Enhanced Cancer Cell Death Research Articles

Abstract 4614: Inhibition of NEK2 promotes chemosensitivity and reduces primary effusion lymphoma burden

Abstract Non-Hodgkin lymphoma (NHL) is a common cancer in both men and women, and represents a significant cancer burden worldwide. Primary effusion lymphoma (PEL) is a subtype of NHL infected with Kaposi sarcoma-associated herpesvirus (KSHV). PEL is an aggressive and lethal cancer with no current standard of care, owing largely to its propensity to develop resistance to current chemotherapeutic regimens. Here, we report a reliance of PEL on the mitotic kinase, NEK2, for survival. Genetic and pharmacologic targeting of NEK2 resulted in caspase 3-mediated apoptotic cell death of PEL. Furthermore, inhibition of NEK2 significantly prolonged survival and reduced tumor burden in a PEL mouse model. We also report that the ABC transporter proteins, MDR1 and MRP, are most active in PEL and that NEK2 inhibition of PEL reduced the expression and activity of these ABC transporter proteins, which are known to mediate drug resistance in cancer. Additionally, NEK2 inhibition sensitized both viral and non-viral NHL to other chemotherapeutic agents such as rapamycin, resulting in enhanced cancer cell death. Overall, these data offer insight into the mechanisms underlying PEL survival and drug resistance, and suggest that NEK2 is a viable therapeutic target for PEL. Citation Format: Maria C. White, Jason P. Wong, Blossom Damania. Inhibition of NEK2 promotes chemosensitivity and reduces primary effusion lymphoma burden [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 4614.

Deficiency of ligase IV leads to reduced NHEJ, accumulation of DNA damage, and can sensitize cells to cancer therapeutics

Ligase IV is a key enzyme involved during DNA double-strand breaks (DSBs) repair through nonhomologous end joining (NHEJ). However, in contrast to Ligase IV deficient mouse cells, which are embryonic lethal, Ligase IV deficient human cells, including pre-B cells, are viable. Using CRISPR-Cas9 mediated genome editing, we have generated six different LIG4 mutants in cervical cancer and normal kidney epithelial cell lines. While the LIG4 mutant cells showed a significant reduction in NHEJ, joining mediated through microhomology-mediated end joining (MMEJ) and homologous recombination (HR) were significantly high. The reduced NHEJ joining activity was restored by adding purified Ligase IV/XRCC4. Accumulation of DSBs and reduced cell viability were observed in LIG4 mutant cells. LIG4 mutant cells exhibited enhanced sensitivity towards DSB-inducing agents such as ionizing radiation (IR) and etoposide. More importantly, the LIG4 mutant of cervical cancer cells showed increased sensitivity towards FDA approved drugs such as Carboplatin, Cisplatin, Paclitaxel, Doxorubicin, and Bleomycin used for cervical cancer treatment. These drugs, in combination with IR showed enhanced cancer cell death in the background of LIG4 gene mutation. Thus, our study reveals that mutation in LIG4 results in compromised NHEJ, leading to sensitization of cervical cancer cells towards currently used cancer therapeutics.

PI3K/mTOR inhibitor VS-5584 combined with PLK1 inhibitor exhibits synergistic anti-cancer effects on non-small cell lung cancer

Small molecule drugs are of significant importance in the treatment of non-small cell lung cancer (NSCLC). Here, we explored biological effects of the PI3K/mTOR inhibitor VS-5584 on NSCLC. Our findings indicated that VS-5584 administration resulted in a dose-dependent inhibition of NSCLC cell proliferation, as well as the induction of apoptosis and cycle arrest. Additionally, we observed a significant increase in intracellular reactive oxygen species (ROS) levels following VS-5584 treatment. The use of the ROS inhibitor N-acetylcysteine (NAC) effectively reduced ROS levels and decreased the proportion of apoptotic cells. Treatment with VS-5584 led to an upregulation of genes associated with apoptosis and cell cycle, such as c-caspase 3 and P21. Conversely, a downregulation of cyclin-dependent kinase 1 (CDK1) expression was observed. Next, transcriptome analyses revealed that VS-5584 treatment altered the abundance of 1520 genes/transcripts in PC-9 cells, one of which was polo-like kinase 1 (PLK1). These differentially expressed genes were primarily enriched in biological processes such as cell cycle regulation and cell apoptosis, which are closely linked to the P53 and apoptosis pathways. Co-treatment with VS-5584 and PLK1 inhibitor NMS-P937 resulted in enhanced cancer cell death, exhibiting synergistic inhibitory activity. Notably, VS-5584 inhibited the growth of NSCLC in a patient-derived xenograft (PDX) mouse model without observable abnormalities in major organs. Overall, VS-5584 effectively suppressed the growth of NSCLC cells both in vitro and in vivo. VS-5584 combined with NMS-P937 exhibited a synergistic effect in inhibiting NSCLC cell growth. These findings suggest that VS-5584 has potential as a therapeutic strategy for treating NSCLC.

