The AKT-independent MET-V-ATPase-MTOR axis suppresses liver cancer vaccination

Extracellular Glutamine Promotes Intestinal Porcine Epithelial Cell Proliferation via Arf1-mTORC1 Pathway Independently of Rag GTPases

Glutamine (Gln) is the major energy source of intestinal porcine epithelial cells (IPEC-J2 cells) and plays a critical role in the nutritional physiological function of the intestine. However, the underlying mechanism requires further investigation. Here, the Gln-sensing pathway in IPEC-J2 cells was investigated. The results showed that Gln increased the cell proliferation. Subsequently, an analysis of the phosphorylated proteome revealed that Gln markedly upregulated ribosomal protein S6 (RPS6) phosphorylation at serine 235/236, suggesting that Gln activated the mTORC1 pathway. mTOR inhibition revealed that Gln promotes cell proliferation through the mTORC1 pathway. Similarly, blocking ADP-ribosylation factor 1 (Arf1) activity indicated that Gln-induced mTORC1 activation promoted cell proliferation in an Arf1-dependent manner. Additionally, the RagA/B pathway did not participate in Gln-induced mTORC1 activation. Collectively, these findings suggest that Gln-induced mTORC1 activation promotes IPEC-J2 cell proliferation via Arf1, not Rag GTPases. These results broaden our understanding of functional-cell-sensing amino acids, particularly Gln, that are regulated by mTORC1.

Vacuolar ATPase Is a Possible Therapeutic Target in Acute Myeloid Leukemia: Focus on Patient Heterogeneity and Treatment Toxicity

Vacuolar ATPase (V-ATPase) is regarded as a possible target in cancer treatment. It is expressed in primary acute myeloid leukemia cells (AML), but the expression varies between patients and is highest for patients with a favorable prognosis after intensive chemotherapy. We therefore investigated the functional effects of two V-ATPase inhibitors (bafilomycin A1, concanamycin A) for primary AML cells derived from 80 consecutive patients. The V-ATPase inhibitors showed dose-dependent antiproliferative and proapoptotic effects that varied considerably between patients. A proteomic comparison of primary AML cells showing weak versus strong antiproliferative effects of V-ATPase inhibition showed a differential expression of proteins involved in intracellular transport/cytoskeleton functions, and an equivalent phosphoproteomic comparison showed a differential expression of proteins that regulate RNA processing/function together with increased activity of casein kinase 2. Patients with secondary AML, i.e., a heterogeneous subset with generally adverse prognosis and previous cytotoxic therapy, myeloproliferative neoplasia or myelodysplastic syndrome, were characterized by a strong antiproliferative effect of V-ATPase inhibition and also by a specific mRNA expression profile of V-ATPase interactome proteins. Furthermore, the V-ATPase inhibition altered the constitutive extracellular release of several soluble mediators (e.g., chemokines, interleukins, proteases, protease inhibitors), and increased mediator levels in the presence of AML-supporting bone marrow mesenchymal stem cells was then observed, especially for patients with secondary AML. Finally, animal studies suggested that the V-ATPase inhibitor bafilomycin had limited toxicity, even when combined with cytarabine. To conclude, V-ATPase inhibition has antileukemic effects in AML, but this effect varies between patients.

Oncolytic peptide LTX-315 induces anti-pancreatic cancer immunity by targeting the ATP11B-PD-L1 axis

Background

LTX-315 is an oncolytic peptide deriving from bovine lactoferrin, with the ability to induce cancer immunogenic cell death. However, the mechanism used by LTX-315 to trigger the antitumor immune response is still poorly understood. The expression of programmed cell death ligand 1 (PD-L1) largely determines the efficacy and effectiveness of cancer immunotherapies targeting this specific immune checkpoint. This study aimed to demonstrate the potential effect and mechanism of LTX-315 in PD-L1 inhibition-induced anti-pancreatic cancer immunity.

Methods

Both immunodeficient and immunocompetent mouse models were used to evaluate the therapeutic efficacy of monotherapy and combination therapy. Flow cytometry and immunohistochemistry were used to assess the immune microenvironment. Multiomic analysis was used to identify the potential target and down-streaming signaling pathway. Both in-house tissue microarray and open accessed The Cancer Genome Atlas data sets were used to evaluate the clinical relevance in pancreatic cancer prognosis.

