Inhibit Tumor Cell Research Articles

Bacterial Flagellum-Drug Nanoconjugates for Carrier-Free Immunochemotherapy.

The combination of immunotherapy and chemotherapy to ablate tumors has attracted substantial attention due to the ability to simultaneously elicit antitumor immune responses and trigger direct tumor cell death. However, conventional combinational strategies mainly focus on the employment of drug carriers to deliver immunomodulators, chemotherapeutics, or their combinations, always suffering from complicated preparation and carrier-relevant side effects. Here, the fabrication of bacterial flagellum-drug nanoconjugates (FDNCs) for carrier-free immunochemotherapy is described. FDNCs are simply prepared by attaching chemotherapeutics to amine residues of flagellin through an acid-sensitive and traceless cis-aconityl linker. By virtue of native nanofibrous structure and immunogenicity, bacterial flagella not only show long-term tumor retention and highly efficient cell internalization, but also provoke robust systemic antitumor immune responses. Meanwhile, conjugated chemotherapeutics exhibit an acid-mediated release profile and durable intratumoral exposure, which can induce potent tumor cell inhibition via direct killing. More importantly, this combination is able to augment immunoactivation effects associated with chemotherapy-enabled immunogenic tumor cell death to further enhance antitumor efficacy. By leveraging the innate response of the immune system to pathogens, the conjugation of therapeutic agents with self-adjuvant bacterial flagella provides an alternative approach to develop carrier-free nanotherapeutics for tumor immunochemotherapy.

Retracted] miR‑206 inhibits cancer initiating cells by targeting EHF in gastric cancer.

Following the publication of this paper, it was drawn to the Editor's attention by a concerned reader that the colony formation assay data shown in Figs.2, 4 and 8 were strikingly similar to data that had already appeared in another article written by different authors at different research institutes [ChenW, Wang J, Liu S, Wang S, Cheng Y, Zhou W, DuanC and ZhangC: MicroRNA‑361‑3p suppresses tumor cell proliferation and metastasis by directly targeting SH2B1 in NSCLC. J Exp Clin Cancer Res35: 76, 732516, 2016]. Owing to the fact that the contentious data in the above article had already been published prior to its submission to Oncology Reports, the Editor has decided that this paper should be retracted from the Journal. The authors were asked for an explanation to account for these concerns, but the Editorial Office did not receive a reply. The Editor apologizes to the readership for any inconvenience caused. [Oncology Reports 38: 1688‑1694, 2017; DOI: 10.3892/or.2017.5794].

Hormetic and synergistic effects of cancer treatments revealed by modelling combinations of radio - or chemotherapy with immunotherapy

BackgroundRadio/chemotherapy and immune systems provide examples of hormesis, as tumours can be stimulated (or reduced) at low radio/chemical or antibody doses but inhibited (or stimulated) by high doses.MethodsInteractions between effector cells, tumour cells and cytokines with pulsed radio/chemo-immunotherapy were modelled using a pulse differential system.ResultsOur results show that radio/chemotherapy (dose) response curves (RCRC) and/or immune response curves (IRC) or a combination of both, undergo homeostatic changes or catastrophic shifts revealing hormesis in many parameter regions. Some mixed response curves had multiple humps, posing challenges for interpretation of clinical trials and experimental design, due to a fuzzy region between an hormetic zone and the toxic threshold. Mixed response curves from two parameter bifurcation analyses demonstrated that low-dose radio/chemotherapy and strong immunotherapy counteract side-effects of radio/chemotherapy on effector cells and cytokines and stimulate effects of immunotherapy on tumour growth. The implications for clinical applications were confirmed by good fits to our model of RCRC and IRC data.ConclusionsThe combination of low-dose radio/chemotherapy and high-dose immunotherapy is very effective for many solid tumours. The net benefit and synergistic effect of combined therapy is conducive to the treatment and inhibition of tumour cells.

Human diet-derived polyphenolic compounds and hepatic diseases: From therapeutic mechanisms to clinical utilization.