Synthesis of Pt nanoparticles with gelatin-assisted green route to improve sensitization of cancer cells to X-Ray irradiation

This study aimed to develop a novel radiosensitizer consisting of platinum nanoparticles (Pt NPs) as a high-atomic-number element in order to maximize the generation of ROS under ionizing radiation at the tumor site. Pt NPs were produced via a green and facile method in the presence of gelatin (Gel) as both reducing and stabilizing agent. After determining the physical structure and chemical composition of Pt@Gel NPs by STEM, FeSEM, EDS, DLS, XRD and FTIR, in vitro cytotoxicity on human umbilical vein endothelial cells (HUVEC) and breast cancer cell line (4T1) was evaluated by MTT assay. Finally, ROS generation assay, calcein AM/PI staining assay and clonogenic test were performed on 4T1 cells under X-Ray irradiation to evaluate the radioenhancment efficiency of Pt@Gel. The prepared NPs exhibited spherical and uniform shapes and narrowly distributed sizes in addition to an acceptable radiosensitization capability. The nanosystem provided higher levels of intracellular ROS in malignant cells and enhanced cancer cell death rate under X-Ray irradiation. Overall, the findings suggested that Pt@Gel could be a safe and effective alternative to existing radiosensitizers and potentially be employed for the treatment of breast cancer.

A Vanadium-Based Nanoplatform Synergizing Ferroptotic-like Therapy with Glucose Metabolism Intervention for Enhanced Cancer Cell Death and Antitumor Immunity.

Ferroptosis activation has been considered a mighty weapon for cancer treatment, and growing attention is being paid to reinforcing tumor cells' sensitivity to ferroptosis. However, the existence of certain ferroptosis resistance mechanisms, especially the abnormal metabolism of tumor cells, has long been underestimated. We propose an enhanced ferroptosis-activating pattern via regulating tumor cells' glycometabolism and construct a nanoplatform named PMVL, which is composed of lonidamine (LND)-loaded tannic acid coordinated vanadium oxides with the camouflage of PD-L1 inhibiting peptide-modified tumor cell membrane. This work reveals that the mixed valence of vanadium (VIV and VV) in PMVL triggers ferroptosis due to the self-cyclic valence alteration of V, the process of which generates •OH for lipid peroxide accumulation (VIV → VV) and depletes glutathione (GSH) for glutathione peroxidase (GPX4) deactivation (VV → VIV). Notably, LND strengthens ferroptosis by dual suppression of glycolysis (decreasing ATP supply) and the pentose phosphate pathway (decreasing NADPH production), causing anabatic GSH consumption. Besides, the inhibited glycolysis generates less intracellular lactic acid and alleviates the acidity of tumor microenvironment, preventing immunosuppressive M2 macrophage polarization. In vitro and in vivo data demonstrate the glycometabolism-intervention-enhanced ferroptosis and boosted immunity activation, potentially providing opportunities and possibilities for synergetic cancer therapy.

Nanostructured bioactive glasses: A bird's eye view on cancer therapy.

