCF-7/ADM cells with the A allele could enhance alternative splicing with the increase of SC-35, upregulate the ratio of CCND1b/a at both mRNA and protein levels, and activate the CDK4/CyclinD1-pRB-E2F1 pathway. Furthermore, CCND1b expression and the downstream signalling pathway were analysed through Western blotting and cell cycle in MCF-7/ADM cells with knockdown of CCND1b. Knockdown of CCND1b downregulated the ratio of CCND1b/a, demoted cell proliferation, decelerated cell cycle progression, inhibited the CDK4/CyclinD1-pRB-E2F1 pathway and thereby decreased the chemoresistance of MCF-7/ADM cells. Finally, CCND1 G870A polymorphism, the alternative splicing of CCDN1 was detected through Sequenom Mass ARRAY platform, Sanger sequencing, semi-quantitative RT-PCR, Western blotting and immunohistochemistry in clinical BC specimens. The increase of the ratio of CCND1b/a caused by G870A polymorphism was involved in BC chemoresistance. Thus, these findings revealed that CCND1b/a ratio caused by the polymorphism is involved in BC chemoresistance via CDK4/CyclinD1-pRB-E2F1 pathway.

A specific anti-cyclin D1 intrabody represses breast cancer cell proliferation by interrupting the cyclin D1-CDK4 interaction

BACKGROUND

Cyclin D1 overexpression may contribute to development of various cancers, including breast cancer, and thus may serve as a key cancer diagnostic marker and therapeutic target. In our previous study, we generated a cyclin D1-specific single-chain variable fragment antibody (ADκ) from a human semi-synthetic single-chain variable fragment library. ADκ specifically interacted with recombinant and endogenous cyclin D1 proteins through an unknown molecular basis to inhibit HepG2 cell growth and proliferation.

RESULTS

Here, using phage display and in silico protein structure modeling methods combined with cyclin D1 mutational analysis, key residues that bind to ADκ were identified. Notably, residue K112 within the cyclin box was required for cyclin D1-ADκ binding. In order to elucidate the molecular mechanism underlying ADκ anti-tumor effects, a cyclin D1-specific nuclear localization signal-containing intrabody (NLS-ADκ) was constructed. When expressed within cells, NLS-ADκ interacted specifically with cyclin D1 to significantly inhibit cell proliferation, induce G1-phase arrest, and trigger apoptosis of MCF-7 and MDA-MB-231 breast cancer cells. Moreover, the NLS-ADκ-cyclin D1 interaction blocked binding of cyclin D1 to CDK4 and inhibited RB protein phosphorylation, resulting in altered expression of downstream cell proliferation-related target genes.

CONCLUSION

We identified amino acid residues in cyclin D1 that may play key roles in the ADκ-cyclin D1 interaction. A nuclear localization antibody against cyclin D1 (NLS-ADκ) was constructed and successfully expressed in breast cancer cells. NLS-ADκ exerted tumor suppressor effects via blocking the binding of CDK4 to cyclin D1 and inhibiting phosphorylation of RB. The results presented here demonstrate anti-tumor potential of intrabody-based cyclin D1-targeted breast cancer therapy.

Vacuolar protein sorting 35 (VPS35) acts as a tumor promoter via facilitating cell cycle progression in pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is insidious and highly malignant with extremely poor prognosis and drug resistance to current chemotherapies. Therefore, there is a critical need to investigate the molecular mechanism underlying PDAC progression to develop promising diagnostic and therapeutic interventions. In parallel, vacuolar protein sorting (VPS) proteins, involved in the sorting, transportation, and localization of membrane proteins, have gradually attracted the attention of researchers in the development of cancers. Although VPS35 has been reported to promote carcinoma progression, the specific molecular mechanism is still unclear. Here, we determined the impact of VPS35 on the tumorigenesis of PDAC and explored the underlying molecular mechanism. We performed a pan-cancer analysis of 46 VPS genes using RNAseq data from GTEx (control) and TCGA (tumor) and predicted potential functions of VPS35 in PDAC by enrichment analysis. Furthermore, cell cloning experiments, gene knockout, cell cycle analysis, immunohistochemistry, and other molecular and biochemical experiments were used to validate the function of VPS35. Consequently, VPS35 was found overexpressed in multiple cancers and correlated with the poor prognosis of PDAC. Meanwhile, we verified that VPS35 could modulate the cell cycle and promote tumor cell growth in PDAC. Collectively, we provide solid evidence that VPS35 facilitates the cell cycle progression as a critical novel target in PDAC clinical therapy.

