CDK6-PI3K signaling axis is an efficient target for attenuating ABCB1/P-gp mediated multi-drug resistance (MDR) in cancer cells

Double Swords in One: Novel Selective PI3K/110β PROTAC Degraders for the Treatment of Multidrug-Resistant Cancer by Activating ERS and Inhibiting P-gp

The p110β isoform of the PI3 kinase (PI3K) family plays a key role in tumorigenesis and PTEN loss-driven multidrug resistance (MDR). Herein, we describe the design, synthesis, and structure-activity relationship studies of a series of small-molecule PI3K/110β PROTACs degraders by combining the selective inhibitor TGX221 of PI3K/110β with VHL ligands. Among them, J-6 and J-9 exhibited rapid and efficient degradation ability for the target proteins in MDR cells. Meanwhile, the expression and activity of P-glycoprotein were significantly inhibited, leading to a strong synergistic antitumor effect with adriamycin or cisplatin. Further studies confirmed that the two degraders can induce endoplasmic reticulum stress-mediated mitochondrial apoptosis by the AKT/Bcl-2 inhibition-mediated PERK/CHOP-unfolded protein reaction. In vivo studies also verified that the two degraders inhibited the growth of MCF-7/ADM xenograft tumors with high safety. Hence, this study and further optimization of these PI3K/110β PROTAC degraders have broad prospects for the development of new cancer therapies.

Preclinical studies of the falnidamol as a highly potent and specific active ABCB1 transporter inhibitor

BACKGROUND

ABCB1 overexpression is a key factor in causing multidrug resistance (MDR). As a result, it is crucial to discover effective medications against ABCB1 to overcome MDR. Falnidamol, a tyrosine kinase inhibitor (TKI) targeting the epidermal growth factor receptor (EGFR), is currently in phase 1 clinical trials for the treatment of solid tumors. In this work, we assessed whether falnidamol could act as an inhibitor of ABCB1 to reverse ABCB1-mediated MDR.

METHODS

The reversal effect of falnidamol on MDR was assessed by MTT, colony formation, 3D microsphere, and xenograft model assays. The protein expression or cellular localization was tested by western blot and immunofluorescence analysis. The intracellular doxorubicin accumulation and efflux were assessed by flow cytometry. The ATPase activity of ABCB1 was detected by a microplate reader. The interaction between falnidamol and ABCB1 was evaluated by docking analysis and cellular thermal shift assay.

RESULTS

Our data showed that falnidamol specifically reversed ABCB1-mediated MDR but not ABCG2-mediated MDR in vitro and in vivo. Mechanistic studies suggested falnidamol had no effect on ABCB1 expression or cellular localization, nor on the AKT or ERK pathways. Further studies found that falnidamol reduced ABCB1's efflux function, resulting in enhanced intracellular agent accumulation and thus overcoming MDR. ATPase assay showed that falnidamol suppressed the ABCB1 ATPase activity. Furthermore, docking analysis and cellular thermal shift assay indicated that falnidamol bound directly to the drug-binding site of ABCB1 transporter.

CONCLUSION

The present study proves that falnidamol acts as a highly potent and specific active ABCB1 transporter inhibitor, and can reverse ABCB1-mediated MDR, implying that combining falnidamol with ABCB1 substrate chemotherapeutic agents has the potential to overcome ABCB1-mediated MDR.

Multidrug Resistance Reversed by Maleimide Interactions. A Biological and Synthetic Overview for an Emerging Field

Multidrug Resistance (MDR) can be considered one of the most frightening adaptation types in bacteria, fungi, protozoa, and eukaryotic cells. It allows the organisms to survive the attack of many drugs used in the daily basis. This forces the development of new and more complex, highly specific drugs to fight diseases. Given the high usage of medicaments, poor variation in active chemical cores, and self-medication, the appearance of MDR is more frequent each time, and has been established as a serious medical and social problem. Over the years it has been possible the identification of several genes and proteins responsible for MDR and with that the development of blockers of them to reach MDR reversion and try to avoid a global problem. These mechanisms also have been observed in cancer cells, and several calcium channel blockers have been successful in MDR reversion, and the maleimide can be found included in them. In this review, we explore particularly the tree main proteins involved in cancer chemoresistance, MRP1 (encoded by ABCC1), BCRP (encoded by ABCG2) and P-gp (encoded by ABCB1). The participation of P-gp is remarkably important, and several aspects of its regulations are discussed. Additionally, we address the history, mechanisms, reversion efforts, and we specifically focused on the maleimide synthesis as MDR-reversers in co-administration, as well as on how their biological applications are imperative to expand the available information and explore a very plausible MDR reversion source.