Bioactive glasses (BGs) arewell known for their successful applications in tissue engineering and regenerative medicine. Recent experimental studies have shown their potential usability in oncology, either alone or in combination with other biocompatible materials, such as biopolymers. Direct contact with BG particles has been found to cause toxicity and death in specific cancer cells (bone-derived neoplastic stromal cells) in vitro. Nanostructured BGs (NBGs) can be doped with anticancer elements, such as gallium, to enhance their toxic effects against tumor cells. However, the molecular mechanisms and intracellular targets for anticancer compositions of NBGs require further clarification. NBGs have been successfully evaluated for use in various well-established cancer treatment strategies, including cancer hyperthermia, phototherapy, and anticancer drug delivery. Existing results indicate that NBGs not only enhance cancer cell death, but can also participate in the regeneration of lost healthy tissues. However, the application of NBGs in oncology is still in its early stages, and numerous unanswered questions must be addressed. For example, the impact of the composition, biodegradation, size, and morphology of NBGs on their anticancer efficacy should be defined for each type of cancer and treatment strategy. Moreover, it should be more clearly assessed whether NBGs can shrink tumors, slow/stop cancer progression, or cure cancer completely. In this regard, the use of computational studies (in silico methods) is highly recommended to design the most effective glass formulations for cancer therapy approaches and to predict, to some extent, the relevant properties, efficacy, and outcomes. This article is categorized under: Implantable Materials and Surgical Technologies > Nanomaterials and Implants Implantable Materials and Surgical Technologies > Nanotechnology in Tissue Repair and Replacement Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Selective inhibition of ATM-dependent double-strand break repair and checkpoint control synergistically enhances the efficacy of ATR inhibitors.

Ataxia Telangiectasia and Rad3-Related Protein (ATR) kinase regulates a key cell regulatory node for maintaining genomic integrity by preventing replication fork collapse. ATR inhibition has been shown to increase replication stress resulting in DNA double strand breaks (DSBs) and cancer cell death, and several inhibitors are under clinical investigation for cancer therapy. However, activation of cell cycle checkpoints controlled by Ataxia Telangiectasia Mutated (ATM) kinase could minimize the lethal consequences of ATR inhibition and protect cancer cells. Here, we investigate ATR-ATM functional relationship and potential therapeutic implications. In cancer cells with functional ATM and p53 signaling, selective suppression of ATR catalytic activity by M6620 induced G1 phase arrest to prevent S-phase entry with unrepaired DSBs. The selective ATM inhibitors, M3541 and M4076, suppressed both ATM-dependent cell cycle checkpoints and DSB repair, lowered the p53 protective barrier and extended the life of ATR inhibitor induced DSBs. Combination treatment amplified the fraction of cells with structural chromosomal defects and enhanced cancer cell death. ATM inhibitor synergistically potentiated the ATR inhibitor efficacy in cancer cells in vitro and increased ATR inhibitor efficacy in vivo at doses that did not show overt toxicities. Further, a combination study in 26 patient-derived xenograft models of triple negative breast cancer with the newer generation ATR inhibitor M4344 and ATM inhibitor M4076 demonstrated substantial improvement in efficacy and survival compared to single-agent M4344, suggesting a novel and potentially broad combination approach to cancer therapy.

Abstract 6299: ZB131 antibody-drug conjugates induce potent antitumor activity

Abstract Antibody-drug conjugates (ADCs) have become increasingly adopted clinically, with 13 drugs FDA-approved and over 100 under clinical development. Despite this momentum and major advances in payload and linker technology, ADCs are limited by off-cancer target-mediated toxicities incurred by currently available targets. In contrast to genomic and proteomic strategies, our unique drug discovery approach accounts for a disease’s native context. This led to the identification of cancer-specific plectin (CSP) as not only overexpressed in malignant tissue compared to healthy, but exclusively present on the surface of cancer cells and absent in normal or pre-malignant tissue. A Phase 0 imaging trial (Biodistribution of Novel Imaging for Resectable Pancreatic Cancer - NCT01962909) evaluating a radiolabeled CSP-targeted peptide has revealed that CSP is bioavailable and abundant, with over a million CSP molecules per cancer cell in pancreatic cancer. Previously, we generated ZB131, a humanized monoclonal antibody that targets CSP. ZB131 demonstrated potent monotherapy efficacy in pancreatic, ovarian, and bile duct preclinical cancer models, indications that have high CSP expression and are being evaluated in a first-in-human Phase 1/2 clinical trial (NCT05074472). Here, we show that CSP is an ideal target for an ADC: it is abundantly and selectively expressed in many indications, bioavailable, and its inhibition is predicted to synergize with FDA-approved payloads. ZB131 binds specifically to CSP, rapidly internalizes, displays linear pharmacokinetics in pre-clinical models, and demonstrates a strong safety profile. We describe the development of two ZB131 ADCs, ZB131-MMAE (monomethyl auristatin E) and ZB131-DXd (Deruxtecan), with drug-to-antibody ratios of 3 – 4 and 7 – 8, respectively. After binding, both ADCs are rapidly and specifically internalized by CSP-positive cells resulting in drug payload release and enhancing cancer cell death compared to ZB131 alone. Moreover, we characterize cytotoxic activity in high and low CSP cell lines to evaluate ADC activity in relation to CSP abundance. In preclinical xenograft models, ZB131-ADC enhanced tumor regression compared to controls at clinically relevant doses. Furthermore, anti-huIgG staining revealed selective target engagement by ZB131-ADC. Taken together, these data show that ZB131-ADCs demonstrate potent antitumor activity and support their evaluation in a Phase 1 clinical trial. Citation Format: Samantha M. Perez, Brian P. Murphy, Danielle B. Heckert, Sarah Hall, Abby L. Colvin, Molly F. Owens, Ben R. Verfurth, Julien Dimastromatteo, Jiang He, Reid B. Adams, Yelena Kovtun, Lindsey T. Brinton, Kimberly A. Kelly. ZB131 antibody-drug conjugates induce potent antitumor activity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6299.