Deciphering breast cancer: from biology to the clinic

Breast cancer remains a leading cause of cancer-related mortality in women, reflecting profound disease heterogeneity, metastasis, and therapeutic resistance. Over the last decade, genomic and transcriptomic data have been integrated on an unprecedented scale and revealed distinct cancer subtypes, critical molecular drivers, clonal evolutionary trajectories, and prognostic signatures. Furthermore, multi-dimensional integration of high-resolution single-cell and spatial technologies has highlighted the importance of the entire breast cancer ecosystem and the presence of distinct cellular "neighborhoods." Clinically, a plethora of new targeted therapies has emerged, now being rapidly incorporated into routine care. Resistance to therapy, however, remains a crucial challenge for the field.

PFKFB3 mediates tubular cell death in cisplatin nephrotoxicity by activating CDK4

Nephrotoxicity is a major side effect of cisplatin, a widely used cancer therapy drug. However, the mechanism of cisplatin nephrotoxicity remains unclear and no effective kidney protective strategies are available. Here, we report the induction of 6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) in both in vitro cell culture and in vivo mouse models of cisplatin nephrotoxicity. Notably, PFKFB3 was mainly induced in the nucleus of kidney tubular cells, suggesting a novel function other than its canonical role in glycolysis. Both pharmacological inhibition and genetic silencing of PFKFB3 led to the suppression of cisplatin-induced apoptosis in cultured renal proximal tubular cells (RPTCs). Moreover, cisplatin-induced kidney injury or nephrotoxicity was ameliorated in renal proximal tubule-specific PFKFB3 knockout mice. Mechanistically, we demonstrated the interaction of PFKFB3 with cyclin-dependent kinase 4 (CDK4) during cisplatin treatment, resulting in CDK4 activation and consequent phosphorylation and inactivation of retinoblastoma tumor suppressor (Rb). Inhibition of CDK4 reduced cisplatin-induced apoptosis in RPTCs and kidney injury in mice. Collectively, this study unveils a novel pathological role of PFKFB3 in cisplatin nephrotoxicity through the activation of the CDK4/Rb pathway, suggesting a new kidney protective strategy for cancer patients by blocking PFKFB3.

Relative biological effectiveness of low-energy X-rays (25 kV) in mutant p53 cancer cells

Low-energy X-rays as used in radiation therapy and diagnostics such as mammography are associated with a certain risk of promoting tumour development, especially in patients with mutations in cancer-related genes like TP53. The present study therefore addressed the relative biological effectiveness (RBE) of low-energy X-rays for two human adenocarcinoma cell lines of the breast (MDA-MB-468) and pancreas (BxPC-3) with a mutation in the TP53 gene. Clonogenic survival and cytogenetic changes in terms of micronuclei (MN) formation were determined following irradiation with 25 kV X-rays and 200 kV reference irradiation in the dose range of 1-8 Gy. Except the frequency of MN-containing binucleated cells (BNC) (BNC + MN/BNC) in breast cancer cells yielding an RBE between 0.6 and 0.8, both cell lines displayed dose-dependent variations of RBE values between 1 and 2 for all biological end points (cell survival, (BNC + MN/BNC), MN/BNC, MN/(BNC + MN)) with increased effectiveness of 25 kV irradiation in pancreatic compared to breast cancer cells. The results confirm previous findings indicating increased effectiveness of low-energy X-rays and underline the necessity of careful risk estimation for cancer screening programmes.

Maackiain inhibits proliferation and promotes apoptosis of nasopharyngeal carcinoma cells by inhibiting the MAPK/Ras signaling pathway

Nasopharyngeal carcinoma (NPC) is the third most common malignancy with a high recurrence and metastasis rate in South China. Natural compounds extracted from traditional Chinese herbal medicines have been developed and utilized for the treatment of a variety of cancers with modest properties and slight side effects. Maackiain (MA) is a type of flavonoid that was first isolated from leguminous plants, and it has been reported to relieve various nervous system disorders and exert anti-allergic as well as anti-inflammatory effects. In this study, we demonstrated that MA inhibited proliferation, arrested cell cycle and induced apoptosis in nasopharyngeal carcinoma CNE1 and CNE2 cells in vitro and in vivo. The expression of the related proteins associated with these processes were consistent with the above effects. Moreover, transcriptome sequencing and subsequent Western blot experiments revealed that inhibition of the MAPK/Ras pathway may be responsible to the anti-tumor effect of MA on NPC cells. Therefore, the effects of MA and an activator of this pathway, tertiary butylhydroquinone (TBHQ), alone or combination, were investigated. The results showed TBHQ neutralized the inhibitory effects of MA. These data suggest that MA exerts its anti-tumor effect by inhibiting the MAPK/Ras signaling pathway and it has the potential to become a treatment for patients with NPC.

Carboxypeptidase vitellogenic like facilitates resistance to CDK4/6 inhibitors in breast cancer

OBJECTIVE

Inhibitors of cyclin-dependent kinase 4 and 6 (CDK4/6) are targeted therapeutic drugs for breast cancer treatment. The mechanism of resistance to these inhibitors requires further investigation.

