Plasma Membrane Of Cancer Cells Research Articles

Phosphatidylserine-targeting bis(zinc-dipicolylamine) farnesol inhibits ATP production in cancer cells to overcome multidrug resistance

Multidrug resistance significantly impedes the efficacy of cancer chemotherapy. Resistance often arises from the reduced cellular uptake of chemotherapeutic drugs, a process crucial for their cytotoxic effects. This reduction is frequently due to transmembrane efflux pumps powered by ATP from mitochondria and the cytoplasmic matrix, leading to lower intracellular concentrations of these drugs. This study introduces an amphiphilic molecule, bis(zinc-dipicolylamine) farnesol (Bis-ZnDPA), which targets phosphatidylserine (PS) – a negatively charged phospholipid prominently displayed on the outer leaflet of cancer cell plasma membranes. Integrating the hydrophobic segment of Bis-ZnDPA into the plasma membrane disrupts its integrity, potentially leading to hole formation and facilitating the uptake of chemotherapeutic drugs. Furthermore, the binding of Bis-ZnDPA to phosphatidylserine inhibits ATP production caused by Ca2+ influx and deregulation of the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) signaling pathway, reducing the efflux of drugs from cells. The results indicate the potent synergistic effect of Bis-ZnDPA with chemotherapeutic agents, suggesting that targeting PS is a viable strategy for overcoming multidrug resistance in cancer chemotherapy.

Abstract 6348: Unveiling diverse trimeric forms of STEAP1 in human prostate cancer cells: Exploring STEAP1-STEAP2 interdependence for expression and plasma membrane localization

Abstract Six-Transmembrane Epithelial Antigen of the Prostate 1 (STEAP1) is an emerging therapeutic target that is a member of the STEAP1-4 family of metalloreductases. We recently reported the preclinical characterization of xaluritamig (AMG 509), a STEAP1 XmAb® 2+1 T-cell engager molecule that is being developed for the treatment of prostate cancer (Nolan-Stevaux et al, 2023). Xaluritamig is designed to preferentially target tumor cells that express high levels of STEAP1. However, prostate tumor cells also express high levels of STEAP2. Here, we characterize the interactions between STEAP1 and STEAP2 in prostate cancer cell lines and the impact to xaluritamig activity. Bulk mRNA as well as single-cell gene expression data (scRNAseq) reveal a strong correlation between STEAP1 and STEAP2 expression in human prostate cancer, suggesting that the STEAP proteins may form both homotrimers and heterotrimers in prostate tumors. To test this idea, we investigated the structural behavior of STEAP1/2 trimers in human prostate cancer cell lines that endogenously express STEAP1 and STEAP2. Using xaluritamig and the parental anti-STEAP1 antibody, we show that STEAP1 primarily forms heterotrimers with STEAP2 in prostate cancer cells but can also assemble as homotrimers in the absence of STEAP2. Both STEAP1/2 heterotrimers and STEAP1 homotrimers can be targeted by xaluritamig, leading to T cell-dependent cellular cytotoxicity. Similarly, we found that anti-STEAP2 antibodies detected STEAP2 homotrimers when STEAP1 expression was ablated in cells, and that both STEAP1/2 heterotrimers and STEAP2 homotrimers were targeted by a STEAP2-specific T-cell engager molecule. We also demonstrate that neither STEAP1 nor STEAP2 significantly influences the mRNA or protein expression of the other. Our data elucidates the versatility of STEAP family members in forming both homotrimers and heterotrimers on the plasma membrane of human prostate cancer cells and the potential for therapeutic targeting with STEAP1/2-directed therapies. Characterizing the capability of existing STEAP1 or STEAP2 targeting therapeutics to bind their respective targets, whether within a homotrimer or heterotrimer, is crucial for a comprehensive understanding of the therapeutic potential of these drugs. Further research will help delineate the mechanism underlying the formation of STEAP1/2 trimers in cancer cells and continue advancing our understanding of this intriguing biological relationship. Citation Format: Cong Li, Lingming Liang, Joonhee Park, Olga Pryshchep, Binnaz Staley, Peng Li, Ben Alba, Xuan Liu, Fei Li, Gregory L. Moore, Matthew J. Bernett, Umesh Muchhal, John Desjarlais, Angela Coxon, Julie M. Bailis. Unveiling diverse trimeric forms of STEAP1 in human prostate cancer cells: Exploring STEAP1-STEAP2 interdependence for expression and plasma membrane localization [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 6348.

