DPP9 regulates NQO1 and ROS to promote resistance to chemotherapy in liver cancer cells.

Chemotherapy has been the standard treatment for liver cancer. However, intrinsic or acquired drug resistance remains a major barrier to successful treatment. At present, the underlying molecular mechanisms of chemoresistance in liver cancer have not been elucidated. Dipeptidyl peptidase 9 (DPP9) is a member of the dipeptidyl peptidase IV family that has been found to be highly expressed in a variety of tumors, including liver cancer. It is unclear whether DPP9 affects chemoresistance in liver cancer. In this study, we find that DPP9 weakens the responses of liver cancer cells to chemotherapy drugs by up-regulating NQO1 and inhibiting intracellular ROS levels. In terms of mechanism, DPP9 inhibits ubiquitin-mediated degradation of NRF2 protein by binding to KEAP1, up-regulates NRF2 protein levels, promotes mRNA transcription of NQO1, and inhibits intracellular ROS levels. In addition, the NQO1 inhibitor dicoumarol can enhance the efficacy of chemotherapy drugs in liver cancer cells. Collectively, our findings suggest that inhibiting DPP9/NQO1 signaling can serve as a potential therapeutic strategy for liver cancer.

Intercellular adhesion molecule-1 suppresses TMZ chemosensitivity in acquired TMZ-resistant gliomas by increasing assembly of ABCB1 on the membrane.

AIMS: Despite aggressive treatment, the recurrence of glioma is an inevitable occurrence, leading to unsatisfactory clinical outcomes. A plausible explanation for this phenomenon is the phenotypic alterations that glioma cells undergo aggressive therapies, such as TMZ-therapy. However, the underlying mechanisms behind these changes are not well understood. METHODS: The TMZ chemotherapy resistance model was employed to assess the expression of intercellular adhesion molecule-1 (ICAM1) in both in vitro and in vivo settings. The potential role of ICAM1 in regulating TMZ chemotherapy resistance was investigated through knockout and overexpression techniques. Furthermore, the mechanism underlying ICAM1-mediated TMZ chemotherapy resistance was examined using diverse molecular biological methods, and the lipid raft protein was subsequently isolated to investigate the cellular subcomponents where ICAM1 operates. RESULTS: Acquired TMZ resistant (TMZ-R) glioma models heightened production of intercellular adhesion molecule-1 (ICAM1) in TMZ-R glioma cells. Additionally, we observed a significant suppression of TMZ-R glioma proliferation upon inhibition of ICAM1, which was attributed to the enhanced intracellular accumulation of TMZ. Our findings provide evidence supporting the role of ICAM1, a proinflammatory marker, in promoting the expression of ABCB1 on the cell membrane of TMZ-resistant cells. We have elucidated the mechanistic pathway by which ICAM1 modulates phosphorylated moesin, leading to an increase in ABCB1 expression on the membrane. Furthermore, our research has revealed that the regulation of moesin by ICAM1 was instrumental in facilitating the assembly of ABCB1 exclusively on the lipid raft of the membrane. CONCLUSIONS: Our findings suggest that ICAM1 is an important mediator in TMZ-resistant gliomas and targeting ICAM1 may provide a new strategy for enhancing the efficacy of TMZ therapy against glioma.

ß-Lapachone, an NQO1 bioactivatable drug, prevents lung tumorigenesis in mice.

Lung cancer is one of the most lethal cancers with high incidence worldwide. The prevention of lung cancer is of great significance to reducing the social harm caused by this disease. An in-depth understanding of the molecular changes underlying precancerous lesions is essential for the targeted chemoprevention against lung cancer. Here, we discovered an increased NQO1 level over time within pulmonary premalignant lesions in both the KrasG12D-driven and nicotine-derived nitrosamine ketone (NNK)-induced mouse models of lung cancer, as well as in KrasG12D-driven and NNK-induced malignant transformed human bronchial epithelial cells (BEAS-2B and 16HBE). This suggests a potential correlation between the NQO1 expression and lung carcinogenesis. Based on this finding, we utilized ß-Lapachone (ß-Lap), an NQO1 bioactivatable drug, to suppress lung tumorigenesis. In this study, the efficacy and safety of low-dose ß-Lap were demonstrated in preventing lung tumorigenesis in vivo. In conclusion, our study suggests that long-term consumption of low-dose ß-Lap could potentially be an effective therapeutic strategy for the prevention of lung premalignant lesions. However, further studies and clinical trials are necessary to validate our findings, determine the safety of long-term ß-Lap usage in humans, and promote the use of ß-Lap in high-risk populations.

