Molecular phenotypic linkage between N6-methyladenosine methylation and tumor immune microenvironment in hepatocellular carcinoma

PURPOSE

The crucial role of N6-methyladenosine (m6A) methylation in anti-tumor immunity and immunotherapy has been broadly depicted. However, the molecular phenotypic linkages between m6A modification pattern and immunological ecosystem are expected to be disentangled in hepatocellular carcinoma (HCC), for immunotherapeutic unresponsiveness circumvention and combination with promising drug agents.

METHODS

Modification patterns of m6A methylation were qualitatively dissected according to the large-scale HCC samples profiling. We then determined the immune phenotypic linkages by systematically evaluating their tumor microenvironment composition, immune/stromal-relevant signature, immune checkpoints correlation, and prognostic value. Individual quantification of m6A methylation pattern was achieved by m6Ascore construction, intensified by longitudinal single-cell analysis of immunotherapy cohort and validated by the transcriptomic profiles of our in-hospital GDPH-HCC cohort. Candidate therapeutic agents were also screened out.

RESULTS

Three distinct m6A methylation patterns were determined in high accordance with inflamed-, excluded-, and desert-immunophenotype. To be precise, Immune-inflamed high-m6Ascore group was characterized by activated immunity with favorable prognosis. Stromal activation and absence of immune cell infiltration were observed in low-m6Ascore phenotype, linked to impaired outcome. Patients with low-m6Ascore demonstrated diminished responses and clinical benefits for cohorts receiving immunotherapy. The above credible linkage between m6A methylation pattern and tumor immune microenvironment was robustly validated in our GDPH-HCC cohort. Single-cell dynamic change of m6A methylation level in exhausted CD8 T cell and fibroblast was depicted in immunotherapy cohort fore and art. Derived from m6A methylation pattern, seven potential frontline drug agents were recognized as promising choice for high-m6Ascore patients.

CONCLUSION

Our work bridged the credible linkage between epigenetics and anti-tumor immunity in HCC, unraveling m6A modification pattern as immunological indicator and predictor for immunotherapy. Individualized m6Ascore facilitated strategic choices to maximize therapy-responsive possibility.

Chloroquine regulates the proliferation and apoptosis of palate development on mice embryo by activating P53 through blocking autophagy in vitro

Cleft lip and palate is one of the most frequent congenital developmental defects. Autophagy is a highly conserved process of cell self-degradation in eukaryotes, involving multiple biological processes in which chloroquine (CQ) is the most common inhibitor. However, whether CQ affects and how it affects palate development is unknown. Mouse embryonic palatal cells (MEPCs) were treated with CQ to observe cell viability, apoptosis, migration, osteogenic differentiation by cell proliferation assay, flow cytometric analysis, scratch assay, and alizarin red staining. PI staining was used to measure cell cycle distribution. Immunofluorescence (IF) assay and transmission electron microscopy were used to detect autophagosomes. The autophagy-related factors (LC3 and P62), apoptosis-related markers (P53, caspase-3 cleaved caspase-3, BAX, and BCL-2), and cell cycle-related proteins (P21, CDK2, CDK4, cyclin D1, and cyclin E) were all measured by western blot. CQ inhibited the proliferation of MEPCs by arresting the G0/G1 phase of the cell cycle in a concentration- and time-dependent manner with cell cycle-related proteins P21 upregulated and CDK2, CDK4, cyclin D1, and cyclin E downregulated. Then we detected CQ also induced cell apoptosis in a dose-dependent manner by decreasing the BCL-2/BAX ratio and increasing cleaved caspase-3. Next, it was investigated that migration and osteogenesis of MEPCs decreased with CQ treatment in a dose-dependent manner. Meanwhile, CQ blocked the autophagy pathway by upregulating LC3II and P62 expressions which activated the P53 pathway. CQ activates P53 which affects MEPC biological characteristics by changing the proliferation and apoptosis of MEPCs through inhibiting autophagy.