METHODS

We used bioinformatics to screen differentially expressed genes between cells that were susceptible and resistant to CDK4/6 inhibitors. Quantitative real-time PCR (qRT-PCR) was used to identify gene expressions in different cell lines. Cell viability, colony formation, cell cycle, and apoptosis assays were used to evaluate the effect of carboxypeptidase vitellogenic like (CPVL) on breast cancer cells under the condition of CDK4/6 inhibitors. Gene set enrichment analysis (GSEA) suggested the potential regulatory pathway of CPVL in breast cancer. Xenograft formation assay was conducted in nude mice to study the role of CPVL in vivo.

RESULTS

Based on bioinformatics analysis and qRT-PCR, CPVL was identified more abundantly in cells that were resistant than sensitive to CDK4/6 inhibitors. Overexpressed or knocked down CPVL regulated the effects of CDK4/6 inhibitors in resistant cell lines. GSEA showed that resistance might be induced by CPVL through altered phosphatase and tensin homolog (PTEN)-related pathways. Our findings showed that CPVL negatively regulates PTEN to impact the anticancer effects of CDK4/6 inhibitors in vitro and in vivo.

CONCLUSION

CPVL might be a key factor in regulating breast cancer resistance to CDK4/6 inhibitors.

AKT/mTOR signaling modulates resistance to endocrine therapy and CDK4/6 inhibition in metastatic breast cancers

Endocrine therapy (ET) in combination with CDK4/6 inhibition is routinely used as first-line treatment for HR+/HER2- metastatic breast cancer (MBC) patients. However, 30-40% of patients quickly develop disease progression. In this open-label multicenter clinical trial, we utilized a hypothesis-driven protein/phosphoprotein-based approach to identify predictive markers of response to ET plus CDK4/6 inhibition in pre-treatment tissue biopsies. Pathway-centered signaling profiles were generated from microdissected tumor epithelia and surrounding stroma/immune cells using the reverse phase protein microarray. Phosphorylation levels of the CDK4/6 downstream substrates Rb (S780) and FoxM1 (T600) were higher in patients with progressive disease (PD) compared to responders (p = 0.02). Systemic PI3K/AKT/mTOR activation in tumor epithelia and stroma/immune cells was detected in patients with PD. This activation was not explained by underpinning genomic alterations alone. As the number of FDA-approved targeted compounds increases, functional protein-based signaling analyses may become a critical component of response prediction and treatment selection for MBC patients.

Cellular senescence in the response of HR+ breast cancer to radiotherapy and CDK4/6 inhibitors

BACKGROUND

Preclinical evidence from us and others demonstrates that the anticancer effects of cyclin-dependent kinase 4/6 (CDK4/6) inhibitors can be enhanced with focal radiation therapy (RT), but only when RT is delivered prior to (rather than after) CDK4/6 inhibition. Depending on tumor model, cellular senescence (an irreversible proliferative arrest that is associated with the secretion of numerous bioactive factors) has been attributed beneficial or detrimental effects on response to treatment. As both RT and CDK4/6 inhibitors elicit cellular senescence, we hypothesized that a differential accumulation of senescent cells in the tumor microenvironment could explain such an observation, i.e., the inferiority of CDK4/6 inhibition with palbociclib (P) followed by RT (P→RT) as compared to RT followed by palbociclib (RT→P).

METHODS

The impact of cellular senescence on the interaction between RT and P was assessed by harnessing female INK-ATTAC mice, which express a dimerizable form of caspase 8 (CASP8) under the promoter of cyclin dependent kinase inhibitor 2A (Cdkn2a, coding for p16Ink4), as host for endogenous mammary tumors induced by the subcutaneous implantation of medroxyprogesterone acetate (MPA, M) pellets combined with the subsequent oral administration of 7,12-dimethylbenz[a]anthracene (DMBA, D). This endogenous mouse model of HR+ mammary carcinogenesis recapitulates key immunobiological aspects of human HR+ breast cancer. Mice bearing M/D-driven tumors were allocated to RT, P or their combination in the optional presence of the CASP8 dimerizer AP20187, and monitored for tumor growth, progression-free survival and overall survival. In parallel, induction of senescence in vitro, in cultured human mammary hormone receptor (HR)+ adenocarcinoma MCF7 cells, triple negative breast carcinoma MDA-MB-231 cells and mouse HR+ mammary carcinoma TS/A cells treated with RT, P or their combination, was determined by colorimetric assessment of senescence-associated β-galactosidase activity after 3 or 7 days of treatment.

RESULTS

In vivo depletion of p16Ink4-expressing (senescent) cells ameliorated the efficacy of P→RT (but not that of RT→P) in the M/D-driven model of HR+ mammary carcinogenesis. Accordingly, P→RT induced higher levels of cellular senescence than R→TP in cultured human and mouse breast cancer cell lines.

CONCLUSIONS

Pending validation in other experimental systems, these findings suggest that a program of cellular senescence in malignant cells may explain (at least partially) the inferiority of P→RT versus RT→P in preclinical models of HR+ breast cancer.