Membrane Partitioning of TEMPO Discriminates Human Lung Cancer from Neighboring Normal Cells.

The plasma membranes of normal and cancer cells of the lung, breast, and colon tissues show considerably different lipid compositions that greatly influence their physicochemical properties. Partitioning of the spin probe 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) into the membranes of human lung normal and carcinoma cells was assessed by EPR spectroscopy to estimate the impact of the lipid compositions. The goal was to reveal potential strategies for cancer therapy attributable to the membrane properties. The study was conducted at pH values of 7.3 and 6.2, relevant to the microenvironments of normal and cancer cells, respectively. The TEMPO partitioning was examined in the temperature interval of 283-317K to reveal the efficacy of local hyperthermia used in chemotherapy. Results indicate that the TEMPO partitioning coefficient for the membranes of human lung carcinoma cells is significantly higher compared with that of neighboring normal cells. Increased partition coefficients were observed at relatively higher temperatures in both normal and cancer cells. However, compared to the normal cells, the cancer cells demonstrated higher partition coefficients in the studied temperature range. The data obtained with C12SL (spin-labeled analog of lauric acid) indicate that increased membrane dynamics of the cancer cells is a possible mechanism for enhanced partitioning of TEMPO. Free energy values for partitioning estimated for pH values of 6.2 and 7.3 show that TEMPO partitioning requires 30% less energy in the cancer cells at pH 7.3. TEMPO and its derivatives have previously been considered as theranostic agents in cancer research. Data suggest that TEMPO derivatives could be used to test if complementary alkalization therapy is effective for cancer patients receiving standard chemotherapy with local hyperthermia.

Bionic nanotheranostic for multimodal imaging-guided NIR-II-photothermal cancer therapy.

In photothermal therapy (PTT), the photothermal conversion of the second near-infrared (NIR-II) window allows deeper penetration and higher laser irradiance and is considered a promising therapeutic strategy for deep tissues. Since cancer remains a leading cause of deaths worldwide, despite the numerous treatment options, we aimed to develop an improved bionic nanotheranostic for combined imaging and photothermal cancer therapy. We combined a gold nanobipyramid (Au NBP) as a photothermal agent and MnO2 as a magnetic resonance enhancer to produce core/shell structures (Au@MnO2; AM) and modified their surfaces with homologous cancer cell plasma membranes (PM) to enable tumour targeting. The performance of the resulting Au@MnO2@PM (AMP) nanotheranostic was evaluated in vitro and in vivo. AMP exhibits photothermal properties under NIR-II laser irradiation and has multimodal in vitro imaging functions. AMP enables the computed tomography (CT), photothermal imaging (PTI), and magnetic resonance imaging (MRI) of tumours. In particular, AMP exhibited a remarkable PTT effect on cancer cells in vitro and inhibited tumour cell growth under 1064 nm laser irradiation in vivo, with no significant systemic toxicity. This study achieved tumour therapy guided by multimodal imaging, thereby demonstrating a novel strategy for the use of bionic gold nanoparticles for tumour PTT under NIR-II laser irradiation.

Molecular Engineering of Plasma Membrane and Mitochondria Dual-Targeted NIR-II AIE Photosensitizer Evoking Synergetic Pyroptosis and Apoptosis.

Phototherapy provides a noninvasive and spatiotemporal controllable paradigm to inhibit the evasion of the programmed cell death (PCD) of tumors. However, conventional photosensitizers (PSs) often induce a single PCD process, resulting in insufficient photodamage and severely impeding their application scopes. In this study, molecular engineering is conducted by adjusting electron donors to develop an aggregation-induced NIR-II emissive PS (DPITQ) for plasma membrane and mitochondria dual-targeted tumor therapy by evoking synergetic pyroptosis and apoptosis. DPITQ displays boosted type I and II reactive oxygen species generation as well as a high photothermal conversion efficacy (43%) after laser irradiation of 635 nm. The excellent biocompatibility and appropriate lipophilicity help the DPITQ to specifically anchor in the plasma membrane and mitochondria of cancer cells. Furthermore, the photosensitized DPITQ can disrupt the intact plasma membrane and cause mitochondrial dysfunction, ultimately causing concurrent pyroptosis and apoptosis to suppress cancer cell proliferation even under hypoxia. It is noteworthy that the DPITQ nanoparticles (NPs) present clear NIR-II fluorescence imaging capability on the venous vessels of nude mice. Notably, the DPITQ NPs exert efficient NIR-II fluorescence imaging-guided phototherapy both in multicellular tumor spheroids and in vivo, causing maximum destruction to tumors but minimum adverse effects to normal tissue.