This review focuses on the potential ameliorative effects of polyphenolic compounds derived from human diet on hepatic diseases. It discusses the molecular mechanisms and recent advancements in clinical applications. Edible polyphenols have been found to play a therapeutic role, particularly in liver injury, liver fibrosis, NAFLD/NASH, and HCC. In the regulation of liver injury, polyphenols exhibit anti-inflammatory and antioxidant effects, primarily targeting the TGF-β, NF-κB/TLR4, PI3K/AKT, and Nrf2/HO-1 signaling pathways. In the regulation of liver fibrosis, polyphenolic compounds effectively reverse the fibrotic process by inhibiting the activation of hepatic stellate cells (HSC). Furthermore, polyphenolic compounds show efficacy against NAFLD/NASH by inhibiting lipid oxidation and accumulation, mediated through the AMPK, SIRT, and PPARγ pathways. Moreover, several polyphenolic compounds exhibit anti-HCC activity by suppressing tumor cell proliferation and metastasis. This inhibition primarily involves blocking Akt and Wnt signaling, as well as inhibiting the epithelial-mesenchymal transition (EMT). Additionally, clinical trials and nutritional evidence support the notion that certain polyphenols can improve liver disease and associated metabolic disorders. However, further fundamental research and clinical trials are warranted to validate the efficacy of dietary polyphenols.

A double-gain theranostic nanoplatform based on self-supplying H2O2 nanocomposites for synergistic chemodynamic/gas therapy

Chemodynamic therapy (CDT) based on hydroxyl radicals (•OH) to suppress tumor cells is a promising strategy due to its efficacy and safety. Nevertheless, in tumor cells, CDT still faces challenges such as insufficient •OH and weak killing effect of tumor cells under physiological conditions due to inadequate amounts of endogenous hydrogen peroxide (H2O2) and heightened glutathione expression. These challenges limit the therapeutic potential of CDT. To improve the effects of CDT, combination treatment strategies have been developed. Here, we report a rationally designed nanocomposite (CaO2@Cu-LA) with self-supplying H2O2 ability from calcium peroxide, and nitric oxide (NO) generation ability from l-arginine. NO molecules not only exhibit a strong killing effect, but also have the potential to transfer into the more cytotoxic substance peroxynitrite anion by reacting with reactive oxygen species. The results showed that CaO2@Cu-LA could significantly suppress tumor growth by increasing •OH radicals and NO molecules. Taken together, the strategy developed here provides a good application foreground to yield a remarkable synergistic antitumor effect of CDT and NO gas therapy.

TIM-3 blockade in diffuse intrinsic pontine glioma models promotes tumor regression and antitumor immune memory

Diffuse intrinsic pontine glioma (DIPG) is an aggressive brain stem tumor and the leading cause of pediatric cancer-related death. To date, these tumors remain incurable, underscoring the need for efficacious therapies. In this study, we demonstrate that the immune checkpoint TIM-3 (HAVCR2) is highly expressed in both tumor cells and microenvironmental cells, mainly microglia and macrophages, in DIPG. We show that inhibition of TIM-3 in syngeneic models of DIPG prolongs survival and produces long-term survivors free of disease that harbor immune memory. This antitumor effect is driven by the direct effect of TIM-3 inhibition in tumor cells, the coordinated action of several immune cell populations, and the secretion of chemokines/cytokines that create a proinflammatory tumor microenvironment favoring a potent antitumor immune response. This work uncovers TIM-3 as a bona fide target in DIPG and supports its clinical translation.