Despicable role of epithelial-mesenchymal transition in breast cancer metastasis: Exhibiting de novo restorative regimens

Breast cancer (BC) is the most prevalent cancer in women globally. Anti-cancer advancements have enabled the killing of BC cells through various therapies; however, cancer relapse is still a major limitation and decreases patient survival and quality of life. Epithelial-to-mesenchymal transition (EMT) is responsible for tumor relapse in several cancers. This highly regulated event causes phenotypic, genetic, and epigenetic changes in the tumor microenvironment (TME). This review summarizes the recent advancements regarding EMT using de-differentiation and partial EMT theories. We extensively review the mechanistic pathways, TME components, and various anti-cancer adjuvant and neo-adjuvant therapies responsible for triggering EMT in BC tumors. Information regarding essential clinical studies and trials is also discussed. Furthermore, we also highlight the recent strategies targeting various EMT pathways. This review provides a holistic picture of BC biology, molecular pathways, and recent advances in therapeutic strategies.

PFOS and Its Commercial Alternative, 6:2 Cl-PFESA, Induce Multidrug Resistance in Pancreatic Cancer

Per- and polyfluoroalkyl substances (PFAS), specifically perfluorooctanesulfonate (PFOS) and its alternative, 2-[(6-chloro-1,1,2,2,3,3,4,4,5,5,6,6-dodecafluorohexyl)oxy]-1,1,2,2-tetrafluoroethanesulfonic acid (6:2 Cl-PFESA), are associated with environmental health concerns and potential cancer progression. However, their impact on multidrug resistance (MDR) in pancreatic cancer (PC) chemotherapy remains unclear. Here, we employed drug-sensitivity assays, including IC50 calculations, in vitro and in vivo models with various chemotherapeutics, and paclitaxel (PTX) as a representative agent, combined with transcriptomic/proteomic sequencing and clinical prognostic analysis, to identify MDR-related genes and validate their relevance, with the objective of establishing the correlation between PFOS/6:2 Cl-PFESA exposure and MDR in PC at molecular, cellular, and animal model levels. Our findings demonstrate that PFOS/6:2 Cl-PFESA exposure increases the drug IC50 in three different PC cell lines for various chemotherapeutic agents. Compared with PFOS, 6:2 Cl-PFESA demonstrated a more pro-MDR effect on PC cells in vitro. In vivo experiments further revealed that PFOS/6:2 Cl-PFESA exposures significantly reduced the efficacy of PTX in PC, with inhibition rates dropping from 78.3% to 23.8%/6.1%, respectively (p < 0.05). This effect was driven by the aberrant activation of the PI3K-ABCB1 pathway, with 6:2 Cl-PFESA demonstrating a stronger capacity to promote this signal pathway's expression and function compared with PFOS. These data suggest that exposure to PFAS may elevate the risk of MDR and subsequent disease progression. Although marketed as a safer alternative to PFOS, the notable impact of 6:2 Cl-PFESA on MDR highlights the necessity for a comprehensive assessment of its potential carcinogenic risks.

Overcoming drug resistance through extracellular vesicle-based drug delivery system in cancer treatment

Drug resistance is a major challenge in cancer therapy that often leads to treatment failure and disease relapse. Despite advancements in chemotherapeutic agents and targeted therapies, cancers often develop drug resistance, making these treatments ineffective. Extracellular vesicles (EVs) have gained attention for their potential applications in drug delivery because of their natural origin, biocompatibility, and ability to cross biological barriers. Using the unique properties of EVs could enhance drug accumulation at target sites, minimize systemic toxicity, and precisely target specific cells. Here, we discuss the characteristics and functionalization of EVs, the mechanisms of drug resistance, and the applications of engineered EVs to overcome drug resistance. This review provides a comprehensive overview of the advancements in EV-based drug delivery systems and their applications in overcoming cancer drug resistance. We highlight the potential of EV-based drug delivery systems to revolutionize cancer therapy and offer promising strategies for more effective treatment modalities.

Innovative Nanomedicine Delivery: Targeting Tumor Microenvironment to Defeat Drug Resistance

Nanodrug delivery systems have revolutionized tumor therapy like never before. By overcoming the complexity of the tumor microenvironment (TME) and bypassing drug resistance mechanisms, nanotechnology has shown great potential to improve drug efficacy and reduce toxic side effects. This review examines the impact of the TME on drug resistance and recent advances in nanomedicine delivery systems to overcome this challenge. Characteristics of the TME such as hypoxia, acidity, and high interstitial pressure significantly reduce the effectiveness of chemotherapy and radiotherapy, leading to increased drug resistance in tumor cells. Then, this review summarizes innovative nanocarrier designs for these microenvironmental features, including hypoxia-sensitive nanoparticles, pH-responsive carriers, and multifunctional nanosystems that enable targeted drug release and improved drug penetration and accumulation in tumors. By combining nanotechnology with therapeutic strategies, this review offers a novel perspective by focusing on the innovative design of nanocarriers that interact with the TME, a dimension often overlooked in similar reviews. We highlight the dual role of these nanocarriers in therapeutic delivery and TME modulation, emphasize their potential to overcome drug resistance, and look at future research directions.