Targeting breast cancer metabolism with a novel inhibitor of mitochondrial ATP synthesis

Inhibitors of mitochondrial respiration and ATP synthesis may promote the selective killing of respiration-competent cancer cells that are critical for tumor progression. We previously reported that CADD522, a small molecule inhibitor of the RUNX2 transcription factor, has potential for breast cancer treatment. In the current study, we show that CADD522 inhibits mitochondrial oxidative phosphorylation by decreasing the mitochondrial oxygen consumption rate (OCR) and ATP production in human breast cancer cells in a RUNX2-independent manner. The enzyme activity of mitochondrial ATP synthase was inhibited by CADD522 treatment. Importantly, results from cellular thermal shift assays that detect drug-induced protein stabilization revealed that CADD522 interacts with both α and β subunits of the F1-ATP synthase complex. Differential scanning fluorimetry also demonstrated interaction of α subunits of the F1-ATP synthase to CADD522. These results suggest that CADD522 might target the enzymatic F1 subunits in the ATP synthase complex. CADD522 increased the levels of intracellular reactive oxygen species (ROS), which was prevented by MitoQ, a mitochondria-targeted antioxidant, suggesting that cancer cells exposed to CADD522 may elevate ROS from mitochondria. CADD522-increased mitochondrial ROS levels were enhanced by exogenously added pro-oxidants such as hydrogen peroxide or tert-butyl hydroperoxide. Conversely, CADD522-mediated cell growth inhibition was blocked by N-acetyl-l-cysteine, a general ROS scavenger. Therefore, CADD522 may exert its antitumor activity by increasing mitochondrial driven cellular ROS levels. Collectively, our data suggest in vitro proof-of-concept that supports inhibition of mitochondrial ATP synthase and ROS generation as contributors to the effectiveness of CADD522 in suppression of tumor growth.

Developing TRAIL/TRAIL death receptor-based cancer therapies

Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) is a member of the TNF superfamily that can initiate the apoptosis pathway by binding to its associated death receptors DR4 and DR5. The activation of the TRAIL pathway in inducing tumor-selective apoptosis leads to the development of TRAIL-based cancer therapies, which include recombinant forms of TRAIL, TRAIL receptor agonists, and other therapeutic agents. Importantly, TRAIL, DR4, and DR5 can all be induced by synthetic and natural agents that activate the TRAIL apoptosis pathway in cancer cells. Thus, understanding the regulation of the TRAIL apoptosis pathway can aid in the development of TRAIL-based therapies for the treatment of human cancer.

RUNX3 enhances TRAIL-induced apoptosis by upregulating DR5 in colorectal cancer

RUNX3 is frequently inactivated by DNA hypermethylation in numerous cancers. Here, we show that RUNX3 has an important role in modulating apoptosis in immediate response to tumor necrosis factor-related apoptosis-including ligand (TRAIL). Importantly, no combined effect of TRAIL and RUNX3 was observed in non-cancerous cells. We investigated the expression of the death receptors (DRs) DR4 and DR5, which are related to TRAIL resistance. Overexpression of RUNX3 increased DR5 expression via induction of the reactive oxygen species (ROS)-endoplasmic reticulum (ER) stress-effector CHOP. Reduction of DR5 markedly decreased apoptosis enhanced by the combined therapy of TRAIL and RUNX3. Interestingly, RUNX3 induced reactive oxygen species production by inhibiting SOD3 transcription via binding to the Superoxide dismutase 3 (SOD3) promoter. Additionally, the combined effect of TRAIL and RUNX3 decreased tumor growth in xenograft models. Our results demonstrate a direct role for RUNX3 in TRAIL-induced apoptosis via activation of DR5 and provide further support for RUNX3 as an anti-tumor.

Enhancing tetrandrine cytotoxicity in human lung carcinoma A549 cells by suppressing mitochondrial ATP production