Growth inhibition of RAS-mutated hematopoietic tumor cells using glucose-attached reversibly ionic oligonucleotide-based nanoparticles caging chemically modified microRNA143-3p

Growth inhibition of RAS-mutated hematopoietic tumor cells using glucose-attached reversibly ionic oligonucleotide-based nanoparticles caging chemically modified microRNA143-3p

Direct regulation of FNIP1 and FNIP2 by MEF2 sustains MTORC1 activation and tumor progression in pancreatic cancer

ABSTRACT MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) orchestrates diverse environmental signals to facilitate cell growth and is frequently activated in cancer. Translocation of MTORC1 from the cytosol to the lysosomal surface by the RRAG GTPases is the key step in MTORC1 activation. Here, we demonstrated that transcription factors MEF2A and MEF2D synergistically regulated MTORC1 activation via modulating its cyto-lysosome shutting. Mechanically, MEF2A and MEF2D controlled the transcription of FNIP1 and FNIP2, the components of the FLCN-FNIP1 or FNIP2 complex that acts as a RRAGC-RRAGD GTPase-activating element to promote the recruitment of MTORC1 to lysosome and its activation. Furthermore, we determined that the pro-oncogenic protein kinase SRC/c-Src directly phosphorylated MEF2D at three conserved tyrosine residues. The tyrosine phosphorylation enhanced MEF2D transcriptional activity and was indispensable for MTORC1 activation. Finally, both the protein and tyrosine phosphorylation levels of MEF2D are elevated in human pancreatic cancers, positively correlating with MTORC1 activity. Depletion of both MEF2A and MEF2D or expressing the unphosphorylatable MEF2D mutant suppressed tumor cell growth. Thus, our study revealed a transcriptional regulatory mechanism of MTORC1 that promoted cell anabolism and proliferation and uncovered its critical role in pancreatic cancer progression. Abbreviation: ACTB: actin beta; ChIP: chromatin immunoprecipitation; EGF: epidermal growth factor; EIF4EBP1: eukaryotic translation initiation factor 4E binding protein 1; FLCN: folliculin; FNIP1: folliculin interacting protein 1; FNIP2: folliculin interacting protein 2; GAP: GTPase activator protein; GEF: guanine nucleotide exchange factors; GTPase: guanosine triphosphatase; LAMP2: lysosomal associated membrane protein 2; MAP1LC3B/LC3B: microtubule associated protein 1 light chain 3 beta; MEF2: myocyte enhancer factor 2; MEF2A: myocyte enhancer factor 2A; MEF2D: myocyte enhancer factor 2D; MEF2D-3YF: Y131F, Y333F, Y337F mutant; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; NR4A1: nuclear receptor subfamily 4 group A member 1; RPTOR: regulatory associated protein of MTOR complex 1; RHEB: Ras homolog, mTORC1 binding; RPS6KB1: ribosomal protein S6 kinase B1; RRAG: Ras related GTP binding; RT-qPCR: real time-quantitative PCR; SRC: SRC proto-oncogene, non-receptor tyrosine kinase; TMEM192: transmembrane protein 192; WT: wild-type.

Tumor-selective Blockade of CD47 Signaling with CD47 Antibody for Enhanced Anti-tumor Activity in Malignant Meningioma.

Patients with WHO grade III meningioma have a poor prognosis with a median survival of less than two years and a high risk of recurrence. However, traditional treatment options have failed to improve prognosis. Therefore, development of novel immunotherapy targets is urgently needed. CD47 acting as a "don't eat me" signal to macrophages can trigger tumor immune escape. However, the role of CD47 in malignant meningioma is not well understood. We collected 190 clinical meningioma samples and detected the expression of CD47 and immune infiltration in WHO grade I-III by immunohistochemistry, western blot, qPCR. We also examined the functional effects of anti-CD47 on cell proliferation, migration and invasion, macrophagemediated phagocytosis and tumorigenicity both in vitro and in vivo. We found that the expression of CD47 was increased in malignant meningioma along with a decreased number of T cells and an increase in CD68+ macrophages. Blocking CD47 with anti-CD47 antibody (B6H12) suppressed tumor cell growth, motility and promoted macrophage-mediated phagocytosis in IOMM-Lee cells in vitro. In vivo experiments showed that anti-CD47 antibody (B6H12 or MIAP301) significantly inhibited the tumor growth and this effect was partly blocked by the depletion of macrophages. Finally, p-ERK and EGFR showed higher expression in malignant meningioma with high expression of CD47, which was verified by western blot. Our results demonstrated that CD47 maybe involved in the meningioma progression and prognosis and offered a novel therapeutic option by targeting CD47 in malignant meningioma.