CD7-targeting pro-apoptotic extracellular vesicles: A novel approach for T-cell haematological malignancy therapy

T-cell haematological malignancies progress rapidly and have a high mortality rate and effective treatments are still lacking. Here, we developed a drug delivery system utilizing 293T cell-derived extracellular vesicles (EVs) modified with an anti-CD7 single-chain variable fragment (αCD7/EVs). Given the challenges of chemotherapy resistance in patients with T-cell malignancy, we selected cytochrome C (CytC) and Bcl2 siRNA (siBcl2) as therapeutic agents and loaded them into αCD7/EVs (αCD7/EVs/CytC/siBcl2). We found that αCD7/EVs efficiently targeted and were internalized by human T-ALL Molt-4 cells. In addition, the interaction between αCD7 and CD7 switched the EV entry pathway in Molt-4 cells from macropinocytosis-dependent endocytosis to clathrin-mediated endocytosis, thereby reducing EV-lysosome colocalization, ultimately improving CytC delivery efficiency and increasing the cytotoxicity of nascent EVs from EV-treated Molt-4 cells. Notably, αCD7/EVs/CytC/siBcl2 demonstrated similar efficacy against both Molt-4 and chemotherapy-resistant Molt-4 cells (CR-Molt-4). Furthermore, αCD7/EVs/CytC/siBcl2 exhibited high safety, low immunogenicity and minimal impact on human T cells. Therefore, αCD7/EVs/CytC/siBcl2 are promising therapeutic approaches for treating CD7+ T-cell malignancies.

VASH2 enhances KIF3C-mediated EGFR-endosomal recycling to promote aggression and chemoresistance of lung squamous cell carcinoma by increasing tubulin detyrosination

Lung squamous cell carcinoma (LUSC) is associated with high mortality and has few therapeutic options. Chemotherapy remains the main treatment for LUSC patients, but multi-drug resistance has become the dominant challenge in the failure of chemotherapy in various cancers. Therefore, the effective therapeutic strategy for LUSC patients is an urgent unmet need. Here, we found vasohibin-2 (VASH2) was a prognostic biomarker for LUSC patients, and VASH2 promoted the malignant biological behaviors of LUSC cells and chemoresistance by increasing the detyrosination of α-tubulin. The high level of detyrosinated-tubulin was negatively associated with patient prognosis. Blocking the tubulin carboxypeptidase (TCP) activity of VASH2 inhibited the xenograft tumor growth and improved the treatment efficacy of paclitaxel in vivo. Results revealed that VASH2-induced increase in tubulin detyrosination boosted the binding of kinesin family member 3C (KIF3C) to microtubules and enhanced KIF3C-dependent endosomal recycling of EGFR, leading to the prolonged activation of PI3K/Akt/mTOR signaling. This study demonstrated that VASH2 was not only a prognostic biomarker but also a promising therapeutic target in LUSC, which offers a novel insight that combination of chemotherapy and EpoY, a TCP inhibitor, may be a promising treatment strategy for LUSC patients.

IGFBP7 regulates cell proliferation and migration through JAK/STAT pathway in gastric cancer and is regulated by DNA and RNA methylation

New biomarkers for early diagnosis of gastric cancer (GC), the second leading cause of cancer-related death, are urgently needed. IGFBP7, known to play various roles in multiple tumours, is complexly regulated across diverse cancer types, as evidenced by our pancancer analysis. Bioinformatics analysis revealed that IGFBP7 expression was related to patient prognosis, tumour clinicopathological characteristics, tumour stemness, microsatellite instability and immune cell infiltration, as well as the expression of oncogenes and immune checkpoints. GSEA links IGFBP7 to several cancer-related pathways. IGFBP7 deficiency inhibited GC cell proliferation and migration in vitro. Furthermore, an in vivo nude mouse model revealed that IGFBP7 downregulation suppressed the tumorigenesis of GC cells. Western blotting analysis showed that the JAK1/2-specific inhibitor ruxolitinib could rescue alterations induced by IGFBP7 overexpression in GC cells. Additionally, our bioinformatics analysis and in vitro assays suggested that IGFBP7 is regulated by DNA methylation at the genetic level and that the RNA m6A demethylase FTO modulates it at the posttranscriptional level. This study emphasizes the clinical relevance of IGFBP7 in GC and its influence on cell proliferation and migration via the JAK/STAT signalling pathway. This study also highlights the regulation of IGFBP7 in GC by DNA and m6A RNA methylation.

Novel insight into mitochondrial dynamin-related protein-1 as a new chemo-sensitizing target in resistant cancer cells

Mitochondrial dynamics have pillar roles in several diseases including cancer. Cancer cell survival is monitored by mitochondria which impacts several cellular functions such as cell metabolism, calcium signaling, and ROS production. The equilibrium of death and survival rate of mitochondria is important for healthy cellular processes. Whereas inhibition of mitochondrial metabolism and dynamics can have crucial regulatory decisions between cell survival and death. The steady rate of physiological flux of both mitochondrial fission and fusion is strongly related to the preservation of cellular bioenergetics. Dysregulation of mitochondrial dynamics including fission and fusion is a critical machinery in cells accompanied by crosstalk in cancer progression and resistance. Many cancer cells express high levels of Drp-1 to induce cancer cell invasion, metastasis and chemoresistance including breast cancer, liver cancer, pancreatic cancer, and colon cancer. Targeting Drp-1 by inhibitors such as Midivi-1 helps to enhance the responsiveness of cancer cells towards chemotherapy. The review showed Drp-1 linked processes such as mitochondrial dynamics and relationship with cancer, invasion, and chemoresistance along with computational assessing of all publicly available Drp-1 inhibitors. Drp1-IN-1, Dynole 34-2, trimethyloctadecylammonium bromide, and Schaftoside showed potential inhibitory effects on Drp-1 as compared to standard Mdivi- 1. This emerging approach may have extensive strength in the context of cancer development and chemoresistance and further work is needed to aid in more effective cancer management.