ATP depletion induced by inhibiting glycolysis or mitochondrial ATP production has been demonstrated to cause cancer cell death. Whether ATP depletion can enhance the efficacy and potency of anti-cancer effects of herbal compounds is so far unknown. We examined the enhancing effect of ATP depletion on anti-cancer actions of tetrandrine (TET) in human lung carcinoma A549 cells. A 24-h incubation of A549 cells with tetrandrine caused a concentration-dependent cytotoxic effect (LC₅₀ = 66.1 μM). Co-incubation with 20 mM 2-deoxyglucose (2-DG, glycolysis inhibitor) caused only a very slight enhancement of tetrandrine cytotoxicity. By contrast, inhibiting mitochondrial ATP production with oligomycin (10 μM, ATP synthase inhibitor) and FCCP (30 μM, uncoupling agent) (thus, oligo-FCCP) on its own caused only slight cell cytotoxicity but strongly potentiated tetrandrine cytotoxicity (tetrandrine LC₅₀ = 15.6 μM). The stronger enhancing effect of oligo-FCCP than 2-DG on TET toxicity did not result from more severe overall ATP depletion, since both treatments caused a similar ATP level suppression. Neither oligo-FCCP nor 2-DG synergized with tetrandrine in decreasing mitochondrial membrane potential. TET on its own triggered reactive oxygen species (ROS) production, and oligo-FCCP, but not 2-DG, potentiated TET in causing ROS production. Taken together, our results suggest that inhibiting ATP production from mitochondria, but not from glycolysis, appears to be a very effective means in augmenting TET-triggered ROS production and hence toxicity in A549 cells.

Autophagy inhibitor chloroquine induces apoptosis of cholangiocarcinoma cells via endoplasmic reticulum stress

Poor prognosis and chemotherapy tolerance are the main obstacles encountered in the treatment of cholangiocarcinoma. Chloroquine (CQ), an antimalarial agent, is able to induce sustained endoplasmic reticulum (ER) stress by functioning as an autophagy inhibitor. The present study indicated that CQ had the ability to induce apoptosis in QBC939 cholangiocarcinoma cells. Furthermore, using western blotting, Hoechst staining and flow cytometry, it was demonstrated that CQ induced the apoptosis of QBC939 cholangiocarcinoma cells. Analysis by a polymerase chain reaction (PCR) array and confirmation via quantitative PCR technology indicated that the expression levels of growth arrest and DNA damage 153 [C/EBP homologous protein (CHOP)], a key molecule involved in ER stress-induced apoptosis, and its downstream death receptors were increased following CQ stimulation. It was considered that the upregulation of CHOP may mediate CQ-induced extrinsic pathways and autophagy-dependent apoptosis; therefore, the role of autophagy in cholangiocarcinoma treatment was elucidated based on the data demonstrating that CQ regulates the ER-autophagy network in tumor cells. Furthermore, it was considered that CQ may become a novel and effective strategy for the treatment of cholangiocarcinoma.

Periostin has a protective role in melatonin‑induced cell apoptosis by inhibiting the eIF2α‑ATF4 pathway in human osteoblasts

The present study aimed to investigate the role of periostin (POSTN) and high melatonin concentrations in the apoptosis of hFOB 1.19 human normal fetal osteoblastic cells. hFOB 1.19 human osteoblastic cells were stably cultured and treated in different concentrations of melatonin for different durations of action. Apoptosis was assessed quantitatively using flow cytometric analysis. The results of western blot analysis demonstrated that the treatment of cells with different concentrations of melatonin for different durations of action revealed a positive association between melatonin and the expression levels of glucose‑regulated protein (GRP)78, GRP94, phosphorylated (p‑) eukaryotic initiation factor 2α (eIF2α), activating transcription factor (ATF)4, CCAAT/enhanced binding protein homologous protein (CHOP), cleaved caspase‑3, p‑c‑Jun N‑terminal kinase (JNK) and POSTN. When POSTN was inhibited, the levels of p‑JNK, CHOP, p‑eIF2α, ATF4 and cleaved caspase‑3 were significantly increased, whereas other proteins associated with the endoplasmic reticulum stress (ERS) pathways, including ATF6 and X‑box binding protein 1 (XBP1), were not significantly altered. Reverse transcription‑quantitative polymerase chain reaction analysis was also performed to assess the relative mRNA levels of ATF4, ATF6 and XBP1. The results of the present study are the first, to the best of our knowledge, to demonstrate that melatonin induced apoptosis in hFOB 1.19 human osteoblastic cells by activating the ERS‑associated eIF2α‑ATF4 pathway and subsequently triggered the cascade effects of CHOP, caspase‑3 and JNK. POSTN may function as a protective factor for osteoblasts during this process by inhibiting the eIF2α‑ATF4 pathway.