Docosahexaenoic Acid, a Key Compound for Enhancing Sensitization to Drug in Doxorubicin-Resistant MCF-7 Cell Line.

Drug resistance is a well-known and significant obstacle in the battle against cancer, rendering chemotherapy treatments often ineffective. To improve the effectiveness of chemotherapy, researchers are exploring the use of natural molecules that can enhance its ability to kill cancer cells and limit their spread. Docosahexaenoic acid (DHA), a lipid found in marine fish, has been shown to enhance the cytotoxicity of various anti-cancer drugs in vitro and in vivo. While the combined use of chemotherapeutic drugs with DHA demonstrated promising preliminary results in clinical trials, there is still a significant amount of information to be discovered regarding the precise mechanism of action of DHA. As the biological pathways involved in the chemosensitization of already chemoresistant MCF-7 cells are still not entirely unraveled, in this study, we aimed to investigate whether DHA co-treatment could enhance the ability of the chemotherapy drug doxorubicin to inhibit the growth and invasion of MCF-7 breast cancer cells (MCF-7/Dox) that had become resistant to the drug. Upon treating MCF-7/Dox cells with DHA or DHA-doxorubicin, it was observed that the DHA-doxorubicin combination effectively enhanced cancer cell death by impeding in vitro propagation and invasive ability. In addition, it led to an increase in doxorubicin accumulation and triggered apoptosis by arresting the cell cycle at the G2/M phase. Other observed effects included a decrease in the multi-drug resistance (MDR) carrier P-glycoprotein (P-gp) and TG2, a tumor survival factor. Augmented quantities of molecules promoting apoptosis such as Bak1 and caspase-3 and enhanced lipid peroxidation were also detected. Our findings in the cell model suggest that DHA can be further investigated as a natural compound to be used alongside doxorubicin in the treatment of breast cancer that is unresponsive to chemotherapy.

Preparation of alginate coated Pt nanoparticle for radiosensitization of breast cancer tumor

Noble metals as high atomic number elements can localize X-ray radiation within tumor cells by exploiting different mechanisms. Here, alginate (Alg)-coated platinum nanoparticles (Pt@Alg) were synthesized, characterized, and implemented as a radiosensitizer to enhance X-ray therapeutic efficacy in breast cancer in vitro and in vivo. Alg not only improves the biocompatibility of the radioenhancer, but also stabilizes the nanoparticles. Pt@Alg was studied by different characterization methods including DLS, STEM, Fe-SEM, XRD, XPS, FT-IR and UV–Vis spectrophotometry. The nanosystem provided a higher level of intracellular ROS in malignant cells and enhanced cancer cell death under X-Ray irradiation. Clonogenic assay also demonstrated the radiosensitizing properties of the nanosystem, in vitro. In vivo result show tumor growth restraining properties of the nanosystem when it was administrated along with X-Ray irradiation. Histopathology results confirmed the impact of nanosystem and X-ray co-treatment, as well. Altogether, the importance of radiosensitizers for improving radiotherapy outcomes was highlighted.

Terminalia chebula Polyphenol and Near-Infrared Dye-Loaded Poly(lactic acid) Nanoparticles for Imaging and Photothermal Therapy of Cancer Cells.