Anticancer Analysis of CD44 Targeted Cyclosporine Loaded Thiolated Chitosan Nanoformulations for Sustained Release in Triple-Negative Breast Cancer.

Cyclosporine (CsA), a potent immunosuppressive chemotherapeutic medication, treats numerous cancers, particularly malignant carcinoma, acute leukemia, and triple-negative breast cancer (TNBC). A specified polymeric nanoformulation (NF) based drug delivery technique with ligand functionalization at the surface was developed to improve its delivery at the intended area and boost the efficacy for prolonged time. The in silico verified the HA binding to the CD44 receptor at binding sites A and B in triple-negative breast cancer cells. The NF of encapsulated Cyclosporine in thiolated chitosan (TC) with the outermost coating of hyaluronic acid (HA) was formulated and characterized. So, the zeta analysis revealed a particle size of 192 nm and PDI of 0.433, zeta potential of 38.9mV. FTIR and Raman investigations also support the existence of hydrophobic groups, porous surfaces, and non-clumping characteristics. While XRD verified its crystallographic nature while SEM and TEM analysis revealed the spherical nanoparticles with sleek exteriors. DSC demonstrated the stability of NF at high temperatures. The NF showed 85% drug encapsulation followed Higuchi release model for therapeutic moiety at acidic pH for a maximum of 72 hours. When compared to raw Cyclosporine, the in vitro tumor cell inhibition of ThC-HA encapsulated with Cyclosporine was tested using an MTT dye on normal breast epithelial cells compared to triple-negative breast cancer cells. This novel formulation improved the long-term viability, effectiveness, and active targeting as an effective and potent therapeutic moiety against cancer.

Selective adhesion inhibition and hyaluronan envelope reduction of dermal tumor cells by cold plasma-activated medium

ABSTRACT The sensitivity to cold plasma is specific to tumor cells while leaving normal tissue cells unaffected. This is the desired challenge in cancer therapy. Therefore, the focus of this work was a comparative study concerning the plasma sensitivity of dermal tumor cells (A-431) versus non-tumorigenic dermal cells (HaCaT) regarding their adhesion capacity. We found a selective inhibiting effect of plasma-activated medium on the adhesion of tumor cells while hardly affecting normal cells. We attributed this to a lower basal gene expression for the adhesion-relevant components CD44, hyaluronan synthase 2 (HAS2), HAS3, and the hyaluronidases in A431. Noteworthy, after plasma exposure, we revealed a significantly higher expression and synthesis of the hyaluronan envelope, the HAS3 gene, and the transmembrane adhesion receptors in non-tumorigenic HaCaTs.

Long-read sequencing reveals the landscape of aberrant alternative splicing and novel therapeutic target in colorectal cancer

BackgroundAlternative splicing complexity plays a vital role in carcinogenesis and cancer progression. Improved understanding of novel splicing events and the underlying regulatory mechanisms may contribute new insights into developing new therapeutic strategies for colorectal cancer (CRC).MethodsHere, we combined long-read sequencing technology with short-read RNA-seq methods to investigate the transcriptome complexity in CRC. By using experiment assays, we explored the function of newly identified splicing isoform TIMP1 Δ4-5. Moreover, a CRISPR/dCasRx-based strategy to induce the TIMP1 exon 4–5 exclusion was introduced to inhibit neoplasm growth.ResultsA total of 90,703 transcripts were identified, of which > 62% were novel compared with current transcriptome annotations. These novel transcripts were more likely to be sample specific, expressed at relatively lower levels with more exons, and oncogenes displayed a characteristic to generate more transcripts in CRC. Clinical outcome data analysis showed that 1472 differentially expressed alternative splicing events (DEAS) were tightly associated with CRC patients’ prognosis, and many novel isoforms were likely to be important determinants for patient survival. Among these, newly identified splicing isoform TIMP1 Δ4-5 was significantly downregulated in CRC. Further in vitro and in vivo assays demonstrated that ectopic expression of TIMP1 Δ4-5 significantly suppresses tumor cell growth and metastasis. Serine/arginine-rich splicing factor 1 (SRSF1) acts as a onco-splicing regulator through sustaining the inclusion of TIMP1 exon 4–5. Furthermore, CRISPR/dCasRx-based strategies designed to induce TIMP1 exon 4–5 exclusion have the potential to restrain the CRC growth.ConclusionsThis data provides a rich resource for deeper studies of gastrointestinal malignancies. Newly identified splicing isoform TIMP1 Δ4-5 plays an important role in mediating CRC progression and may be a potential therapy target in CRC.