Diallyl disulfide antagonizes DJ-1 mediated proliferation, epithelial-mesenchymal transition, and chemoresistance in gastric cancer cells

Diallyl disulfide (DADS), an organic component of allicin abstracted from garlic, possesses multi-target antitumor activity. DJ-1 performs a vital function in promoting AKT aberrant activation via down-regulating phosphatase and tensin homologue (PTEN) in tumors. It is unknown the involvement of DJ-1 in epithelial-mesenchymal transition (EMT) of gastric cancer (GC) cells. The purpose of this study is to investigate whether diallyl disulfide (DADS) intervenes in the role of DJ-1 in GC. Based on the identification that the correlation between high DJ-1 and low PTEN expression in GC was implicated in clinical progression, we illuminated that down-regulation of DJ-1 by DADS aided in an increase in PTEN expression and a decrease in phosphorylated AKT levels, which was in line with the results manifested in the DJ-1 knockdown and overexpressed cells, concurrently inhibiting proliferation, EMT, migration, and invasion. Furthermore, the antagonistic effects of DADS on DJ-1 were observed in in vivo experiments. Additionally, DADS mitigated the DJ-1-associated drug resistance. The current study revealed that DJ-1 is one of potential targets for DADS, which hopefully provides a promising strategy for prevention and adjuvant chemotherapy of GC.

Ginsenoside Rg3 combined with near-infrared photothermal reversal of multidrug resistance in breast cancer MCF-7/ADR cells

Adriamycin (ADR) is a frequently employed chemotherapeutic agent for the management of breast cancer. Nevertheless, multidrug resistance (MDR) can impair its therapeutic efficacy in breast cancer. MDR is characterized by increased expression of the P-glycoprotein (P-gp) efflux pump, up-regulation of anti-apoptotic proteins, and downregulation of pro-apoptotic proteins. Consequently, inhibition of ATP-binding cassette (ABC) transporter proteins has been deemed the most efficacious approach to overcome MDR. In this study, we used MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide), Western blots, flow cytometry, immunofluorescence, and constructed xenograft tumors to investigate whether ginsenoside Rg3-near-infrared photothermal (Rg3-NIR) combination reversed multidrug resistance in MCF-7/ADR breast cancer. In vivo and in vitro experiments, the results showed that Rg3-NIR co-treatment was effective in inducing the apoptosis of MCF-7/ADR breast cancer cells. This was achieved by reversing the expression of drug resistance-associated proteins, while also inhibiting cell proliferation, migration, and epithelial-mesenchymal transition (EMT) processes via attenuation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway transduction. Ginsenoside Rg3 combined with near-infrared photothermal therapy (NIR) effectively reverses multidrug resistance in breast cancer MCF-7/ADR cells, providing a new therapeutic strategy for breast cancer drug resistance.

Alkaliptosis induction counteracts paclitaxel-resistant ovarian cancer cells via ATP6V0D1-mediated ABCB1 inhibition

Paclitaxel serves as the cornerstone chemotherapy for ovarian cancer, yet its prolonged administration frequently culminates in drug resistance, presenting a substantial challenge. Here we reported that inducing alkaliptosis, rather than apoptosis or ferroptosis, effectively overcomes paclitaxel resistance. Mechanistically, ATPase H+ transporting V0 subunit D1 (ATP6V0D1), a key regulator of alkaliptosis, plays a pivotal role by mediating the downregulation of ATP-binding cassette subfamily B member 1 (ABCB1), a multidrug resistance protein. Both ATP6V0D1 overexpression through gene transfection and pharmacological enhancement of ATP6V0D1 protein stability using JTC801 effectively inhibit ABCB1 upregulation, resulting in growth inhibition in drug-resistant cells. Additionally, increasing intracellular pH to alkaline (pH 8.5) via sodium hydroxide application suppresses ABCB1 expression, whereas reducing the pH to acidic conditions (pH 6.5) with hydrochloric acid amplifies ABCB1 expression in drug-resistant cells. Collectively, these results indicate a potentially effective therapeutic strategy for targeting paclitaxel-resistant ovarian cancer by inducing ATP6V0D1-dependent alkaliptosis.