Photothermal/photodynamic therapies (PTT/PDT) are multimodal approaches employing near-infrared (NIR) light-responsive photosensitizers for cancer treatment. In the current study, IR-775, a hydrophobic photosensitizer, was used in combination with a polyphenols (p)-rich ethyl acetate extract from Terminalia chebula to treat cancer. IR-775 dye and polyphenols were encapsulated in a poly(lactic acid) polymeric nanosystem (PpIR NPs) to increase the cell bioavailability. The hydrodynamic diameter of PpIR NPs is 142.6 ± 2 nm and exhibited physical stability. The nanosystem showed enhanced cellular uptake in a lung cancer cell line (A549). Cell cytotoxicity results indicate that PpIR NPs showed more than 82.46 ± 3% cell death upon NIR light treatment compared to the control groups. Both PDT and PTT generate reactive oxygen species (ROS) and cause hyperthermia, thereby enhancing cancer cell death. Qualitative and quantitative analyses have depicted that PpIR NPs with NIR light irradiation have decreased protein expression of HSP70 and PARP, and increased γ-H2AX, which collectively lead to cell death. After NIR light irradiation, the relative gene expression patterns of HSP70 and CDK2Na were also downregulated. Further, PpIR NPs uptake has been studied in 3D cells and in ovo bioimaging in zebrafish models. In conclusion, the PpIR NPs show good cancer cell cytotoxicity and present a potential nanosystem for bioimaging.

Ablative Dose Radiation Induces Distinct Waves of Cell Death Dependent on Cell Cycle Phase via DNA Repair Pathway Choice

<h3>Purpose/Objective(s)</h3> Ablative Intensity Radiotherapy (ART; also called stereotactic ablative radiotherapy) enables treatment in a limited number of high-dose radiation fractions. ART leads to unprecedented cure rates, thought to be driven in part through immune responses. However, the mechanism(s) of ART-induced cancer cell death remain poorly characterized. We hypothesized that ART induces distinct mechanisms of cell death which drive tumor immunogenicity. <h3>Materials/Methods</h3> A range of cell lines including immortalized normal and cancer cell lines were subjected to single fraction doses of radiotherapy ranging from 2-20Gy <i>in vitro</i>. Outcomes were measured using clonogenic assays, long-duration live cell imaging, and biochemical assays. The Fluorescence Ubiquitin Cell Cycle Indicator system was used to monitor phase of the cell cycle during irradiation. Key DNA repair pathways were inhibited using genetic and/or pharmacological inhibition. <h3>Results</h3> Single doses of >=8Gy (hereafter ‘ART') induce a characteristic shift in timing and mechanism of cell death. As expected, ART induces senescence in cells with intact TP53. ART induces two distinct waves of cancer cell death in cells with inactive TP53. The first wave of death occurs exclusively during mitosis in cells irradiated in the S/G2 cell cycle phases. Mitotic death is signaled via BAX/BAK-dependent intrinsic apoptosis and driven by WAPL-dependent cohesion fatigue. The second cell death wave occurs days after ART, specifically within the cells that were irradiated in G1 phase. This latter cell death wave follows at least one cell division with chromosome segregation errors and is contemporaneous with a proinflammatory response, autophagy, and STAT-1 dependent extrinsic apoptosis. Strikingly, this cell-cycle dependence is absent with doses of 2-4Gy RT. Altering DNA repair pathways changes the spectrum of cell death outcomes. Specifically, inhibiting non-homologous end joining (NHEJ) promotes mitotic catastrophe of G1 phase irradiated cells; inhibiting canonical homology directed repair reduces the amount of mitotic death in S/G2 irradiated cells; and inhibiting single strand annealing significantly delays entry into mitotic catastrophe while increasing lethality. <h3>Conclusion</h3> ART lethality results from distinct mechanisms governed by cell cycle-dependent DNA repair pathways active at the time of irradiation. Our data suggest that NHEJ promotes immune activation and ‘toxic' HR drives mitotic catastrophe. Further, mode of ART lethality is tuneable through pharmacological manipulation, indicating the potential to enhance cancer cell death and potentiate immunotherapy effectiveness for patient benefit.