Reciprocal negative feedback regulation of ATF6α and PTEN promotes prostate cancer progression.

Phosphatase and tensin homolog (PTEN) loss tightly correlates with prostate cancer (PCa) progression and metastasis. Inactivation of PTEN leads to abnormal activation of PI3K/AKT pathway. However, results from clinical trials with AKT inhibitors in PCa have been largely disappointing. Identification of novel regulators of PTEN in PTEN-dysfunctional PCa is urgently needed. Here we demonstrated that the expression level of PTEN is inversely correlated with the signature score of unfolded protein response (UPR) in PCa. Importantly, PTEN suppresses the activity of ATF6α, via interacting to de-phosphorylate ATF6α and consequently inhibiting its nuclear translocation. Conversely, ATF6α promotes the ubiquitination and degradation of PTEN by inducing CHIP expression. Thus, ATF6α and PTEN forms a negative feedback loop during PCa progression. Combination of ATF6α inhibitor with AKT inhibitor suppresses tumor cell proliferation and xenograft growth. Importantly, this study highlighted ATF6α as a therapeutic vulnerability in PTEN dysfunctional PCa.

Machine learning developed a programmed cell death signature for predicting prognosis and immunotherapy benefits in lung adenocarcinoma

BackgroundLung cancer is the leading cause of cancer-related deaths worldwide with poor prognosis. Programmed cell death (PCD) plays a crucial function in tumor progression and immunotherapy response in lung adenocarcinoma (LUAD). MethodsIntegrative machine learning procedure including 10 methods was performed to develop a prognostic cell death signature (CDS) using TCGA, GSE30129, GSE31210, GSE37745, GSE42127, GSE50081, GSE68467, GSE68571, and GSE72094 dataset. The correlation between CDS and tumor immune microenvironment was evaluated using various methods and single cell analysis. qRT-PCR and CCK-8 assay were conducted to explore the biological functions of hub gene. ResultsThe prognostic CDS developed by Lasso + survivalSVM method was regarded as the optimal prognostic model. The CDS had a stable and powerful performance in predicting the clinical outcome of LUAD and served as an independent risk factor in TCGA and 8 GEO datasets. The C-index of CDS was higher than that of clinical stage and many developed signatures for LUAD. LUAD patients with low CDS score had a higher PD1&CTLA4 immunophenoscore, higher TMB score, lower TIDE score and lower tumor escape score, indicating a better immunotherapy benefit. Single cell analysis revealed a strong and frequent communication between epithelial cells and cancer-related fibroblasts by specific ligand-receptor pairs, including COL1A2-SDC4 and COL1A2-SDC1. Vitro experiment showed that SLC7A5 was upregulated in LUAD and knockdown of SLC7A5 obviously suppressed tumor cell proliferation. ConclusionOur study developed a novel CDS for LUAD. The CDS served as an indicator for predicting the prognosis and immunotherapy benefits of LAUD patients.

Abl kinases can function as suppressors of tumor progression and metastasis.