The BRD4 inhibitor JQ1 augments the antitumor efficacy of abemaciclib in preclinical models of gastric carcinoma

BACKGROUND

Advanced gastric cancer (GC) is a lethal malignancy, harboring recurrent alterations in cell cycle pathway, especially the CDKN2A-CDK4/CDK6/CCND1 axis. However, monotherapy of CDK4/6 inhibitors has shown limited antitumor effects for GC, and combination treatments were urgently needed for CDK4/6 inhibitors.

METHODS

Here, we performed a comprehensive analysis, including drug screening, pan-cancer genomic dependency analysis, and epigenetic sequencing to identify the candidate combination with CDK4/6 inhibitors. Mechanisms were investigated by bulk RNA-sequencing and experimental validation was conducted on diverse in vitro or in vivo preclinical GC models.

RESULTS

We found that the BRD4 inhibitor JQ1 augments the antitumor efficacy of the CDK4/6 inhibitor abemaciclib (ABE). Diverse in vitro and in vivo preclinical GC models are examined and synergistic benefits from the combination therapy are obtained consistently. Mechanistically, the combination of ABE and JQ1 enhances the cell cycle arrest of GC cells and induces unique characteristics of cellular senescence through the induction of DNA damage, which is revealed by transcriptomic profiling and further validated by substantial in vitro and in vivo GC models.

CONCLUSION

This study thus proposes a candidate combination therapy of ABE and JQ1 to improve the therapeutic efficacy and worth further investigation in clinical trials for GC.

Emerging approaches to CDK inhibitor development, a structural perspective

Aberrant activity of the cyclin-dependent kinase family is frequently noted in a number of diseases identifying them as potential targets for drug development. However, current CDK inhibitors lack specificity owing to the high sequence and structural conservation of the ATP binding cleft across family members, highlighting the necessity of finding novel modes of CDK inhibition. The wealth of structural information regarding CDK assemblies and inhibitor complexes derived from X-ray crystallographic studies has been recently complemented through the use of cryo-electron microscopy. These recent advances have provided insights into the functional roles and regulatory mechanisms of CDKs and their interaction partners. This review explores the conformational malleability of the CDK subunit, the importance of SLiM recognition sites in CDK complexes, the progress made in chemically induced CDK degradation and how these studies can contribute to CDK inhibitor design. Additionally, fragment-based drug discovery can be utilised to identify small molecules that bind to allosteric sites on the CDK surface employing interactions which mimic those of native protein-protein interactions. These recent structural advances in CDK inhibitor mechanisms and in chemical probes which do not occupy the orthosteric ATP binding site can provide important insights for targeted CDK therapies.

Inhibitory Effect of Hernandezine on the Proliferation of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) causes 830000 deaths every year and is becoming the third malignant tumor worldwide. One of the primary reasons is the lack of effective drugs. Hernandezine (HER), a bisbenzylisoquinoline alkaloid of Thalictrum simplex, has been confirmed to have antitumor activity. But there are few reports about its effect on HCC and the underlying mechanisms still remain unclear. Therefore, the antitumor effects and mechanisms of HER on HCC were evaluated in HepG2 and Hep3B cells. The in vitro experiments demonstrated that HER significantly induced G0/G1 phase arrest, inhibited the proliferation and promoted cell apoptosis in liver cancer cell lines. In the mechanisms, the antitumor effects of HER on liver cancer cells were mediated by phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT) pathway and reactive oxygen species (ROS), simultaneously. In one way, HER inhibited the activities of PI3K-AKT pathway, which interrupt the dimer formation of cyclin-dependent kinase 4 (CDK4) and cyclin D1 (CCND1) and result to G0/G1 phase arrest. In another way, after HER treatment, ROS accumulated in liver cancer cells and caused mitochondria injury which further influenced the expression of apoptosis-related proteins and eventually resulted to HepG2 and Hep3B cell apoptosis. In addition, HER showed a tumor restrain function in HepG2 and Hep3B bearing nude mice. Overall, these findings indicated that HER is a promising antitumor drug, which may provide a new direction for clinical HCC treatment.

HSF1 activates the FOXO3a-ΔNp63α-CDK4 axis to promote head and neck squamous cell carcinoma cell proliferation and tumour growth

Head and neck squamous cell carcinoma (HNSCC) is one of the most prevalent cancers worldwide. Heat shock factor 1 (HSF1) is a conserved transcriptional factor that plays a critical role in maintaining cellular proteostasis. However, the role of HSF1 in HNSCC development remains largely unclear. Here, we report that HSF1 promotes forkhead box protein O3a (FOXO3a)-dependent transcription of ΔNp63α (p63 isoform in the p53 family; inhibits cell migration, invasion, and metastasis), which leads to upregulation of cyclin-dependent kinase 4 expression and HNSCC tumour growth. Ablation of HSF1 or treatment with KRIBB11, a specific pharmacological inhibitor of HSF1, significantly suppresses ΔNp63α expression and HNSCC tumour growth. Clinically, the expression of HSF1 is positively correlated with the expression of ΔNp63α in HNSCC tumours. Together, this study demonstrates that the HSF1-ΔNp63α pathway is critically important for HNSCC tumour growth.