Novel substituted isoindolinones derived from lawsone: synthesis, characterization, theoretical, biological activity and docking studies

An efficient Mannich type multicomponent reaction approach was developed for the synthesis of a series of novel substituted isoindolinones derived from Lawsone, 2-formyl benzoic acid, and various primary amines. This protocol features direct construction of C-N and C-C bonds via metal-free method at room temperature using an environment-friendly solvent. The synthesized isoindolinone compounds 4a-4m were characterized by various spectroscopic techniques such as 1H NMR, 13C NMR, FT-IR, and ESI-MS. Computational studies were carried out by the DFT method using B3LYP/6-31G (d,p) basic set as a tool to analyse the chemical reactivity parameters and comprehend the molecular interaction. The molecular electrostatic potential (MEP), dipole moment, chemical reactivity, and stability features of investigated isoindolinones revealed that 4i, 4j, 4l, and 4m could be promising candidates for further biological activity. The cytotoxic activity of selected compounds was evaluated using MTT assay against HepG2 cell lines (Human liver cancer cell line). The data revealed that screened compounds displayed excellent to moderate activity. The docking examination was executed on a promising liver cancer-associated Alpha fetoprotein (AFP). It showed a positive outcome with minimum binding energy and hydrogen bond interaction. Furthermore, In vivo studies ascertained that synthesized isoindolinone derivatives can lead to enhanced cancer cell death and prevention of tumor growth by restoring serum SGOT and SGPT levels near to normal. It further restores matrix metallopeptidase (MMP-2 and MMP-9 levels) near to control confirms the effectiveness of the compound.

Anticancer Cytotoxic Activity of Bispidine Derivatives Associated with the Increasing Catabolism of Polyamines.

Polyamine (PA) catabolism is often reduced in cancer cells. The activation of this metabolic pathway produces cytotoxic substances that might cause apoptosis in cancer cells. Chemical compounds able to restore the level of PA catabolism in tumors could become potential antineoplastic agents. The search for activators of PA catabolism among bicyclononan-9-ones is a promising strategy for drug development. The aim of the study was to evaluate the biological activity of new 3,7-diazabicyclo[3.3.1]nonan-9-one derivatives that have antiproliferative properties by accelerating PA catabolism. Eight bispidine derivatives were synthetized and demonstrated the ability to activate PA catabolism in regenerating rat liver homogenates. However, only three of them demonstrated a potent ability to decrease the viability of cancer cells in the MTT assay. Compounds 4c and 4e could induce apoptosis more effectively in cancer HepG2 cells rather than in normal WI-38 fibroblasts. The lead compound 4e could significantly enhance cancer cell death, but not the death of normal cells if PAs were added to the cell culture media. Thus, the bispidine derivative 4e 3-(3-methoxypropyl)-7-[3-(1H-piperazin-1-yl)ethyl]-3,7-diazabicyclo[3.3.1]nonane could become a potential anticancer drug substance whose mechanism relies on the induction of PA catabolism in cancer cells.

Metal-phenolic networks-encapsulated cascade amplification delivery nanoparticles overcoming cancer drug resistance via combined starvation/chemodynamic/chemo therapy

Multidrug resistance (MDR) of cancer is the main reason for cancer chemotherapy failure, and the use of anticancer drugs usually brings about adverse side effects to patients. Therefore, the aim of developing new cancer treatments must consider overcoming MDR and abating the toxicity of drugs to normal tissues. In this work, we designed and prepared multifunctional cascade amplification delivery nanoparticles (CADNs) with a core structure composed of glucose oxidase (GOx)-attached Fe3O4 nanoparticles, and a shell layer of PEGylated metal-phenolic networks (MPNs), in which the prodrug of doxorubicin (pDOX) was loaded. In vitro assays showed that the MPNs had dual sensitivities to acidic and reducing conditions, and the CADNs promoted the production of hydroxyl radicals in the presence of H2O2 and glucose. Besides, cellular experiments demonstrated that CADNs could efficiently facilitate the accumulation of pDOX in doxorubicin-resistant MCF-7/Adr cells and enhance cancer cell death under the combined action of ferroptosis and chemotherapy. Furthermore, in vivo assays also showed that CADNs with a PEGylated surface could effectively target tumors, and dramatically suppress the growth of both MCF-7 and MCF-7/Adr tumors, with excellent biosafety. This work presents a novel strategy for overcoming cancer MDR by driving cascade reactions to achieve starvation/chemodynamic/chemo combination therapy.