A mechanosensitive caveolae–invadosome interplay drives matrix remodelling for cancer cell invasion

Invadosomes and caveolae are mechanosensitive structures that are implicated in metastasis. Here, we describe a unique juxtaposition of caveola clusters and matrix degradative invadosomes at contact sites between the plasma membrane of cancer cells and constricting fibrils both in 2D and 3D type I collagen matrix environments. Preferential association between caveolae and straight segments of the fibrils, and between invadosomes and bent segments of the fibrils, was observed along with matrix remodelling. Caveola recruitment precedes and is required for invadosome formation and activity. Reciprocally, invadosome disruption results in the accumulation of fibril-associated caveolae. Moreover, caveolae and the collagen receptor β1 integrin co-localize at contact sites with the fibrils, and integrins control caveola recruitment to fibrils. In turn, caveolae mediate the clearance of β1 integrin and collagen uptake in an invadosome-dependent and collagen-cleavage-dependent mechanism. Our data reveal a reciprocal interplay between caveolae and invadosomes that coordinates adhesion to and proteolytic remodelling of confining fibrils to support tumour cell dissemination.

65P Transmembrane distribution of phosphatidylethanolamine in plasma membrane of ovarian cancer cells under conditions mimicking tumor microenvironment

65P Transmembrane distribution of phosphatidylethanolamine in plasma membrane of ovarian cancer cells under conditions mimicking tumor microenvironment

Structure-activity relationship studies and biological properties evaluation of peptidic NRP-1 ligands: Investigation of N-terminal cysteine importance

Neuropilin-1 (NRP-1) is a major co-receptor of vascular endothelial growth factor receptor-2 (VEGFR-2). It may also stimulate tumour growth and metastasis independently of VEGF-A165. These functions make VEGF-A165/NRP-1 complex formation and its inhibition of great interest, where NRP-1 is the target for which effective ligands are sought. Design of peptide-like inhibitors represent a strategy with great potential in the treatment of NRP-1-related disorders. Here, we present the synthesis, molecular modelling, structure-activity relationship studies as well as biological evaluation of peptides with the branched sequences H2N-X-Lys(hArg)-Dab-Oic-Arg-OH and H2N-Lys(X-hArg)-Dab-Oic-Arg-OH. Two of the designed peptides, in which Cys was inserted in X position, expressed high affinity (∼40 nM value) for NRP-1 and were resistant to enzymatic digestion in human serum. Moreover, peptide/NRP-1 complex promoted fast intracytoplasmic protein trafficking towards the plasma membrane in breast cancer cells. Our results suggest that these compounds might be good candidates for further development of VEGF-A165/NRP-1 inhibitors.

Role of organic cation transporter 3 (OCT3) in the response of hepatocellular carcinoma to tyrosine kinase inhibitors

Impaired function of organic cation transporter 1 (OCT1) in hepatocellular carcinoma (HCC) has been associated with unsatisfactory response to sorafenib. However, some patients lacking OCT1 at the plasma membrane (PM) of HCC cells still respond to sorafenib, suggesting that another transporter may contribute to take up this drug. The aim of this study was to investigate whether OCT3 could contribute to the uptake of sorafenib and other tyrosine kinase inhibitors (TKIs) and whether OCT3 determination can predict HCC response to sorafenib. Cells overexpressing OCT3 were used to determine the ability of this carrier to transport sorafenib. Immunostaining of OCT3 was performed in HCC samples obtained in the TRANSFER study. Considering the intensity of staining and the number of OCT3-positive cells, tumors were classified as having absent, weak, moderate, or strong OCT3 expression and were also categorized according to the presence or absence of PM staining. Functional in vitro studies revealed that OCT3 is also able to mediate sorafenib uptake. Other TKIs, such as regorafenib, lenvatinib, and cabozantinib can also interact with this transporter. In silico studies suggested that the expression of OCT3 is better preserved in HCC than that of OCT1. In HCC samples, OCT3 was expressed at the PM of cancer cells, and its presence, detected in 26% of tumors, was associated with better outcomes in patients treated with sorafenib. In conclusion, analysis by immunohistochemistry of OCT3 in the PM of tumor cells may help to predict the response of HCC patients to sorafenib and potentially to other TKIs.