Results

LTX-315 treatment inhibited PD-L1 expression and enhanced lymphocyte infiltration in pancreatic tumors. ATP11B was identified as a potential target of LTX-315 and a critical regulator in maintaining PD-L1 expression in pancreatic cancer cells. As regards the mechanism, ATP11B interacted with PD-L1 in a CKLF-like MARVEL transmembrane domain containing 6 (CMTM6)-dependent manner. The depletion of ATP11B promoted CMTM6-mediated lysosomal degradation of PD-L1, thus reactivating the immune microenvironment and inducing an antitumor immune response. The significant correlation among ATP11B, CMTM6, and PD-L1 was confirmed in clinical samples of pancreatic cancer.

Conclusions

LTX-315 was first identified as a peptide drug inducing PD-L1 downregulation via ATP11B. Therefore, LTX-315, or the development of ATP11B-targeting drugs, might improve the efficacy of cancer immunotherapy.

Anti-Cancer Activity of Phytochemicals Targeting Hypoxia-Inducible Factor-1 Alpha

Hypoxia-inducible factor-1 alpha (HIF-1α) is overexpressed in cancer, leading to a poor prognosis in patients. Diverse cellular factors are able to regulate HIF-1α expression in hypoxia and even in non-hypoxic conditions, affecting its progression and malignant characteristics by regulating the expression of the HIF-1α target genes that are involved in cell survival, angiogenesis, metabolism, therapeutic resistance, et cetera. Numerous studies have exhibited the anti-cancer effect of HIF-1α inhibition itself and the augmentation of anti-cancer treatment efficacy by interfering with HIF-1α-mediated signaling. The anti-cancer effect of plant-derived phytochemicals has been evaluated, and they have been found to possess significant therapeutic potentials against numerous cancer types. A better understanding of phytochemicals is indispensable for establishing advanced strategies for cancer therapy. This article reviews the anti-cancer effect of phytochemicals in connection with HIF-1α regulation.

Combinational blockade of MET and PD-L1 improves pancreatic cancer immunotherapeutic efficacy

BACKGROUND

Dysregulated expression and activation of receptor tyrosine kinases (RTKs) are associated with a range of human cancers. However, current RTK-targeting strategies exert little effect on pancreatic cancer, a highly malignant tumor with complex immune microenvironment. Given that immunotherapy for pancreatic cancer still remains challenging, this study aimed to elucidate the prognostic role of RTKs in pancreatic tumors with different immunological backgrounds and investigate their targeting potential in pancreatic cancer immunotherapy.

METHODS

Kaplan-Meier plotter was used to analyze the prognostic significance of each of the all-known RTKs to date in immune "hot" and "cold" pancreatic cancers. Gene Expression Profiling Interactive Analysis-2 was applied to assess the differential expression of RTKs between pancreatic tumors and normal pancreatic tissues, as well as its correlation with immune checkpoints (ICPs). One hundred and fifty in-house clinical tissue specimens of pancreatic cancer were collected for expression and correlation validation via immunohistochemical analysis. Two pancreatic cancer cell lines were used to demonstrate the regulatory effects of RTKs on ICPs by biochemistry and flow cytometry. Two in vivo models bearing pancreatic tumors were jointly applied to investigate the combinational regimen of RTK inhibition and immune checkpoint blockade for pancreatic cancer immunotherapy.

RESULTS

MET was identified as a pancreatic cancer-specific RTK, which is significantly associated with prognosis in both immune "hot" and "cold" pancreatic cancers. MET was observed to be highly upregulated in pancreatic cancer tissues, and positively correlated with PD-L1 levels. Elevated MET and PD-L1 expressions were closely associated with lymph node metastasis, tumor TNM stage, and overall survival in pancreatic cancer. Mechanistically, MET could interact with PD-L1, and maintain its expression level in multiple ways. MET deficiency was found to facilitate lymphocyte infiltration into pancreatic tumors. Finally, significant benefits of combining MET inhibition with PD-1/PD-L1 blockage were verified in both orthotopic and subcutaneous mouse models of pancreatic cancer.

CONCLUSIONS

This study systematically investigated the potential effectiveness of a novel pancreatic cancer immunotherapy targeting RTKs, and revealed the function of MET in PD-L1 regulation as well as the combined therapeutic efficacy of MET and PD-L1 in pancreatic cancer.