Abl family kinases function as proto-oncogenes in various leukemias, and pro-tumor functions have been discovered for Abl kinases in many solid tumors as well. However, a growing body of evidence indicates that Abl kinases can function to suppress tumor cell proliferation and motility and tumor growth in vivo in some settings. To investigate the role of Abl kinases in tumor progression, we used RNAi to generate Abl-deficient cells in a model of androgen receptor-indifferent, metastatic prostate cancer. The effect of Abl kinase depletion on tumor progression and metastasis was studied in an in vivo orthotopic model, and tumor cell motility, 3D growth, and signaling was studied in vitro. Reduced Abl family kinase expression resulted in a highly aggressive, metastatic phenotype in vivo that was associated with AKT pathway activation, increased growth on 3D collagen matrix, and enhanced cell motility in vitro. Inhibiting AKT pathway signaling abolished the increased 3D growth of Abl-deficient cells, while treatment with the Abl kinase inhibitor, imatinib, promoted 3D growth of multiple additional tumor cell types. Moreover, Abl kinase inhibition also promoted soft-agar colony formation by pre-malignant fibroblasts. Collectively, our data reveal that Abl family kinases can function to suppress malignant cell phenotypes in vitro, and tumor progression and metastasis in vivo.

Oridonin Synergistically Enhances the Pro-Apoptotic Effect of Venetoclax on Acute Myeloid Leukemia Cells by Inhibiting AKT Signaling.

Acute myeloid leukemia (AML) is a recurrence-prone hematologic malignancy. The advent of molecularly targeted therapies provides new opportunities to enhance the effectiveness of AML treatments. Venetoclax, a selective inhibitor of the anti-apoptotic protein Bcl-2, has shown promising results; however, resistance often arises due to elevated expression of the Mcl-1 protein, among other factors. Overcoming this resistance to improve therapeutic outcomes is a pressing issue that requires further investigation. Studies have demonstrated that oridonin, by inhibiting AKT signaling that regulates Mcl-1 expression, can effectively suppress tumor cell growth. This study aims to investigate whether oridonin can synergistically enhance the anti-leukemic effects of venetoclax and explore the underlying mechanisms behind this effect. In vitro experiments were performed to evaluate the effects of the combination of oridonin and venetoclax on AML cell proliferation, apoptosis, cell cycle distribution, and mitochondrial membrane potential. Transcriptome sequencing was used to elucidate the molecular mechanisms underlying the synergistic induction of AML cell apoptosis by the combination therapy. Western blotting and reverse transcription quantitative polymerase chain reaction (RT-qPCR) techniques were used to validate the findings. Additionally, an AML mouse model was established to observe the synergistic anti-AML effects of venetoclax combined with oridonin in vivo. Both venetoclax and oridonin individually exhibited inhibitory effects on AML cell proliferation, resulted in cell cycle arrest, and induced cell apoptosis. Moreover, combination of the two drugs resulted in a synergistic effect. We also observed that oridonin inhibited AKT phosphorylation, upregulated the expression of Bim and Bax proteins, facilitated Mcl-1 degradation, and enhanced the apoptotic effects of venetoclax in AML cells. Finally, in vivo experiments demonstrated that the combination of oridonin and venetoclax effectively inhibited the growth of AML xenograft tumors in mice and prolonged the survival time of tumor-bearing mice. Oridonin and venetoclax synergistically promote AML cell apoptosis by inhibiting AKT signaling.

Intelligent Responsive Nanoparticles with Multilevel Triggered Drug Penetration for Tumor Photochemotherapy.

Nanomedicines have contradictory size requirements to overcome systemic barriers and penetrate the tumor extracellular matrix (ECM). Larger-sized nanoparticles (50-200 nm) exhibit prolonged blood circulation half-life and improved tumor enrichment, while small-sized nanoparticles (4-20 nm) easily penetrate deep tumor tissues. Therefore, the development of intelligent responsive nanomedicine systems can not only increase nanodrug tumor accumulation but also improve their penetration into the ECM. Herein, we propose an intelligent responsive nanoparticle triggered by near-infrared light (NIR). The nanoparticle was constructed by a temperature-sensitive liposome (TSL) encapsulating ultrasmall melanin nanoparticles (MNPs) loaded with doxorubicin (MNP/doxorubicin (DOX)@TSL). When exposed to NIR irradiation, the tailor-made nanoparticles not only effectively ablated the tumor cells around blood vessels but also destroyed the structural integrity and released loaded ultrasmall MNP/DOX (<10 nm) to promote deep tumor penetration and enhance interior tumor cell killing. This NIR-triggered intelligent nanoparticle successfully integrated photothermal therapy (PTT) for perivascular tumor cells and chemotherapy for deep tumor cell inhibition. The in vivo results showed remarkable tumor regression in 4T1 breast tumor-bearing mice by 74.2%. This controllable size switchable nanosystem with efficient tumor accumulation and penetration has shown great potential in improving synergistic antitumor effects of photochemotherapy.