Surface‐enhanced Raman imaging of intact cancer cell membrane on a rough aluminum substrate

AbstractThe plasma membrane of cancer cells displays differences in lipid and protein composition which distinguish them from healthy cells. Certain molecules have such prominent vibrational characteristics that they can be considered cancer biomarkers. Although Raman spectroscopy is a label‐free non‐invasive method of chemical analysis, it, however, has been limited by weak signals from the membrane compared to the bulk interior of cells. Surface‐enhanced Raman scattering (SERS) on plasmonic gold and silver substrates has previously been used to overcome this limitation. However, the high cost, poor repeatability, and toxicity of these noble metals hinder their practical applications. These challenges may be solved by using different materials and nanostructures. Here, we performed SERS imaging of ovarian cancer cells on rough aluminum substrates and extracted the Raman signals of intact cell membranes by comparing these with the corresponding measurements on Si substrates. We used atomic force microscopy (AFM) for Raman signal calibration. The comparison of cancer and normal cell membranes revealed the different lipid/protein peak ratios in cytoplasm and nucleus‐proximal areas. These Raman signatures of the ovarian cancer can be used as new biomarkers. This method may be extended to other types of cancer biosensing based on aluminum plasmonics.

In vivo imaging of acute physiological responses after treatment of cancer with near-infrared photoimmunotherapy.

Near-infrared photoimmunotherapy (NIR-PIT) is a new cancer phototherapy using an antibody-photosensitizer conjugate (Ab-IR700). By NIR light irradiation, Ab-IR700 forms a water-insoluble aggregation on the plasma membrane of cancer cells, leading to lethal membrane damage of cancer cells with high selectivity. However, IR700 produces singlet oxygen, which induces non-selective inflammatory responses such as edema in normal tissues around the tumor. Understanding such treatment-emergent responses is important to minimize side effects and improve clinical outcomes. Thus, in this study, we evaluated physiological responses during NIR-PIT by magnetic resonance imaging (MRI) and positron emission tomography (PET). Ab-IR700 was intravenously injected into tumor-bearing mice with two tumors on the right and left sides of the dorsum. At 24h after injection, a tumor was irradiated with NIR light. Edema formation was examined by T1/T2/diffusion-weighted MRI and inflammation was investigated by PET with 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). Because inflammation can increase vascular permeability via inflammatory mediators, we evaluated changes in oxygen levels in tumors using a hypoxia imaging probe, [18F]fluoromisonidazole ([18F]FMISO). The uptake of [18F]FDG in the irradiated tumor was significantly decreased compared to the control tumor, indicating the impairment of glucose metabolism induced by NIR-PIT. MRI and [18F]FDG-PET images showed that inflammatory edema with [18F]FDG accumulation was present in the surrounding normal tissues of the irradiated tumor. Furthermore, [18F]FMISO accumulation in the center of the irradiated tumor was relatively low, indicating the enhancement of oxygen supply due to increased vascular permeability. In contrast, high [18F]FMISO accumulation was observed in the peripheral region, indicating enhancement of hypoxia in the region. This could be because inflammatory edema was formed in the surrounding normal tissues, which blocked blood flow to the tumor. We successfully monitored inflammatory edema and changes in oxygen levels during NIR-PIT. Our findings on the acute physiological responses after light irradiation will help to develop effective measures to minimize the side effects in NIR-PIT.

Selective Visualization of Tumor Cell Membranes and Tumors with a Viscosity-Sensitive Plasma Membrane Probe.