Role and recent progress of P2Y12 receptor in cancer development

P2Y12 receptor (P2Y12R) is an adenosine-activated G protein-coupled receptor (GPCR) that plays a central role in platelet function, hemostasis, and thrombosis. P2Y12R activation can promote platelet aggregation and adhesion to cancer cells, promote tumor angiogenesis, and affect the tumor immune microenvironment (TIME) and tumor drug resistance, which is conducive to the progression of cancers. Meanwhile, P2Y12R inhibitors can inhibit this effect, suggesting that P2Y12R may be a potential therapeutic target for cancer. P2Y12R is involved in cancer development and metastasis, while P2Y12R inhibitors are effective in inhibiting cancer. However, a new study suggests that long-term use of P2Y12R inhibitors may increase the risk of cancer and the mechanism remains to be explored. In this paper, we reviewed the structural and functional characteristics of P2Y12R and its role in cancer. We explored the role of P2Y12R inhibitors in different tumors and the latest advances by summarizing the basic and clinical studies on the effects of P2Y12R inhibitors on tumors.

Guanine-Rich RNA Sequence Binding Factor 1 Deficiency Promotes Colorectal Cancer Progression by Regulating PI3K/AKT Signaling Pathway

Background

Guanine-rich RNA sequence binding factor 1 (GRSF1), part of the RNA-binding protein family, is now attracting interest due to its potential association with the progression of a variety of human cancers. The precise contribution and molecular mechanism of GRSF1 to colorectal cancer (CRC) progression, however, have yet to be clarified.

Methods

Immunohistochemistry and Western Blot analysis was carried out to detect the expression of GRSF1 in CRC at both mRNA and protein levels and its subsequent effects on prognosis. A series of functional tests were performed to understand its influence on proliferation, migration, and invasion of CRC cells.

Results

The universal downregulation of GRSF1 in CRC was identified, indicating a correlation with poor prognosis. Our functional studies unveiled that the elimination of GRSF1 enhances tumour activities such as proliferation, migration, and invasion of CRC cells, while GRSF1 overexpression curtailed these abilities.

Conclusion

Notably, we uncovered that GRSF1 insufficiency modulates the PI3K/Akt signaling pathway and Ras activation in CRC. Therefore, our data suggest GRSF1 operates as a tumor suppressor gene in CRC and may offer promise as a potential biomarker and novel therapeutic target in CRC management.

Natural products reverse cancer multidrug resistance

Cancer stands as a prominent global cause of death. One of the key reasons why clinical tumor chemotherapy fails is multidrug resistance (MDR). In recent decades, accumulated studies have shown how Natural Product-Derived Compounds can reverse tumor MDR. Discovering novel potential modulators to reduce tumor MDR by Natural Product-Derived Compounds has become a popular research area across the globe. Numerous studies mainly focus on natural products including flavonoids, alkaloids, terpenoids, polyphenols and coumarins for their MDR modulatory activity. Natural products reverse MDR by regulating signaling pathways or the relevant expressed protein or gene. Here we perform a deep review of the previous achievements, recent advances in the development of natural products as a treatment for MDR. This review aims to provide some insights for the study of multidrug resistance of natural products.

Plk3 Enhances Cisplatin Sensitivity of Nonsmall-Cell Lung Cancer Cells through Inhibition of the PI3K/AKT Pathway via Stabilizing PTEN

Polo-like kinase 3 (Plk3) is involved in tumor development with a tumor suppressive function. However, the effect of Plk3 on the chemoresistance remains unclear. It has been documented that activation of the PI3K/AKT signaling pathway by PTEN loss significantly enhances chemoresistance in nonsmall-cell lung cancer (NSCLC). This study aims to evaluate the PTEN regulation by Plk3 and identify targets and underlying mechanisms that could be used to relieve chemoresistance. Our results showed that silencing Plk3 reduced PTEN expression and activated PI3K/AKT signaling by dephosphorylating and destabilizing PTEN in NSCLC cells. Reducing Plk3 expression promoted drug resistance to cisplatin (DDP), while overexpressing Plk3 promoted DDP sensitivity. However, these effects were attenuated when MK2206, a PI3K/AKT inhibitor, was applied. In conclusion, upregulation of Plk3 sensitized NSCLC cells toward DDP, which provides a potential target to restore DDP chemoresponse. We provided novel evidence that the PTEN/PI3K/AKT signaling pathway could be regulated by Plk3 through phosphorylation of PTEN and highlighted the critical role of Plk3 in the DDP resistance of NSCLC.

Potential Target of CDK6 Signaling Pathway for Cancer Treatment

BACKGROUND

Cancer involves uncontrolled cell growth due to genetic mutations. Tumors can form when CDK6, a gene essential for controlling cell growth, isn't working correctly. Researchers are investigating drugs that inhibit CDK6; some of them appear promising. Nevertheless, CDK6 is advantageous and harmful to cancer because it controls other cellular processes. By inhibiting CDK6 and CDK4, CDK4/6 inhibitors offer a novel therapeutic strategy that stops cell proliferation. The study investigates the function of CDK6 in cancer, the difficulties in targeting CDK6, and possible remedies.