ATM inhibition augments type I interferon response and antitumor T-cell immunity when combined with radiation therapy in murine tumor models

BackgroundRadiation therapy (RT) elicits DNA double-strand breaks, resulting in tumor cytotoxicity and a type I interferon (IFN) response via stimulator of interferon genes (STING) activation. We investigated whether combining RT...

Attenuated Salmonella carrying siRNA-PD-L1 and radiation combinatorial therapy induces tumor regression on HCC through T cell-mediated immuno-enhancement

Hepatocellular carcinoma (HCC), the most prevalent type of aggressive liver cancer, accounts for the majority of liver cancer diagnoses and fatalities. Despite recent advancements in HCC treatment, it remains one of the deadliest cancers. Radiation therapy (RT) is among the locoregional therapy modalities employed to treat unresectable or medically inoperable HCC. However, radioresistance poses a significant challenge. It has been demonstrated that RT induced the upregulation of programmed death ligand 1 (PD-L1) on tumor cells, which may affect response to PD-1-based immunotherapy, providing a rationale for combining PD-1/PD-L1 inhibitors with radiation. Here, we utilized attenuated Salmonella as a carrier to explore whether attenuated Salmonella carrying siRNA-PD-L1 could effectively enhance the antitumor effect of radiotherapy on HCC-bearing mice. Our results showed that a combination of siRNA-PD-L1 and radiotherapy had a synergistic antitumor effect by inhibiting the expression of PD-L1 induced by radiation therapy. Mechanistic insights indicated that the combination treatment significantly suppressed tumor cell proliferation, promoted cell apoptosis, and stimulated immune cell infiltration and activation in tumor tissues. Additionally, the combination treatment increased the ratios of CD4+ T, CD8+ T, and NK cells from the spleen in tumor-bearing mice. This study presents a novel therapeutic strategy for HCC treatment, especially for patients with RT resistance.

Autocrine Factors Produced by Mesenchymal Stem Cells in Response to Cell-Cell Contact Inhibition Have Anti-Tumor Properties.

Recently, mesenchymal stem cell (MSC) therapies have been questioned as MSCs are capable of both promoting and inhibiting tumorigenesis. Both MSCs and tumor cells replicate to increase their population size; however, MSCs, but not tumor cells, stop dividing when they reach confluence due to cell-cell contact inhibition and then differentiate. We hypothesized that contact inhibition results in the production of effector molecules by confluent MSCs and these effectors are capable of suppressing tumor cell growth. To test this hypothesis, we co-cultured breast cancer cells (MDA-MB-231) with either confluent or sub-confluent bone-marrow-derived MSCs (BM-MSCs); in addition, we treated various tumor cells with conditioned media (CM) obtained from either confluent or sub-confluent BM-MSCs. The results showed that the growth of tumor cells co-cultured with confluent BM-MSCs or treated with CM obtained from confluent BM-MSCs was inhibited, and this effect was significantly stronger than that seen with tumor cells co-cultured with sub-confluent BM-MSCs or CM obtained from sub-confluent BM-MSCs. Subcutaneous tumor formation was completely prevented by the inoculation of tumor cells mixed with CM. In the future, soluble anti-tumor effectors, produced by confluent MSCs, may be used as cell-free therapeutics; this approach provides a solution to current concerns associated with cell-based therapies.