Cancer is a worldwide health problem. Revealing the changes in the microenvironment after cell carcinogenesis is helpful to understand cancer and develop sensitive methods for cancer diagnosis. We developed herein a viscosity-responsive plasma membrane probe (TPA-S) that was successfully used to probe the viscosity difference between normal and tumor cell plasma membranes for the first time. The probe shows AIE properties with good water solubility, significant near-infrared (NIR) fluorescence responses to viscosity with high sensitivity, and excellent cell membrane location performance. With these features, our experiments showed that TPA-S could selectively visualize cancer cell plasma membranes, revealing that the plasma membrane of tumor cells is more viscous than that of normal cells. In addition, TPA-S was successfully applied to specifically light up tumors. Altogether, this work explored the changes of cell membrane viscosity after canceration, provided a new method for selective visualization of tumor cells, and opened up a new approach for cancer diagnosis.

Phytogalactolipids activate humoral immunity against colorectal cancer

BackgroundColorectal cancer (CRC) is the third most lethal cancer in the world, and its incidence is steadily rising. In this study, we investigated the induction of humoral immunity by a phytogalactolipid enriched fraction (CRA) derived from the medicinal plant Crassocephalum rabens (Benth.) S. Moore to combat CRC.MethodsImmunocompetent BALB/c mice were used to evaluate CRA's therapeutic effects in CRC. The phenotypes of B cell subsets in splenocytes and tumors from the CRA-treated mice were isolated and analyzed by flow cytometry. The titers, isotypes, specificity, antigen recognition, and cytotoxic activity of CRA-induced anti-tumor antibodies were determined. The mechanisms of CRA on B cell differentiation were determined by cell-based analyses, including co-cultural with T cells, cytokine analysis, gene expression by qPCR, and protein expression by western blotting.ResultsCRA efficiently inhibited tumor growth in colorectal tumor-bearing allograft mice. CRA treatment attracted an abundance of B cells into the tumor consequently enhancing the anti-tumor antibodies in sera and inducing a class-switch. CRA-induced antisera (designated CRA antisera) specifically recognized surface antigens on the plasma membrane of cancer cells. CRA antisera induced cytotoxicity including antibody-dependent cell cytotoxicity, phagocytosis, and complement-dependent cytotoxicity. CRA interacted with IL-6 receptor to activate STAT3 and cMaf, resulting in T cell secretion of IL-21, which, in turn induced B cell differentiation through the IL-21R/STAT3/Blimp-1 pathway.ConclusionsCRA regulated T cell activity resulting in B cell activation and triggering of anti-tumor antibodies to impede CRC progression.

Membrane fusion-mediated delivery of small-molecule HER2 tyrosine kinase inhibitor for effective tumor chemosensitization

Although nanocarriers have been widely applied in the delivery of anticancer drugs, many commercialized anticancer nanodrug systems still suffer from the problem of being easily trapped by lysosomes, which severely limits the drug delivery efficiency of a nanodrug system. Meanwhile, in drug-resistant tumors, the efflux of anticancer therapeutic drugs via the drug efflux transporters on the plasma membrane of cancer cells can significantly decrease the intracellular drug concentration and lead to the failure of the drug treatment. Here, we developed a small-molecule tyrosine kinase inhibitor (TKI)- and doxorubicin (Dox, a common anticancer drug)-loaded membrane fusion liposome (MFL) (termed Dox@Lapa-MFL) to achieve tumor cell membrane fusion-mediated drug delivery and enhanced chemotherapy of drug-resistant tumor. MFL could deliver drugs in a membrane fusion manner, circumventing the capture by lysosomes. Lapatinib, as the TKI doped in the MFL, could inhibit the efflux of Dox by ATP-binding cassette transporters (ABC transporters), further promoting the intracellular Dox accumulation. As a result, Dox achieved effective killing of drug-resistant tumors under the dual effect of MFL and lapatinib. To the best of our knowledge, it is the first example that employs membrane fusion-mediated TKI delivery for achieving tumor chemosensitization with good biosafety. This work presents an efficient and easily achievable strategy for treating drug-resistant tumors, which may hold promise for clinical applications.