Clear Cell Carcinoma Arising in Low-Grade Mullerian Adenosarcoma: First Reported Case with Insight into Molecular Profile

Uterine adenosarcoma (AS) is a rare biphasic neoplasm composed of a malignant, usually low-grade stromal component and benign epithelial component, usually endometrioid. Pathogenesis is unknown; some cases are undoubtably associated with tamoxifen use. Endometrial clear cell carcinoma (CCC) is an aggressive subtype of endometrial cancer, accounting for less than 10% of all uterine carcinomas. The etiology is unknown but can rarely be associated with Lynch syndrome and tamoxifen administration. The development of a composite neoplasm consisting of adenocarcinoma in AS is extremely rare. Endometrioid carcinoma typically represents the epithelial component of the composite tumor. Here we present the very first case of composite tumor, namely, AS with CCC in which next-generation sequencing was performed. Patient was an 85-year-old woman treated with tamoxifen for 5 years. To better understand the pathobiology of two tumors, a targeted genomic analysis of both components was performed. We found seven identical somatic variants in the samples of both tumors, indicating that the tumors have a high probability of having the same origin. Dual amplification of CDK4 and MDM2 was the most likely primary cause of tumor formation, but also one driver variant in the DHX15 gene that was present in both tumor components, suggesting that DHX15 may play an important role in the initiation and development of sarcoma and carcinoma. The patient is followed by regular clinical controls and is alive without signs of disease recurrence 18 months after surgery.

CDK4/6 blockade provides an alternative approach for treatment of mismatch-repair deficient tumors

Mismatch repair-deficient (dMMR) tumors show a good response toward immune checkpoint inhibitors (ICI), but developing resistance impairs patients’ outcomes. Here, we compared the therapeutic potential of an α-PD-L1 antibody with the CDK4/6 inhibitor abemaciclib in two preclinical mouse models of dMMR cancer, focusing on immune-modulatory effects of either treatment. Abemaciclib monotherapy significantly prolonged overall survival of Mlh1^−/− and Msh2^{loxP/loxP;TgTg(Vil1-cre)} mice (Mlh1^−/−: 14.5 wks vs. 9.0 wks (α-PD-L1), and 3.5 wks (control); Msh2^{loxP/loxP;TgTg(Vil1-cre)}: 11.7 wks vs. 9.6 wks (α-PD-L1), and 2.0 wks (control)). The combination was not superior to either monotherapy. PET/CT imaging revealed individual response profiles, with best clinical responses seen with abemaciclib mono- and combination therapy. Therapeutic effects were accompanied by increasing numbers of tumor-infiltrating CD4⁺/CD8⁺ T-cells and lower numbers of M2-macrophages. Levels of T cell exhaustion markers and regulatory T cell counts declined. Expression analysis identified higher numbers of dendritic cells and neutrophils within tumors together with high expression of DNA damage repair genes as part of the global stress response. In Mlh1^−/− tumors, abemaciclib suppressed the PI3K/Akt pathway and led to induction of Mxd4/Myc. The immune-modulatory potential of abemaciclib renders this compound ideal for dMMR patients not eligible for ICI treatment.

Transcription factor ZEB1 regulates PLK1-mediated SKA3 phosphorylation to promote lung cancer cell proliferation, migration and cell cycle

Lung cancer (LC) is one of the most common malignancies worldwide with low 5-year survival rate. The mechanism of spindle and kinetochore-associated complex subunit 3 (SKA3) in LC tumorgenesis remains largely unclear. The expression of SKA3 in LC cells was detected by quantitative PCR. Cell proliferation, migration and cell cycle were evaluated by functional assays including 5-ethynyl-2'-deoxyuridine, wound healing, transwell assays and flow cytometry analysis. Bioinformatics analysis, chromatin immunoprecipitation, luciferase reporter, co-immunoprecipitation and in vitro phosphorylation assays were applied to explore the interactions between zinc finger E-box binding homeobox 1 (ZEB1) and SKA3/polo-like kinase 1 (PLK1). SKA3 is highly expressed in LC cell lines and drives LC cell proliferation, migration and cell cycle. PLK1 also enhances the malignancy of LC cells. PLK1 can mediate SKA3 phosphorylation and enhance the stability of SKA3 protein, thus promoting LC progression. Besides, we found that transcription factor ZEB1 transcriptionally activates SKA3/PLK1 expression, contributing to LC cell malignancy. This study demonstrated that transcription factor ZEB1 modulates PLK1-mediated SKA3 phosphorylation to accelerate LC cell growth, migration and cycle, which might offer novel insight into LC treatment.