OBJECTIVE

Scientists have developed drugs designed to block CDK6 and prevent it from altering other proteins. These drugs, also known as CDK6 inhibitors, help treat cancer. Finding the best drugs for CDK6 is still tricky, though. The drugs' selectivity, potency, and cost are some difficulties. These factors depend on CDK6's structure and interactions with other proteins. The structure of CDK6 and how it influences its function and regulation are explained in this review. It also describes CDK6's function in cancer and its interaction with other molecules and proteins, which is crucial for cell division. This review also discusses the present and upcoming therapies that target CDK6, as well as how CDK6 interacts with drugs that block it.

CONCLUSION

This review presents the structure, current research, and overview of CDK6. It also reviews the role of CDK6 in cancer, function, and regulation. Additionally, it explores its role in cancer signaling networks and its interaction with CDK6 inhibitors. Lastly, it discusses the current status and prospects of therapies targeting CDK6.

Supramolecular host-guest nanosystems for overcoming cancer drug resistance

Cancer drug resistance has become one of the main challenges for the failure of chemotherapy, greatly limiting the selection and use of anticancer drugs and dashing the hopes of cancer patients. The emergence of supramolecular host-guest nanosystems has brought the field of supramolecular chemistry into the nanoworld, providing a potential solution to this challenge. Compared with conventional chemotherapeutic platforms, supramolecular host-guest nanosystems can reverse cancer drug resistance by increasing drug uptake, reducing drug efflux, activating drugs, and inhibiting DNA repair. Herein, we summarize the research progress of supramolecular host-guest nanosystems for overcoming cancer drug resistance and discuss the future research direction in this field. It is hoped that this review will provide more positive references for overcoming cancer drug resistance and promoting the development of supramolecular host-guest nanosystems.

Mechanism of multidrug resistance to chemotherapy mediated by P‑glycoprotein (Review)

Multidrug resistance (MDR) seriously limits the clinical application of chemotherapy. A mechanism underlying MDR is the overexpression of efflux transporters associated with chemotherapeutic drugs. P‑glycoprotein (P‑gp) is an ATP‑binding cassette (ABC) transporter, which promotes MDR by pumping out chemotherapeutic drugs and reducing their intracellular concentration. To date, overexpression of P‑gp has been detected in various types of chemoresistant cancer and inhibiting P‑gp‑related MDR has been suggested. The present review summarizes the mechanisms underlying MDR mediated by P‑gp in different tumors and evaluated the related signaling pathways, with the aim of improving understanding of the current status of P‑gp‑mediated chemotherapeutic resistance. This review focuses on the main mechanisms of inhibiting P‑gp‑mediated MDR, with the aim of providing a reference for the study of reversing P‑gp‑mediated MDR. The first mechanism involves decreasing the efflux activity of P‑gp by altering its conformation or hindering P‑gp‑chemotherapeutic drug binding. The second inhibitory mechanism involves inhibiting P‑gp expression to reduce efflux. The third inhibitory mechanism involves knocking out the ABCB1 gene. Potential strategies that can inhibit P‑gp include certain natural products, synthetic compounds and biological techniques. It is important to screen lead compounds or candidate techniques for P‑gp inhibition, and to identify inhibitors by targeting the relevant signaling pathways to overcome P‑gp‑mediated MDR.

Tumor microenvironment diversity and plasticity in cancer multidrug resistance

Multidrug resistance (MDR) poses a significant obstacle to effective cancer treatment, and the tumor microenvironment (TME) is crucial for MDR development and reversal. The TME plays an active role in promoting MDR through several pathways. However, a promising therapeutic approach for battling MDR involves targeting specific elements within the TME. Therefore, this comprehensive review elaborates on the research developments regarding the dual role of the TME in promoting and reversing MDR in cancer. Understanding the complex role of the TME in promoting and reversing MDR is essential to developing effective cancer therapies. Utilizing the adaptability of the TME by targeting novel TME-specific factors, utilizing combination therapies, and employing innovative treatment strategies can potentially combat MDR and achieve personalized treatment outcomes for patients with cancer.

Hexavalent Chromium Inhibited Zebrafish Embryo Development by Altering Apoptosis- and Antioxidant-Related Genes

This study aimed to assess the effects of hexavalent chromium on zebrafish (Danio rerio) embryo development. The zebrafish embryos were treated with solutions containing chromium at different concentrations (0.1, 1, 3.125, 6.25, 12.5, 50, and 100 µg/mL). The development of zebrafish embryos was estimated by the determination of survival rate, heart rate, and the measurement of larvae body length. Real time RT-PCR and Western blot were performed to assess the expression of apoptosis- and antioxidant-related genes. The results showed that the reduced survival rate of zebrafish embryos and larvae was associated with an increase in chromium concentration. The exposure of higher concentrations resulted in a decrease in body length of zebrafish larvae. In addition, a marked increase in heart rate was observed in the zebrafish larvae under chromium treatment, especially at high concentrations. The real-time RT-PCR analysis showed that the transcript expressions for cell-cycle-related genes (cdk4 and cdk6) and antioxidant-related genes (sod1 and sod2) were downregulated in the zebrafish embryos treated with chromium. Western blot analysis revealed the upregulation of Caspase 3 and Bax, while a downregulation was observed in Bcl2. These results indicated that hexavalent chromium induced changes in zebrafish embryo development by altering apoptosis- and antioxidant-related genes.