Microtubule-associated protein MAP1LC3C regulates lysosomal exocytosis and induces zinc reprogramming in renal cancer cells

Microtubule-associated protein 1 light chain 3 gamma (MAP1LC3C or LC3C) is a member of the microtubule-associated family of proteins that are essential in the formation of autophagosomes and lysosomal degradation of cargo. LC3C has tumor-suppressing activity, and its expression is dependent on kidney cancer tumor suppressors, such as von Hippel-Lindau protein and folliculin. Recently, we demonstrated that LC3C autophagy is regulated by noncanonical upstream regulatory complexes and targets for degradation postdivision midbody rings associated with cancer cell stemness. Here, we show that loss of LC3C leads to peripheral positioning of the lysosomes and lysosomal exocytosis (LE). This process is independent of the autophagic activity of LC3C. Analysis of isogenic cells with low and high LE shows substantial transcriptomic reprogramming with altered expression of zinc (Zn)-related genes and activity of polycomb repressor complex 2, accompanied by a robust decrease in intracellular Zn. In addition, metabolomic analysis revealed alterations in amino acid steady-state levels. Cells with augmented LE show increased tumor initiation properties and form aggressive tumors in xenograft models. Immunocytochemistry identified high levels of lysosomal-associated membrane protein 1 on the plasma membrane of cancer cells in human clear cell renal cell carcinoma and reduced levels of Zn, suggesting that LE occurs in clear cell renal cell carcinoma, potentially contributing to the loss of Zn. These data indicate that the reprogramming of lysosomal localization and Zn metabolism with implication for epigenetic remodeling in a subpopulation of tumor-propagating cancer cells is an important aspect of tumor-suppressing activity of LC3C.

What is thyroid function in your just-diagnosed cancer patient?

The principal hormonal product of the thyroid gland, L-thyroxine (T4), is a prohormone for 3,3',5-triiodo-L-thyronine, T3, the major ligand of nuclear thyroid hormone receptors (TRs). At a cell surface thyroid hormone analogue receptor on cancer cell and endothelial cell plasma membrane integrin αvβ3, however, T4 at physiological concentrations is biologically active and is the major ligand. At this site in solid tumor cells, T4 nongenomically initiates cell proliferation, is anti-apoptotic by multiple mechanisms, supports radioresistance and enhances cancer-related angiogenesis. In contrast, hypothyroidism has been reported clinically to slow tumor growth. At physiological levels, T3 is not biologically active at the integrin and maintenance of euthyroidism with T3 in cancer patients may be associated with slowed tumor proliferation. Against this background, we raise the possibility that host serum T4 levels that are spontaneously in the upper tertile or quartile of the normal range in cancer patients may be a factor that contributes to aggressive tumor behavior. Recent observations on tumor metastasis and tumor-associated propensity for thrombosis due to T4 also justify clinical statistical analysis for a relationship to upper tertile hormone levels. That reverse T3 (rT3) may stimulate tumor growth has recently been reported and thus the utility of adding this measurement to thyroid function testing in cancer patients requires assessment. In summary, T4 at physiological concentrations promotes tumor cell division and aggressiveness and euthyroid hypothyroxinemia arrests clinically advanced solid tumors. These findings support the clinical possibility that T4 levels in the upper tertile of the normal range require examination as a tumor supporting factor.

PD-L1 translocation to the plasma membrane enables tumor immune evasion through MIB2 ubiquitination.

Programmed death-ligand 1 (PD-L1), a critical immune checkpoint ligand, is a transmembrane protein synthesized in the endoplasmic reticulum of tumor cells and transported to the plasma membrane to interact with programmed death 1 (PD-1) expressed on T cell surface. This interaction delivers coinhibitory signals to T cells, thereby suppressing their function and allowing evasion of antitumor immunity. Most companion or complementary diagnostic devices for assessing PD-L1 expression levels in tumor cells used in the clinic or in clinical trials require membranous staining. However, the mechanism driving PD-L1 translocation to the plasma membrane after de novo synthesis is poorly understood. Herein, we showed that mind bomb homolog 2 (MIB2) is required for PD-L1 transportation from the trans-Golgi network (TGN) to the plasma membrane of cancer cells. MIB2 deficiency led to fewer PD-L1 proteins on the tumor cell surface and promoted antitumor immunity in mice. Mechanistically, MIB2 catalyzed nonproteolytic K63-linked ubiquitination of PD-L1, facilitating PD-L1 trafficking through Ras-associated binding 8-mediated (RAB8-mediated) exocytosis from the TGN to the plasma membrane, where it bound PD-1 extrinsically to prevent tumor cell killing by T cells. Our findings demonstrate that nonproteolytic ubiquitination of PD-L1 by MIB2 is required for its transportation to the plasma membrane and tumor cell immune evasion.