Phase Ib study of avelumab and taxane based chemotherapy in platinum-refractory or ineligible metastatic urothelial cancer (AVETAX study).

503 Background: Metastatic urothelial cancer is aggressive and associated with dismal 5-yr overall survival. Platinum-based chemotherapy and checkpoint inhibitors are standard first-line options with enfortumab vedotin, sacituzumab govitecan, and erdafitinib (in select FGFR altered tumors) subsequently utilized upon disease progression. However, despite these options, long-term outcomes remain poor, and novel strategies are needed to improve oncologic outcomes. We hypothesized that combining avelumab (anti-PD-L1 immunotherapy) with docetaxel is safe and will enhance cancer cell death by releasing neoantigens and potentiating anti-tumor immune-mediated cytotoxicity. Methods: This is a phase 1b, single-arm, open-label prospective clinical trial evaluating the combination of avelumab with docetaxel in adult subjects with locally advanced or metastatic urothelial carcinoma with disease progression during or following platinum-containing chemotherapy or within 12 months of neoadjuvant or adjuvant platinum-containing chemotherapy. There are two phases. In Phase 1b, dose de-escalation of docetaxel (Level 0: 75, Level -1: 60 or Level -2: 45 mg/m2) with standard dose avelumab (10 mg/kg) aimed to establish the phase 2 dose in a standard 3+3 design. In dose-expansion, avelumab with the RP2D of docetaxel was evaluated for efficacy. The combination therapy is administered every 3 weeks for 6 cycles, and then avelumab alone is continued every 2 weeks. The primary endpoint is safety. Efficacy endpoints include objective response rate (ORR), progression-free survival (PFS) and overall survival (OS). Results: At the cutoff date of 10/8/2021, 21 patients were enrolled in the study. Only one of the 6 patients treated with level 0 dose of docetaxel had dose-limiting toxicity (neutropenic fever). Docetaxel at 75 mg/m2 along the avelumab was deemed safe for dose expansion cohort. An additional 15 patients were enrolled in the dose-expansion cohort. Of the 20 evaluable patients, ORR (CR+PR) was seen in 70% of subjects. (CR: 30%, PR: 40%, SD: 5%, PD: 25%, and 1 patient was not evaluable). The median PFS was 9.2 months (range: 1.5 – 25.8 months), and median OS was not reached. The most common Grade 3 or 4 AEs were febrile neutropenia, transaminitis, diarrhea, anemia, and neutropenia. No treatment-related deaths were noted. Conclusions: The combination of avelumab with docetaxel is safe with promising efficacy that is worth further studying in patients with platinum-refractory or ineligible metastatic urothelial cancer. Clinical trial information: NCT03575013.

GSH facilitates the binding and inhibitory activity of novel multidrug resistance protein 1 (MRP1) modulators.

MRP1 (ABCC1) is a membrane transporter that confers multidrug resistance in cancer cells by exporting chemotherapeutic agents, often in a reduced glutathione (GSH)-dependent manner. This transport activity can be altered by compounds (modulators) that block drug transport while simultaneously stimulating GSH efflux by MRP1. In MRP1-expressing cells, modulator-stimulated GSH efflux can be sufficient to deplete GSH and increase sensitivity to chemotherapy, enhancing cancer cell death. Further development of clinically useful MRP1 modulators requires a better mechanistic understanding of modulator binding and its relationship to GSH binding and transport. Here, we explore the mechanism of two MRP1 small molecule modulators, 5681014 and 7914321, in relation to a bipartite substrate-binding cavity of MRP1. Binding of these modulators to MRP1 was dependent on the presence of GSH but not its reducing capacity. Accordingly, the modulators poorly inhibited organic anion transport by K332L-mutant MRP1, where GSH binding and transport is limited. However, the inhibitory activity of the modulators was also diminished by mutations that limit E2 17βG but spare GSH-conjugate binding and transport (W553A, M1093A, W1246A), suggesting overlap between the E2 17βG and modulator binding sites. Immunoblots of limited trypsin digests of MRP1 suggest that binding of GSH, but not the modulators, induces a conformation change in MRP1. Together, these findings support the model, in which GSH binding induces a conformation change that facilitates binding of MRP1 modulators, possibly in a proposed hydrophobic binding pocket of MRP1. This study may facilitate the structure-guided design of more potent and selective MRP1 modulators.