Serotonin Receptor HTR2B Facilitates Colorectal Cancer Metastasis via CREB1-ZEB1 Axis-Mediated Epithelial-Mesenchymal Transition.

A number of neurotransmitters have been detected in tumor microenvironment and proved to modulate cancer oncogenesis and progression. We previously found that biosynthesis and secretion of neurotransmitter 5-hydroxytryptamine (5-HT) was elevated in colorectal cancer cells. In this study, we discovered that the HTR2B receptor of 5-HT was highly expressed in colorectal cancer tumor tissues, which was further identified as a strong risk factor for colorectal cancer prognostic outcomes. Both pharmacological blocking and genetic knocking down HTR2B impaired migration of colorectal cancer cell, as well as the epithelial-mesenchymal transition (EMT) process. Mechanistically, HTR2B signaling induced ribosomal protein S6 kinase B1 (S6K1) activation via the Akt/mTOR pathway, which triggered cAMP-responsive element-binding protein 1 (CREB1) phosphorylation (Ser 133) and translocation into the nucleus, then the phosphorylated CREB1 acts as an activator for ZEB1 transcription after binding to CREB1 half-site (GTCA) at ZEB1 promoter. As a key regulator of EMT, ZEB1, therefore, enhances migration and EMT process in colorectal cancer cells. We also found that HTR2B-specific antagonist (RS127445) treatment significantly ameliorated metastasis and reversed EMT process in both HCT116 cell tail-vein-injected pulmonary metastasis and CT26 cell intrasplenic-injected hepatic metastasis mouse models. IMPLICATIONS: These findings uncover a novel regulatory role of HTR2B signaling on colorectal cancer metastasis, which provide experimental evidences for potential HTR2B-targeted anti-colorectal cancer metastasis therapy.

Lenvatinib Plus Camrelizumab vs. Lenvatinib Monotherapy as First-Line Treatment for Unresectable Hepatocellular Carcinoma: A Multicenter Retrospective Cohort Study.

Background: Combining an antiangiogenic agent with an anti-PD-1 agent is a promising strategy for unresectable hepatocellular carcinoma (HCC). Aims: To explore the effectiveness and tolerability of lenvatinib plus camrelizumab vs. lenvatinib monotherapy as a first-line treatment for unresectable HCC. Methods: This multicenter, retrospective cohort study included patients with unresectable HCC treated with oral lenvatinib 8 mg daily and intravenous camrelizumab 200 mg every 3 weeks (L+C group) or lenvatinib 12 mg or 8 mg daily (L group) in four Chinese centers between September 2018 and February 2020. Tumor response was evaluated according to RECIST 1.1 and mRECIST. The outcomes included objective response rate (ORR), overall survival (OS), 1-year OS rate, progression-free survival (PFS), and safety. Results: By March 31, 2021, 92 patients were finally included, with 48 and 44 in the L+C and L groups, respectively. ORR was significantly higher in the L+C group than in the L group (RECIST 1.1: 37.5% vs. 13.6%, P=0.009; mRECIST: 41.7% vs. 20.5%, P=0.029). Median OS and 95% confidence interval (CI) was 13.9 (13.3-18.3) months in the L group and not reached in the L+C group (P=0.015). The 1-year survival rate was 79.2% and 56.8% in the L+C and L groups, respectively. Median PFS was 10.3 (6.6-14.0) months and 7.5 (5.7-9.3) months in the L+C and L groups, respectively (P=0.0098). Combined therapy vs. monotherapy was independently associated with a prolonged OS (hazard ratio=0.380, 95% CI=: 0.196-0.739, P=0.004) and a prolonged PFS (hazard ratio=0.454, 95%CI=0.282-0.731, P=0.001). The safety profile was comparable between the two groups. The most common adverse event in the L+C and L groups was loss of appetite (41.7% vs. 40.9%, P=0.941). Three patients in the L+C group and two in the L group terminated treatment owing to adverse events. Conclusion: First-line lenvatinib plus camrelizumab showed better effectiveness than lenvatinib alone in patients with unresectable HCC.

Acquired temozolomide resistance in MGMTlow gliomas is associated with regulation of homologous recombination repair by ROCK2.