Targeting CDK7 in oncology: The avenue forward

Cyclin-dependent kinase (CDK) 7 is best characterized for the ability to regulate biological processes, including the cell cycle and gene transcription. Abnormal CDK7 activity is observed in various tumours and represents a driving force for tumourigenesis. Therefore, CDK7 may be an appealing target for cancer treatment. Whereas, the enthusiasm for CDK7-targeted therapeutic strategy is mitigated due to the widely possessed belief that this protein is essential for normal cells. Indeed, the fact confronts the consensus. This is the first review to introduce the role of CDK7 in pan-cancers via a combined analysis of comprehensive gene information and (pre)clinical research results. We also discuss the recent advances in protein structure and summarize the understanding of mechanisms underlying CDK7 function. These endeavours highlight the pivotal roles of CDK7 in tumours and may contribute to the development of effective CDK7 inhibitors within the strategy of structure-based drug discovery for cancer therapy.

Discovery of 3-Amino-1H-pyrazole-Based Kinase Inhibitors to Illuminate the Understudied PCTAIRE Family

The PCTAIRE subfamily belongs to the CDK (cyclin-dependent kinase) family and represents an understudied class of kinases of the dark kinome. They exhibit a highly conserved binding pocket and are activated by cyclin Y binding. CDK16 is targeted to the plasma membrane after binding to N-myristoylated cyclin Y and is highly expressed in post-mitotic tissues, such as the brain and testis. Dysregulation is associated with several diseases, including breast, prostate, and cervical cancer. Here, we used the N-(1H-pyrazol-3-yl)pyrimidin-4-amine moiety from the promiscuous inhibitor 1 to target CDK16, by varying different residues. Further optimization steps led to 43d, which exhibited high cellular potency for CDK16 (EC₅₀ = 33 nM) and the other members of the PCTAIRE and PFTAIRE family with 20-120 nM and 50-180 nM, respectively. A DSF screen against a representative panel of approximately 100 kinases exhibited a selective inhibition over the other kinases. In a viability assessment, 43d decreased the cell count in a dose-dependent manner. A FUCCI cell cycle assay revealed a G2/M phase cell cycle arrest at all tested concentrations for 43d, caused by inhibition of CDK16.

Biomarkers of Response and Resistance to CDK4/6 Inhibitors in Breast Cancer: Hints from Liquid Biopsy and microRNA Exploration

New evidence on the impact of dysregulation of the CDK4/6 pathway on breast cancer (BC) cell proliferation has led to the development of selective CDK4/6 inhibitors, which have radically changed the management of advanced BC. Despite the improved outcomes obtained by CDK4/6 inhibitors, approximately 10% of tumors show primary resistance, whereas acquired resistance appears to be an almost ubiquitous occurrence, leading to treatment failure. The identification of differentially expressed genes or genomic mutational signatures able to predict sensitivity or resistance to CDK4/6 inhibitors is critical for medical decision making and for avoiding or counteracting primary or acquired resistance against CDK4/6 inhibitors. In this review, we summarize the main mechanisms of resistance to CDK4/6 inhibitors, focusing on those associated with potentially relevant biomarkers that could predict patients' response/resistance to treatment. Recent advances in biomarker identification are discussed, including the potential use of liquid biopsy for BC management and the role of multiple microRNAs as molecular predictors of cancer cell sensitivity and resistance to CDK4/6 inhibitors.

Selective Cyclin-Dependent Kinase Inhibitors and Their Application in Cancer Therapy

Every cell cycle step is a well-regulated process controlled by cyclin-dependent kinases (CDKs). Selectivity to individual CDKs is crucial in minimizing potential off target complications. Disclosures in this Patent Highlight provides CDK2-selective inhibitor compounds and methods for treating cancers.

Identification and Analysis of Immune-Related Gene Signature in Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) originates from the hepatocytes and accounts for 90% of liver cancer. The study intends to identify novel prognostic biomarkers for predicting the prognosis of HCC patients based on TCGA and GSE14520 cohorts.

METHODS

Differential analysis was employed to obtain the DEGs (Differentially Expressed Genes) of the TCGA-LIHC-TPM cohort. The lasso regression analysis was applied to build the prognosis model through using the TCGA cohort as the training group and the GSE14520 cohort as the testing group. Next, based on the prognosis model, we performed the following analyses: the survival analysis, the independent prognosis analysis, the clinical feature analysis, the mutation analysis, the immune cell infiltration analysis, the tumor microenvironment analysis, and the drug sensitivity analysis. Finally, the survival time of HCC patients was predicted by constructing nomograms.