Glioma-derived cancer stem cells are hypersensitive to proteasomal inhibition

Although proteasome inhibitors (PIs) are used as anticancer drugs to treat various cancers, their relative therapeutic efficacy on stem cells vs. bulk cancers remains unknown. Here, we show that stem cells derived from gliomas, GSCs, are up to 1,000-fold more sensitive to PIs (IC₅₀, 27-70 nM) compared with their differentiated controls (IC₅₀, 47 to »100 μM). The stemness of GSCs correlates to increased ubiquitination, whose misregulation readily triggers apoptosis. PI-induced apoptosis of GSCs is independent of NF-κB but involves the phosphorylation of c-Jun N-terminal kinase as well as the transcriptional activation of endoplasmic reticulum (ER) stress-associated proapoptotic mediators. In contrast to the general notion that ER stress-associated apoptosis is signaled by prolonged unfolded protein response (UPR), GSC-selective apoptosis is instead counteracted by the UPR ATF3 is a key mediator in GSC-selective apoptosis. Pharmaceutical uncoupling of the UPR from its downstream apoptosis sensitizes GSCs to PIs in vitro and during tumorigenesis in mice. Thus, a combinational treatment of a PI with an inhibitor of UPR-coupled apoptosis may enhance targeting of stem cells in gliomas.

Valosin-containing Protein is a Target of 5'-l Fuligocandin B and Enhances TRAIL Resistance in Cancer Cells

Fuligocandin B (2) is a novel natural product that can overcome TRAIL resistance. We synthesized enatiomerically pure fuligocandin B (2) and its derivative 5′‐I fuligocandin B (4), and found that the latter had an improved biological activity against the human gastric cancer cell line, AGS. We attached a biotin linker and photoactivatable aryl diazirine group to 5′‐I fuligocandin B (4), and employed a pull‐down assay to identify valosin‐containing protein (VCP/p97), an AAA ATPase, as a 5′‐I fuligocandin B (4) target protein. Knock‐down of VCP by siRNA enhanced sensitivity to TRAIL in AGS cells. In addition, 4 enhanced CHOP and DR5 protein expression, and overall intracellular levels of ubiquitinated protein. These data suggest that endoplasmic reticulum stress caused through VCP inhibition by 4 increases CHOP‐mediated DR5 up‐regulation, which enhances TRAIL‐induced cell death in AGS cells. To the best of our knowledge, this is the first example to show a relationship between VCP and TRAIL‐resistance‐overcoming activity in cancer cells.

The acylphloroglucinols hyperforin and myrtucommulone A cause mitochondrial dysfunctions in leukemic cells by direct interference with mitochondria

The acylphloroglucinols hyperforin (Hypf) and myrtucommulone A (MC A) induce death of cancer cells by triggering the intrinsic/mitochondrial pathway of apoptosis, accompanied by a loss of the mitochondrial membrane potential and release of cytochrome c. However, the upstream targets and mechanisms leading to these mitochondrial events in cancer cells remain elusive. Here we show that Hypf and MC A directly act on mitochondria derived from human leukemic HL-60 cells and thus, disrupt mitochondrial functions. In isolated mitochondria, Hypf and MC A efficiently impaired mitochondrial viability (EC50 = 0.2 and 0.9 µM, respectively), caused loss of the mitochondrial membrane potential (at 0.03 and 0.1 µM, respectively), and suppressed mitochondrial ATP synthesis (IC50 = 0.2 and 0.5 µM, respectively). Consequently, the compounds activated the adenosine monophosphate-activated protein kinase (AMPK) in HL-60 cells, a cellular energy sensor involved in apoptosis of cancer cells. Side by side comparison with the protonophore CCCP and the ATP synthase inhibitor oligomycin suggest that Hypf and MC A act as protonophores that primarily dissipate the mitochondrial membrane potential by direct interaction with the mitochondrial membrane. Together, Hypf and MC A abolish the mitochondrial proton motive force that on one hand impairs mitochondrial viability and on the other cause activation of AMPK due to lowered ATP levels which may further facilitate the intrinsic mitochondrial pathway of apoptosis.

CCAAT-Enhancer-Binding Protein Homologous Protein Deficiency Attenuates Oxidative Stress and Renal Ischemia-Reperfusion Injury

AIMS

Renal ischemia-reperfusion (I/R) is a major cause of acute renal failure. The mechanisms of I/R injury include endoplasmic reticulum (ER) stress, inflammatory responses, hypoxia, and generation of reactive oxygen species (ROS). CCAAT/enhancer-binding protein (C/EBP) homologous protein (CHOP) is involved in the ER stress signaling pathways. CHOP is a transcription factor and a major mediator of ER stress-induced apoptosis. However, the role of CHOP in renal I/R injury is still undefined. Here, we investigated whether CHOP could regulate I/R-induced renal injury using CHOP-knockout mice and cultured renal tubular cells as models.