CDK4/6 Inhibitor Resistance in Hormone Receptor-Positive Metastatic Breast Cancer: Translational Research, Clinical Trials, and Future Directions

The emergence of CDK4/6 inhibitors, such as palbociclib, ribociclib, and abemaciclib, has revolutionized the treatment landscape for hormone receptor-positive breast cancer. These agents have demonstrated significant clinical benefits in terms of both progression-free survival and overall survival. However, resistance to CDK4/6 inhibitors remains a challenge, limiting their long-term efficacy. Understanding the complex mechanisms driving resistance is crucial for the development of novel therapeutic strategies and the improvement of patient outcomes. Translational research efforts, such as preclinical models and biomarker studies, offer valuable insight into resistance mechanisms and may guide the identification of novel combination therapies. This review paper aims to outline the reported mechanisms underlying CDK4/6 inhibitor resistance, drawing insights from both clinical data and translational research in order to help direct the future of treatment for hormone receptor-positive metastatic breast cancer.

Functionalized nanoparticles crossing the brain-blood barrier to target glioma cells

Glioma is the most common tumor of the central nervous system (CNS), with a 5-year survival rate of <35%. Drug therapy, such as chemotherapeutic and immunotherapeutic agents, remains one of the main treatment modalities for glioma, including temozolomide, doxorubicin, bortezomib, cabazitaxel, dihydroartemisinin, immune checkpoint inhibitors, as well as other approaches such as siRNA, ferroptosis induction, etc. However, the filter function of the blood-brain barrier (BBB) reduces the amount of drugs needed to effectively target CNS tumors, making it one of the main reasons for poor drug efficacies in glioma. Thus, finding a suitable drug delivery platform that can cross the BBB, increase drug aggregation and retainment in tumoral areas and avoid accumulation in non-targeted areas remains an unsolved challenge in glioma drug therapy. An ideal drug delivery system for glioma therapy should have the following features: (1) prolonged drug life in circulation and effective penetration through the BBB; (2) adequate accumulation within the tumor (3) controlled-drug release modulation; (4) good clearance from the body without significant toxicity and immunogenicity, etc. In this regard, due to their unique structural features, nanocarriers can effectively span the BBB and target glioma cells through surface functionalization, providing a new and effective strategy for drug delivery. In this article, we discuss the characteristics and pathways of different nanocarriers for crossing the BBB and targeting glioma by listing different materials for drug delivery platforms, including lipid materials, polymers, nanocrystals, inorganic nanomaterials, etc.

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.

Intact regulation of G1/S transition renders esophageal squamous cell carcinoma sensitive to PI3Kα inhibitors

Phosphatidylinositol 3-kinase alpha (PI3Kα) inhibitors are currently evaluated for the therapy of esophageal squamous cell carcinoma (ESCC). It is of great importance to identify potential biomarkers to predict or monitor the efficacy of PI3Kα inhibitors in an aim to improve the clinical responsive rate in ESCC. Here, ESCC PDXs with CCND1 amplification were found to be more sensitive to CYH33, a novel PI3Kα-selective inhibitor currently in clinical trials for the treatment of advanced solid tumors including ESCC. Elevated level of cyclin D1, p21 and Rb was found in CYH33-sensitive ESCC cells compared to those in resistant cells. CYH33 significantly arrested sensitive cells but not resistant cells at G1 phase, which was associated with accumulation of p21 and suppression of Rb phosphorylation by CDK4/6 and CDK2. Hypo-phosphorylation of Rb attenuated the transcriptional activation of SKP2 by E2F1, which in turn hindered SKP2-mediated degradation of p21 and reinforced accumulation of p21. Moreover, CDK4/6 inhibitors sensitized resistant ESCC cells and PDXs to CYH33. These findings provided mechanistic rationale to evaluate PI3Kα inhibitors in ESCC patients harboring amplified CCND1 and the combined regimen with CDK4/6 inhibitors in ESCC with proficient Rb.

CRISPR/Cas9-based Gene Therapies for Fighting Drug Resistance Mediated by Cancer Stem Cells

Cancer stem cells (CSCs) are cancer-initiating cells found in most tumors and hematological cancers. CSCs are involved in cells progression, recurrence of tumors, and drug resistance. Current therapies have been focused on treating the mass of tumor cells and cannot eradicate the CSCs. CSCs drug-specific targeting is considered as an approach to precisely target these cells. Clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) gene-editing systems are making progress and showing promise in the cancer research field. One of the attractive applications of CRISPR/Cas9 as one approach of gene therapy is targeting the critical genes involved in drug resistance and maintenance of CSCs. The synergistic effects of gene editing as a novel gene therapy approach and traditional therapeutic methods, including chemotherapy, can resolve drug resistance challenges and regression of the cancers. This review article considers different aspects of CRISPR/Cas9 ability in the study and targeting of CSCs with the intention to investigate their application in drug resistance.