RESULTS

Through the lasso regression analysis, we obtained a prognosis model of ten genes including BIRC5 (baculoviral IAP repeat containing 5), CDK4 (cyclin-dependent kinase 4), DCK (deoxycytidine kinase), HSPA4 (heat shock protein family A member 4), HSP90AA1 (heat shock protein 90 α family class A member 1), PSMD2 (Proteasome 26S Subunit Ubiquitin Receptor, Non-ATPase 2), IL1RN (interleukin 1 receptor antagonist), PGF (placental growth factor), SPP1 (secreted phosphoprotein 1), and STC2 (stanniocalcin 2). First, we found that the risk score is an independent prognosis factor and is related to the clinical features of HCC patients, covering AFP (α-fetoprotein) and stage. Second, we observed that the p53 mutation was the most obvious mutation between the high-risk and low-risk groups. Third, we also discovered that the risk score is related to some immune cells, covering B cells, T cells, dendritic, macrophages, neutrophils, etc. Fourth, the high-risk group possesses a lower TIDE score, a higher expression of immune checkpoints, and higher ESTIMATE score. Finally, nomograms include the clinical features and risk signatures, displaying the clinical utility of the signature in the survival prediction of HCC patients.

CONCLUSIONS

Through the comprehensive analysis, we constructed an immune-related prognosis model to predict the survival of HCC patients. In addition to predicting the survival time of HCC patients, this model significantly correlates with the tumor microenvironment. Furthermore, we concluded that these ten immune-related genes (BIRC5, CDK4, DCK, HSPA4, HSP90AA1, PSMD2, IL1RN, PGF, SPP1, and STC2) serve as novel targets for antitumor immunity. Therefore, this study plays a significant role in exploring the clinical application of immune-related genes.

Small Extracellular Vesicles and Their Involvement in Cancer Resistance: An Up-to-Date Review

In recent years, tremendous progress has been made in understanding the roles of extracellular vesicles (EVs) in cancer. Thanks to advancements in molecular biology, it has been found that the fraction of EVs called exosomes or small EVs (sEVs) modulates the sensitivity of cancer cells to chemotherapeutic agents by delivering molecularly active non-coding RNAs (ncRNAs). An in-depth analysis shows that two main molecular mechanisms are involved in exosomal modified chemoresistance: (1) translational repression of anti-oncogenes by exosomal microRNAs (miRs) and (2) lack of translational repression of oncogenes by sponging of miRs through long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs). At the cellular level, these processes increase the proliferation and survival of cancer cells and improve their ability to metastasize and resist apoptosis. In addition, studies in animal models have shown enhancing tumor size under the influence of exosomal ncRNAs. Ultimately, exosomal ncRNAs are responsible for clinically significant chemotherapy failures in patients with different types of cancer. Preliminary data have also revealed that exosomal ncRNAs can overcome chemotherapeutic agent resistance, but the results are thoroughly fragmented. This review presents how exosomes modulate the response of cancer cells to chemotherapeutic agents. Understanding how exosomes interfere with chemoresistance may become a milestone in developing new therapeutic options, but more data are still required.

Beyond targeting amplified MDM2 and CDK4 in well differentiated and dedifferentiated liposarcomas: From promise and clinical applications towards identification of progression drivers

Well differentiated and dedifferentiated liposarcomas (WDLPS and DDLPS) are tumors of the adipose tissue poorly responsive to conventional cytotoxic chemotherapy which currently remains the standard-of-care. The dismal prognosis of the DDLPS subtype indicates an urgent need to identify new therapeutic targets to improve the patient outcome. The amplification of the two driver genes MDM2 and CDK4, shared by WDLPD and DDLPS, has provided the rationale to explore targeting the encoded ubiquitin-protein ligase and cell cycle regulating kinase as a therapeutic approach. Investigation of the genomic landscape of WD/DDLPS and preclinical studies have revealed additional potential targets such as receptor tyrosine kinases, the cell cycle kinase Aurora A, and the nuclear exporter XPO1. While the therapeutic significance of these targets is being investigated in clinical trials, insights into the molecular characteristics associated with dedifferentiation and progression from WDLPS to DDLPS highlighted additional genetic alterations including fusion transcripts generated by chromosomal rearrangements potentially providing new druggable targets (e.g. NTRK, MAP2K6). Recent years have witnessed the increasing use of patient-derived cell and tumor xenograft models which offer valuable tools to accelerate drug repurposing and combination studies. Implementation of integrated "multi-omics" investigations applied to models recapitulating WD/DDLPS genetics, histologic differentiation and biology, will hopefully lead to a better understanding of molecular alterations driving liposarcomagenesis and DDLPS progression, as well as to the identification of new therapies tailored on tumor histology and molecular profile.