Inhibiting ATP6V0D2 Aggravates Liver Ischemia-Reperfusion Injury by Promoting NLRP3 Activation via Impairing Autophagic Flux Independent of Notch1/Hes1

At present, liver ischemia-reperfusion (IR) injury is still a great challenge for clinical liver partial resection and liver transplantation. The innate immunity regulated by liver macrophages orchestrates the cascade of IR inflammation and acts as a bridge. As a specific macrophage subunit of vacuolar ATPase, ATP6V0D2 (V-ATPase D2 subunit) has been shown to promote the formation of autophagolysosome in vitro. Our research fills a gap which has existed in the study of inflammatory stress about the V-ATPase subunit ATP6V0D2 in liver macrophages. We first found that the expression of specific ATP6V0D2 in liver macrophages was upregulated with the induction of inflammatory cascade after liver IR surgery, and knockdown of ATP6V0D2 resulted in increased secretion of proinflammatory factors and chemokines, which enhanced activation of NLRP3 and aggravation of liver injury. Further studies found that the exacerbated activation of NLRP3 was related to the autophagic flux regulated by ATP6V0D2. Knocking down ATP6V0D2 impaired the formation of autophagolysosome and aggravated liver IR injury through nonspecific V-ATPase activation independent of V-ATPase-Notchl-Hesl signal axis. In general, we illustrated that the expression of ATP6V0D2 in liver macrophages was upregulated after liver IR, and by gradually promoting the formation of autophagolysosomes to increase autophagy flux to limit the activation of liver inflammation, this regulation is independent of the Notch1-Hes1 signal axis.

Combinational therapy targeting the MET-mTOR-ROS loop disrupts mitochondrial autoregulatory machinery of liver cancer

A wide variety of regulators have been identified in mechanistic target of rapamycin (mTOR) activation; however, the protective mechanisms of mTOR inactivation are still largely unknown, especially in tumor growth. Here, we have found the hepatocyte growth factor (HGF) receptor (MET) is required for mTOR activation-stimulated mitochondrial oxidative phosphorylation (OXPHOS) in a phosphorylation-dependent manner in liver cancer. Intriguingly, we observed mitochondrial quality dictates the regulatory effects of MET on mTOR and OXPHOS. Once overloaded, mitochondrial reactive oxygen species (ROS) inhibits mTOR activity and OXPHOS performance to prevent mitochondrial dysfunction-induced tumor cell death, by disrupting MET dimerization to block its autophosphorylation and interaction with vacuolar ATP synthase (V-ATPase). The MET-mTOR-ROS loop acts as a protective checkpoint in liver cancer, and thus this autoregulatory machinery is a promising combinational target for liver cancer therapy.

Genomic investigation of co-targeting tumor immune microenvironment and immune checkpoints in pan-cancer immunotherapy

Drugs that target immune checkpoints (ICPs) have become the most popular weapons in cancer immunotherapy; however, they are only beneficial for a small fraction of patients. Accumulating evidence suggests that the tumor immune microenvironment (TIME) plays a critical role in anti-cancer immunity. This study aimed to assess the potential merits and feasibility of combinational targeting ICPs and TIME in cancer immunotherapy. A total of 31 cancer type-specific datasets in TCGA were individually collected by the publicly available web servers for multiple bioinformatic analyses of ICPs and TIME factors. GEPIA was used to calculate the prognostic indexes, STRING was used to construct protein-protein interactions, cBioPortal was used for visualization and comparison of genetic alterations, and TISIDB was used to explore the correlation to tumor-infiltrating lymphocytes (TILs). Intriguingly, TIME factors were identified to have more global coverage and prognostic significance across multiple cancer types compared with ICPs, thus offering more general targetability in clinical therapy. Moreover, TIME factors showed interactive potential with ICPs, and genomic alteration of TIME factors coupled with that of ICPs, at least in pancreatic cancer. Furthermore, TIME factors were found to be significantly associated with TILs, including but not limited to pancreatic cancer. Finally, the clinical significance and translational potential of further combination therapies that incorporate both ICP inhibitors and TIME factor-targeted treatments were discussed. Together, TIME factors are promising immunotherapeutic targets, and a combination strategy of TIME factors-targeted therapies with ICP inhibitors may benefit more cancer patients in the future.

Reviving the role of MET in liver cancer therapy and vaccination: an autophagic perspective

Past failures in clinical trials have dampened the enthusiasm for studying the HGF receptor MET and postponed the development of MET-targeted drugs for cancer therapy. However, new evidence suggests that, at least in liver cancer, MET is still a promising therapeutic target, and may also be a potential target for cancer vaccines. This paper briefly highlights novel research advances in this rapidly-evolving field in the perspective of autophagy, and discusses future directions for further investigation of MET-based cancer therapy and vaccination.