Current Status and Prospects of Targeted Therapy for Osteosarcoma

Osteosarcoma (OS) is a highly malignant tumor occurring in bone tissue with a high propensity to metastasize, and its underlying mechanisms remain largely elusive. The OS prognosis is poor, and improving the survival of OS patients remains a challenge. Current treatment methods such as surgical approaches, chemotherapeutic drugs, and immunotherapeutic drugs remain ineffective. As research progresses, targeted therapy is gradually becoming irreplaceable. In this review, several treatment modalities for osteosarcoma, such as surgery, chemotherapy, and immunotherapy, are briefly described, followed by a discussion of targeted therapy, the important targets, and new technologies for osteosarcoma treatment.

Perspectives of metal-organic framework nanosystem to overcome tumor drug resistance

Cancer is one of the most harmful diseases in the world, which causes huge numbers of deaths every year. Many drugs have been developed to treat tumors. However, drug resistance usually develops after a period of time, which greatly weakens the therapeutic effect. Tumor drug resistance is characterized by blocking the action of anticancer drugs, resisting apoptosis and DNA repair, and evading immune recognition. To tackle tumor drug resistance, many engineered drug delivery systems (DDS) have been developed. Metal-organic frameworks (MOFs) are one kind of emerging and promising nanocarriers for DDS with high surface area and abundant active sites that make the functionalization simpler and more efficient. These features enable MOFs to achieve advantages easily towards other materials. In this review, we highlight the main mechanisms of tumor drug resistance and the characteristics of MOFs. The applications and opportunities of MOF-based DDS to overcome tumor drug resistance are also discussed, shedding light on the future development of MOFs to address tumor drug resistance.

Progress in the studies on the molecular mechanisms associated with multidrug resistance in cancers

Chemotherapy is one of the important methods to treat cancer, and the emergence of multidrug resistance (MDR) is one major cause for the failure of cancer chemotherapy. Almost all anti-tumor drugs develop drug resistance over a period of time of application in cancer patients, reducing their effects on killing cancer cells. Chemoresistance can lead to a rapid recurrence of cancers and ultimately patient death. MDR may be induced by multiple mechanisms, which are associated with a complex process of multiple genes, factors, pathways, and multiple steps, and today the MDR-associated mechanisms are largely unknown. In this paper, from the aspects of protein-protein interactions, alternative splicing (AS) in pre-mRNA, non-coding RNA (ncRNA) mediation, genome mutations, variance in cell functions, and influence from the tumor microenvironment, we summarize the molecular mechanisms associated with MDR in cancers. In the end, prospects for the exploration of antitumor drugs that can reverse MDR are briefly discussed from the angle of drug systems with improved targeting properties, biocompatibility, availability, and other advantages.

Ribociclib Inhibits P-gp-Mediated Multidrug Resistance in Human Epidermoid Carcinoma Cells

The efficacy of cancer chemotherapy can be attenuated or abrogated by multidrug resistance (MDR) in cancer cells. In this study, we determined the effect of the CDK4/6 inhibitor, ribociclib (or LEE011), on P-glycoprotein (P-gp)-mediated MDR in the human epidermoid carcinoma MDR cell line, KB-C2, which is widely used for studying P-gp-mediated MDR in cancers. The incubation of KB-C2 cells with ribociclib (3–9 µM) increased the efficacy of colchicine, a substrate for P-gp. The cell expression of P-gp was down-regulated at both translation and transcription levels. Furthermore, ribociclib produced a 3.5-fold increase in the basal activity of P-gp ATPase, and the concentration required to increase basal activity by 50% (EC₅₀) was 0.04 μM. Docking studies indicated that ribociclib interacted with the drug-substrate binding site of P-gp. The short-term and long-term intracellular accumulation of doxorubicin greatly increased in the KB-C2 cells co-cultured with ribociclib, indicating ribociclib inhibited the drug efflux activity of P-gp. The results of our study indicate that LEE011 may be a potential agent for combined therapy of the cancers with P-gp mediated MDR.

Current Status and Prospects of Clinical Treatment of Osteosarcoma

Osteosarcoma, one of the common malignant tumors in the skeletal system, originates in mesenchymal tissue, and the most susceptible area of occurrence is the metaphysis with its abundant blood supply. Tumors are characterized by highly malignant spindle stromal cells that can produce bone-like tissue. Most of the osteosarcoma are primary, and a few are secondary. Osteosarcoma occurs primarily in children and adolescents undergoing vigorous bone growth and development. Most cases involve rapid tumor development and early blood metastasis. In recent years, research has grown in the areas of molecular biology, imaging medicine, biological materials, applied anatomy, surgical techniques, biomechanics, and comprehensive treatment of tumors. With developments in molecular biology and tissue bioengineering, treatment methods have also made great progress, especially in comprehensive limb salvage treatment, which significantly enhances the quality of life after surgery and improves the 5-year survival rate of patients with malignant tumors. This article provides a review of limb salvage, immunotherapy, gene therapy, and targeted therapy from traditional amputation to neoadjuvant chemotherapy, providing a reference for current clinical treatments for osteosarcoma.