Immunohistochemical Analysis of Common Cancer Antigens in Head and Neck Squamous Cell Carcinoma

The prognosis of recurring and metastatic head and neck squamous cell carcinoma (HNSCC) is poor. Although immune checkpoint inhibitors have expanded the treatment options for HNSCC, the response rates are low. Alternatively, cancer vaccines and T-cell therapies are being developed. Identification of useful common cancer antigens and confirmation of human leukocyte antigen (HLA) class I expression are required. Immunohistochemistry analyses were performed for 10 antigens (FOXM1, TGFBI, SPARC, HSP105α, WT1, AFP, GPC3, PP-RP, KIF20A, KM-HN-1) and HLA class I using specimens of 56 surgical cases. Staining intensity, percentage of stain-positive areas, and localization of staining in the tumor cells and normal tissue were evaluated. Staining of FOXM1, TGFBI, SPARC, and HSP105α was more predominant in tumor cells than that in normal cells. The expression rates of these antigens in tumor cells were 60.7%, 58.9%, 73.2%, and 50.0%, respectively. Regarding sites, the expression rates of these antigens in oral cancer were high at 57.1%, 71.4%, 81.0%, and 66.7%, respectively. Furthermore, the expression of HLA class I was 83.9% in all cases. Of these, 68.1% showed expression on the plasma membrane. FOXM1, TGFBI, SPARC, and HSP105α could be useful common cancer antigens, and HLA class I is expressed on the plasma membrane of cancer cells in many cases. The results suggest that cancer vaccines and T-cell therapy may be clinically viable options for HNSCC treatment.

Benzoate group attachment to TEMPO provides enhanced discrimination of liposomes fabricated using human lung normal and carcinoma cells

It is widely accepted that the lipid compositions of the plasma membranes of healthy and cancer cells significantly differ from each other. During the cancer progression, cancer cells change the lipid constituent of the membranes resulting in the loss of lipid asymmetry between the membrane leaflets. Consequently, physicochemical properties of the cell membranes are also changed in response to altered lipid organization. Partitioning of the spin probe 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) into the membranes of the cells has broadly been applied to characterize membrane properties of various cells in health and disease conditions. In this work, we used liposomes fabricated using lipids extracted from normal and carcinoma cells. This system permits the determination of the properties of the healthy and cancer cell membranes provided exclusively by its lipid components. Application of TEMPO-benzoate, in which the benzoate group is attached to the TEMPO, indicates significantly enhanced discrimination of liposomes between cancer and normal cells. Partitioning experiments with TEMPO-benzoate revealed relatively enhanced incorporation efficiency for liposomes of cancer cells. On the contrary, TEMPO incorporation efficiency in the same liposomes of cancer cells was not much different compared to healthy cells. Data indicate that TEMPO-benzoate as a probe is more suitable than TEMPO to discriminate cancer cells from healthy cells. Free energy gain observed for TEMPO-benzoate resulted mainly from the hydrophobic effect of the benzoate group.

Alteration of cholesterol distribution at the plasma membrane of cancer cells: From evidence to pathophysiological implication and promising therapy strategy.

Cholesterol-enriched domains are nowadays proposed to contribute to cancer cell proliferation, survival, death and invasion, with important implications in tumor progression. They could therefore represent promising targets for new anticancer treatment. However, although diverse strategies have been developed over the years from directly targeting cholesterol membrane content/distribution to adjusting sterol intake, all approaches present more or less substantial limitations. Those data emphasize the need to optimize current strategies, to develop new specific cholesterol-targeting anticancer drugs and/or to combine them with additional strategies targeting other lipids than cholesterol. Those objectives can only be achieved if we first decipher (i) the mechanisms that govern the formation and deformation of the different types of cholesterol-enriched domains and their interplay in healthy cells; (ii) the mechanisms behind domain deregulation in cancer; (iii) the potential generalization of observations in different types of cancer; and (iv) the specificity of some alterations in cancer vs. non-cancer cells as promising strategy for anticancer therapy. In this review, we will discuss the current knowledge on the homeostasis, roles and membrane distribution of cholesterol in non-tumorigenic cells. We will then integrate documented alterations of cholesterol distribution in domains at the surface of cancer cells and the mechanisms behind their contribution in cancer processes. We shall finally provide an overview on the potential strategies developed to target those cholesterol-enriched domains in cancer therapy.