The SREBP-dependent regulation of cyclin D1 coordinates cell proliferation and lipid synthesis

The sterol regulatory-element binding protein (SREBP) family of transcription factors regulates cholesterol, fatty acid, and triglyceride synthesis and metabolism. However, they are also targeted by the ubiquitin ligase Fbw7, a major tumor suppressor, suggesting that they could regulate cell growth. Indeed, enhanced lipid synthesis is a hallmark of many human tumors. Thus, the SREBP pathway has recently emerged as a potential target for cancer therapy. We have previously demonstrated that one of these transcription factors, SREBP1, is stabilized and remains associated with target promoters during mitosis, suggesting that the expression of these target genes could be important as cells enter G1 and transcription is restored. Activation of cyclin D-cdk4/6 complexes is critical for the phosphorylation and inactivation of the retinoblastoma protein (Rb) family of transcriptional repressors and progression through the G1 phase of the cell cycle. Importantly, the cyclin D-cdk4/6-Rb regulatory axis is frequently dysregulated in human cancer. In the current manuscript, we demonstrate that SREBP1 activates the expression of cyclin D1, a coactivator of cdk4 and cdk6, by binding to an E-box in the cyclin D1 promoter. Consequently, inactivation of SREBP1 in human liver and breast cancer cell lines reduces the expression of cyclin D1 and attenuates Rb phosphorylation. Rb phosphorylation in these cells can be rescued by restoring cyclin D1 expression. On the other hand, expression of active SREBP1 induced the expression of cyclin D1 and increased the phosphorylation of Rb in a manner dependent on cyclin D1 and cdk4/6 activity. Inactivation of SREBP1 resulted in reduced expression of cyclin D1, attenuated phosphorylation of Rb, and reduced proliferation. Inactivation of SREBP1 also reduced the insulin-dependent regulation of the cyclin D1 gene. At the same time, SREBP1 is known to play an important role in supporting lipid synthesis in cancer cells. Thus, we propose that the SREBP1-dependent regulation of cyclin D1 coordinates cell proliferation with the enhanced lipid synthesis required to support cell growth.

Targeting CDK4 and 6 in Cancer Therapy: Emerging Preclinical Insights Related to Abemaciclib

Pharmacologic inhibitors of cyclin-dependent kinases 4 and 6 (CDK4 and 6) are approved for the treatment of subsets of patients with hormone receptor positive (HR+) breast cancer (BC). In metastatic disease, strategies involving endocrine therapy combined with CDK4 and 6 inhibitors (CDK4 and 6i) improve clinical outcomes in HR+ BCs. CDK4 and 6i prevent retinoblastoma tumor suppressor protein phosphorylation, thereby blocking the transcription of E2F target genes, which in turn inhibits both mitogen and estrogen-mediated cell proliferation. In this review, we summarize preclinical data pertaining to the use of CDK4 and 6i in BC, with a particular focus on several of the unique chemical, pharmacologic, and mechanistic properties of abemaciclib. As research efforts elucidate the novel mechanisms underlying abemaciclib activity, potential new applications are being identified. For example, preclinical studies have demonstrated abemaciclib can exert antitumor activity against multiple tumor types and can cross the blood-brain barrier. Abemaciclib has also demonstrated distinct activity as a monotherapeutic in the treatment of BC. Accordingly, we also discuss how a greater understanding of mechanisms related to CDK4 and 6 blockade highlight abemaciclib's unique in-class properties, and could pave new avenues for enhancing its therapeutic efficacy.

Combining a CDK4/6 Inhibitor With Pemetrexed Inhibits Cell Proliferation and Metastasis in Human Lung Adenocarcinoma

Background

Recent clinical trials of cyclin-dependent kinase 4/6 inhibitors (CDK4/6i) in human lung adenocarcinoma (LUAD) have not achieved satisfactory results. The disappointing results of single-drug treatments have prompted studies about synergistic therapies of CDK4/6i with other drugs. We aimed to test the anti-tumor effect of ribociclib (a CDK4/6i) combined with pemetrexed on LUAD and the potential mechanisms.

Methods

Cell lines were exposed to ribociclib and pemetrexed at different doses. Antitumor effects were measured using growth inhibition. Cell cycle distribution and apoptosis were evaluated using flow cytometry. Cell migration and invasion were measured using wound healing and transwell invasion assays, respectively. The expression levels of proteins were analyzed using western blotting. Mice xenograft models were used for validation in vivo.

Results

Synergism was associated with a combination of cell cycle effects from both agents. Cell cycle analysis revealed that pemetrexed blocked cells in the S phase, whereas ribociclib arrested cells in the G1 phase. Concomitant treatment with pemetrexed and ribociclib resulted in a significantly stronger antitumor ability than treatment alone. We also found that ribociclib strongly enhanced the pro-apoptotic activity of pemetrexed via the caspase/bcl-2 signaling pathway. In addition, we report for the first time that combination treatment with ribociclib and pemetrexed significantly inhibits the migration and invasion of LUAD cells.

Conclusions

Combining ribociclib and pemetrexed showed a powerful ability to inhibit cancer proliferation, invasion, and metastasis, and it holds potential as a novel effective combinative therapy for patients with LUAD.