It was reported that MGMTlow gliomas may still be resistant to TMZ, while the mechanisms remain poorly understood. In this study, we demonstrated that rho-associated kinase 2 (ROCK2), a cytoskeleton regulator, was highly expressed in MGMTlow recurrent gliomas, and its expression strongly correlated with poor overall survival (OS) time in a subset of MGMTlow recurrent gliomas patients with TMZ therapy. And we also found that overactive ROCK2 enhanced homologous recombination repair (HR) in TMZ-resistant (TMZ-R) glioma cell lines with low MGMT expression. Silencing ROCK2 impaired HR repair, and induced double-strand break (DSB) and eradicated TMZ-R glioma cells in culture. Notably, in MGMTlow TMZ-R models, as a key factor of HR, ataxia telangiectasia-mutated (ATM) expression was upregulated directly by hyper-activation of ROCK2 to improve HR efficiency. ROCK2 enhanced the binding of transcription factor zinc finger E-box binding homeobox 1 (ZEB1) to ATM promoter for increasing ATM expression. Moreover, ROCK2 transformed ZEB1 into a gene activator via Yes-associated protein 1 (YAP1). These results provide evidence for the use of ROCK inhibitors in the clinical therapy for MGMTlow TMZ-resistant glioma. Our study also offered novel insights for improving therapeutic management of MGMTlow gliomas.

Overproduction of Gastrointestinal 5-HT Promotes Colitis-Associated Colorectal Cancer Progression via Enhancing NLRP3 Inflammasome Activation.

Chronic inflammation is a key driver for colitis-associated colorectal cancer. 5-hydroxytryptamine (5-HT), a neurotransmitter, has been reported to promote inflammation in the gastrointestinal tract. However, the mechanism behind this remains unclear. In this study, we found that 5-HT levels, as well as the expression of tryptophan hydroxylase 1 (TPH1), the 5-HT biosynthesis rate-limiting enzyme, were significantly upregulated in colorectal tumor tissues from patients with colorectal cancer, colorectal cancer mouse models, and colorectal cancer cell lines when compared with normal colorectal tissues or epithelial cell lines. Colorectal cancer cell-originated 5-HT enhanced NLRP3 inflammasome activation in THP-1 cells and immortalized bone marrow-derived macrophages (iBMDM) via its ion channel receptor, HTR3A. Mechanistically, HTR3A activation led to Ca2+ influx, followed by CaMKIIα phosphorylation (Thr286) and activation, which then induced NLRP3 phosphorylation at Ser198 (mouse: Ser194) and inflammasome assembling. The NLRP3 inflammasome mediated IL1ß maturation, and release upregulated 5-HT biosynthesis in colorectal cancer cells by inducing TPH1 transcription, revealing a positive feedback loop between 5-HT and NLRP3 signaling. Silencing TPH1 or HTR3A by short hairpin RNA slowed down tumor growth in an established CT26 and iBMDM coimplanted subcutaneous allograft colorectal cancer mouse model, whereas treatment with TPH1 inhibitor 4-chloro-DL-phenylalanine or HTR3A antagonist tropisetron alleviated tumor progression in an azoxymethane/dextran sodium sulfate-induced colorectal cancer mouse model. Addressing the positive feedback loop between 5-HT and NLRP3 signaling could provide potential therapeutic targets for colorectal cancer.

Flumethasone enhances the efficacy of chemotherapeutic drugs in lung cancer by inhibiting Nrf2 signaling pathway.

Nuclear factor erythroid-2-related factor 2 (Nrf2), a transcription factor, participates in protecting cells from electrophilic or oxidative stresses through regulating expression of cytoprotective and antioxidant genes. It has become one of the emerging targets for cancer chemosensitization, and small molecule inhibitors of Nrf2 can enhance the efficacy of chemotherapeutic drugs. Here, we found that flumethasone, a glucocorticoid, inhibited Nrf2 signaling in A549 and H460 cells by promoting Nrf2 protein degradation. Moreover, flumethasone significantly increased the sensitivity of A549 and H460 cells to chemotherapeutic drugs including cisplatin, doxorubicin and 5-FU. In mice bearing A549-shControl cells-derived xenografts, the size and weight of xenografts in the flumethasone and cisplatin combination group had a significant reduction compared with those in the cisplatin group, while in mice bearing A549-shNrf2 cells-derived xenografts, the size and weight of the xenografts in the combination group had no significant difference compared with those in the cisplatin group, demonstrating that chemosensitization effect of flumethasone is Nrf2-dependent. This work suggests that flumethasone can potentially be used as an adjuvant sensitizer to enhance the efficacy of chemotherapeutic drugs in lung cancer.

HEATR1 deficiency promotes pancreatic cancer proliferation and gemcitabine resistance by up-regulating Nrf2 signaling.