A multifunctional nanoamplifier with self-enhanced acidity and hypoxia relief for combined photothermal/photodynamic/starvation therapy

Phototherapies, including photothermal therapy (PTT) and photodynamic therapy (PDT) have been potential noninvasive therapeutic modality with high efficiency, however, there still exist some intrinsic limitations that impede their clinical applications. Herein, taking the advantages of the synergistic effect and high reactivity of manganese dioxide (MnO2) nanosheets and glucose oxidase (GOx), multifunctional MPDA@MnO2-MB-GOx nanoamplifier was constructed for enhanced PTT, PDT, and starvation therapy. In tumor microenvironment (TME), MnO2 nanosheets on the surface of mesoporous polydopamine (MPDA) could react with endogenous hydrogen peroxide (H2O2) and generate oxygen (O2) to relieve tumor hypoxia, thus enhancing the efficacy of PDT and GOx catalysis. Glucose consumption under the catalysis of GOx will enhance the acidity of TME and increase intracellular H2O2 concentration, which in turn promotes the production of O2 by MnO2 nanosheets, thus forming efficient cascade reaction and maximizing the efficacy of the functional agents. Furthermore, the heat generated by MPDA under the irradiation of 808 nm laser can accelerate chemical reactions, thus further enhancing synergistic therapeutic efficacy. In vitro/vivo results emphasize that enhanced cancer cell death and tumor inhibition are gained by modulating unfavorable TME with the functional nanosystem, which highlights the promise of the synthesized MPDA@MnO2-MB-GOx nanomaterial to overcome the limitations of phototherapy.

Inhibition of BMI-1 Induces Apoptosis through Downregulation of DUB3-Mediated Mcl-1 Stabilization

BMI-1, a polycomb ring finger oncogene, is highly expressed in multiple cancer cells and is involved in cancer cell proliferation, invasion, and apoptosis. BMI-1 represents a cancer stemness marker that is associated with the regulation of stem cell self-renewal. In this study, pharmacological inhibition (PTC596) or knockdown (siRNA) of BMI-1 reduced cancer stem-like cells and enhanced cancer cell death. Mechanistically, the inhibition of BMI-1 induced the downregulation of Mcl-1 protein, but not Mcl-1 mRNA. PTC596 downregulated Mcl-1 protein expression at the post-translational level through the proteasome-ubiquitin system. PTC596 and BMI-1 siRNA induced downregulation of DUB3 deubiquitinase, which was strongly linked to Mcl-1 destabilization. Furthermore, overexpression of Mcl-1 or DUB3 inhibited apoptosis by PTC596. Taken together, our findings reveal that the inhibition of BMI-1 induces Mcl-1 destabilization through downregulation of DUB3, resulting in the induction of cancer cell death.

Salubrinal Enhances Cancer Cell Death during Glucose Deprivation through the Upregulation of xCT and Mitochondrial Oxidative Stress.

Cancer cells have the metabolic flexibility to adapt to heterogeneous tumor microenvironments. The integrated stress response (ISR) regulates the cellular adaptation response during nutrient stress. However, the issue of how the ISR regulates metabolic flexibility is still poorly understood. In this study, we activated the ISR using salubrinal in cancer cells and found that salubrinal repressed cell growth, colony formation, and migration but did not induce cell death in a glucose-containing condition. Under a glucose-deprivation condition, salubrinal induced cell death and increased the levels of mitochondrial reactive oxygen species (ROS). We found that these effects of salubrinal and glucose deprivation were associated with the upregulation of xCT (SLC7A11), which functions as an antiporter of cystine and glutamate and maintains the level of glutathione to maintain redox homeostasis. The upregulation of xCT did not protect cells from oxidative stress-mediated cell death but promoted it during glucose deprivation. In addition, the supplementation of ROS scavenger N-acetylcysteine and the maintenance of intracellular levels of amino acids via sulfasalazine (xCT inhibitor) or dimethyl-α-ketoglutarate decreased the levels of mitochondrial ROS and protected cells from death. Our results suggested that salubrinal enhances cancer cell death during glucose deprivation through the upregulation of xCT and mitochondrial oxidative stress.