RESULTS

In CHOP-knockout mice, loss of renal function induced by I/R was prevented. Renal proximal tubule damage was induced by I/R in wild-type mice; however, the degree of alteration was significantly less in CHOP-knockout mice. CHOP deficiency also decreased the I/R-induced activation of caspase-3 and -8, apoptosis, and lipid peroxidation, whereas the activity of endogenous antioxidants increased. In an in vitro I/R model, small interfering RNA targeting CHOP significantly reversed increases in H2O2 formation, inflammatory signals, and apoptotic signals, while enhancing the activity of endogenous antioxidants in renal tubular cells.

INNOVATION

To the best of our knowledge, this is the first study which demonstrates that CHOP deficiency attenuates oxidative stress and I/R-induced acute renal injury both in vitro and in vivo.

CONCLUSION

These findings suggest that CHOP regulates not only apoptosis-related signaling but also ROS formation and inflammation in renal tubular cells during I/R. CHOP may play an important role in the pathophysiology of I/R-induced renal injury.

Molecular mechanism of ER stress-induced gene expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in macrophages

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor superfamily, whose members are capable of inducing apoptosis and inflammation. Endoplasmic reticulum stress (ERS) plays a key role in immune surveillance in macrophages. TRAIL mRNA and protein expression have previously been detected in macrophages; however, whether ERS has any effects on TRAIL expression in macrophages has not yet been determined. Here, we demonstrate that thapsigargin (TG) and tunicamycin (TM), two ERS inducers activated macrophages were able to increase TRAIL mRNA and protein expression in RAW264.7 macrophages, the culture supernatant of THP-1 cells, and mouse peritoneal macrophages, indicating that ERS as a potent inducer of TRAIL transcription and expression in macrophages. This effect was blocked by the specific JNK inhibitor SP600125 and transcription factor AP-1 inhibitor SR 1130. Interestingly, at the molecular level, regulation of TRAIL expression by ERS was accompanied by a significant decrease in cytokine signaling suppressor 3 (SOCS3). SOCS3 siRNA clearly increased the expression of TRAIL mRNA and protein under ERS by activating the AP-1 components phosphorylated c-Jun and phosphorylated c-Fos in RAW264.7 cells. In contrast, over-expression of SOCS3 reversed ERS-induced TRAIL expression. These findings provide in vitro evidence that SOCS3 plays a critical negative role in the regulation of ERS-induced TRAIL expression via the Jun N-terminal kinase/AP-1 signaling pathway in macrophages.

Trailing TRAIL Resistance: Novel Targets for TRAIL Sensitization in Cancer Cells

Resistance to chemotherapeutic drugs is the major hindrance in the successful cancer therapy. The tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor (TNF) family of ligands, which initiates apoptosis in cancer cells through interaction with the death receptors DR4 and DR5. TRAIL is perceived as an attractive chemotherapeutic agent as it specifically targets cancer cells while sparing the normal cells. However, TRAIL therapy has a major limitation as a large number of the cancer develop resistance toward TRAIL and escape from the destruction by the immune system. Therefore, elucidation of the molecular targets and signaling pathways responsible for TRAIL resistance is imperative for devising effective therapeutic strategies for TRAIL resistant cancers. Although, various molecular targets leading to TRAIL resistance are well-studied, recent studies have implicated that the contribution of some key cellular processes toward TRAIL resistance need to be fully elucidated. These processes primarily include aberrant protein synthesis, protein misfolding, ubiquitin regulated death receptor expression, metabolic pathways, epigenetic deregulation, and metastasis. Novel synthetic/natural compounds that could inhibit these defective cellular processes may restore the TRAIL sensitivity and combination therapies with such compounds may resensitize TRAIL resistant cancer cells toward TRAIL-induced apoptosis. In this review, we have summarized the key cellular processes associated with TRAIL resistance and their status as therapeutic targets for novel TRAIL-sensitizing agents.