The human HEAT repeat-containing protein 1 (HEATR1), consisting of 2144 amino acids, is a member of the UTP10 family and contains one HEAT repeat at its C-terminal. HEATR1 has been reported to regulate cytotoxic T lymphocytes and rRNA synthesis, while its functions in tumors are poorly understood. Here, we found that HEATR1 competed with Keap1 for binding to p62/sequestosome 1 (SQSTM1), resulted in up-regulation of Keap1, which then inhibited Nrf2 signaling in pancreatic cancer cells. HEATR1 knockdown enhanced proliferation and gemcitabine resistance of pancreatic cancer cells. Moreover, HEATR1 deficiency significantly improved xenografts growth and led to gemcitabine resistance in pancreatic cancer cell-derived xenografts through up-regulating Nrf2 signaling. By analyzing tumor tissue samples from pancreatic cancer patients, we found that low expression of HEATR1 was closely correlated with poor prognosis and clinicopathological features. Collectively, we suggest that HEATR1 deficiency promotes proliferation and gemcitabine resistance of pancreatic cancer through up-regulating Nrf2 signaling, indicating that HEATR1 may be a promising therapeutic target for pancreatic cancer.

[Effect of anti-EGFR monoclonal antibody on chemosensitivity of human colon cancer cells and the mechanism].

OBJECTIVE: To investigate the effect of anti-EGFR monoclonal antibody on the chemosensitivity of human colon cancer cells and explore the possible molecular mechanism. METHODS: The inhibitory effect of irinotecan (CPT-11), oxaliplatin (L-OHP) and fluorouracil (5-Fu), used alone or in combination with anti-EGFR monoclonal antibody, on the proliferation of LoVo cells in vitro was assessed by MTT assay. The expressions of PI3K and Akt protein in the treated cells were examined by Western blotting, and their mRNA expressions were detected by RT-PCR. RESULTS: Both h-R3 and C-225 treatments significantly increased the chemosensitivity of LoVo cells to irinotecan and oxaliplatin. 5-Fu and h-R3 coadministered showed a synergistic effect on the cells, but 5-Fu and C-225 had an antagonistic action. Treatment with C-225 or h-R3 resulted in lowered expressions of PI3K and Akt in LoVo cells. CONCLUSION: Anti-EGFR monoclonal antibody can increase the chemosensitivity of human colon cancer cells to most chemotherapeutic drugs, and such effect might be attributed to the blocking of PI3K/Akt signaling pathway by these antibodies.

[Reversion of drug-resistant hepatocellular carcinoma cell line BEL-7402/FU by sorafenib].

AIM: To investigate the reversion of multidrug resistance of drug-resistant hepatocellular carcinoma (HCC) cell line BEL-7402/FU by sorafenib and the possible mechanisms. METHODS: Flow cytometry was applied to detect the expression of rhodamine 123 (Rho123), immunohistochemistry was applied to observe the expression of P-glycoprotein (P-gp) on the cell membrane, the fluorescence quantitative PCR assay was applied to determine the changes of the multidrug-resistant gene mdr1 mRNA level and the Western blot assay was applied to test the changes of the expression level of the mdr1 gene product P-gp. RESULTS: After 4 micromol/L treatment by sorafenib, Rho123 accumulation was increased by BEL-7402/FU and exocytosis was slowed down, which evidently reduced the expression of cell surface P-gp; the mdr1 mRNA level was reduced by 35.4% compared to its level prior to drug administration; the expression level of the mdr1 gene product P-gp was significantly suppressed, 14.3% fewer than that of BEL-7402/FU cells. CONCLUSION: Sorafenib can inhibit the expression of the mdr1 gene product P-gp and increase the intracellular concentration of chemotherapeutic drugs, so as to reverse the multidrug resistance of HCC cells.

[Clinical significance of VEGF levels in serums of colorectal cancer patients at stage IV].

OBJECTIVE: To investigate the clinical significance of vascular endothelial growth factor (VEGF) levels in serums of colorectal cancer patients at stage IV. METHODS: Using enzyme linked immunosorbent assay (ELISA) to detect the VEGF levels in serums of 45 colorectal cancer patients at stage IV, and 20 healthy served as normal control. RESULTS: The mean concentration of VEGF in 45 colorectal cancer patients at the 7 day after operation were significantly lower than that before operation (P<0.01). The mean concentration of VEGF in the patients who benefit from bevacizumab showed no statistical difference from the levels of who did not benefit (P=0.554). CONCLUSION: The VEGF levels in colorectal patients at stage IV are lowed as the load of tumor decrease. The circulating levels of VEGF seem not predict the response to bevacizumab in colorectal cancer patients at stage IV.