Inhibiting the Activity of ABCG2 by KU55933 in Colorectal Cancer.

BACKGROUND: Therapeutic resistance is a frequent problem of cancer treatment and a leading cause of mortality in patients with metastatic colorectal cancer (CRC). Recent insight into the mechanisms that confer multidrug resistance has elucidated that the ATP-binding cassette (ABC) superfamily G member 2 (ABCG2) assists cancer cells in escaping therapeutic stress caused by toxic chemotherapy. Therefore, it is necessary to develop ABCG2 inhibitors. OBJECTIVES: In the present study, we investigated the inhibitory effect of KU55933 on ABCG2 in CRC. METHODS: The cytotoxicity assay and drug accumulation assay were used to examine the inhibitory effect of KU55933 on ABCG2. The protein expressions were detected by Western blot assay. The docking assay was performed to predict the binding site and intermolecular interactions between KU55933 and ABCG2. RESULTS: KU55933 was more potent than the known ABCG2 inhibitor fumitremorgin C to enhance the sensitivity of mitoxantrone and doxorubicin and the intracellular accumulation of mitoxantrone, doxorubicin and rhodamine 123 inside CRC cells with ABCG2 overexpression. Moreover, KU55933 did not affect the protein level of ABCG2. Furthermore, the docking data showed that KU55933 was tightly located in the drug-binding pocket of ABCG2. CONCLUSION: In summary, our data presented that KU55933 could effectively inhibit the drug pump activity of ABCG2 in colorectal cancer, which is further supported by the predicted model that showed the hydrophobic interactions of KU55933 within the drug-binding pocket of ABCG2. KU55933 can potently inhibit the activity of ABCG2 in CRC.

AZ32 Reverses ABCG2-Mediated Multidrug Resistance in Colorectal Cancer.

Colorectal cancer is a common malignancy with the third highest incidence and second highest mortality rate among all cancers in the world. Chemotherapy resistance in colorectal cancer is an essential factor leading to the high mortality rate. The ATP-binding cassette (ABC) superfamily G member 2 (ABCG2) confers multidrug resistance (MDR) to a range of chemotherapeutic agents by decreasing their intracellular content. The development of novel ABCG2 inhibitors has emerged as a tractable strategy to circumvent drug resistance. In this study, an ABCG2-knockout colorectal cancer cell line was established to assist inhibitor screening. Additionally, we found that ataxia-telangiectasia mutated (ATM) kinase inhibitor AZ32 could sensitize ABCG2-overexpressing colorectal cancer cells to ABCG2 substrate chemotherapeutic drugs mitoxantrone and doxorubicin by retaining them inside cells. Western blot assay showed that AZ32 did not alter the expression of ABCG2. Moreover, molecule docking analysis predicted that AZ32 stably located in the transmembrane domain of ABCG2. In conclusion, our result demonstrated that AZ32 could potently reverse ABCG2-mediated MDR in colorectal cancer.

Piperlongumine Alleviates Mouse Colitis and Colitis-Associated Colorectal Cancer.

Colorectal cancer is one of the most common and lethal cancers in the world. An important causative factor of colorectal cancer is ulcerative colitis. In this study, we investigated the therapeutic effects of piperlongumine (PL) on the dextran sulfate sodium (DSS)-induced acute colitis and azoxymethane (AOM)/DSS-induced colorectal cancer mouse models. Our results showed that PL could inhibit the inflammation of DSS-induced mouse colitis and reduce the number of large neoplasms (diameter >2 mm) of AOM/DSS-induced mouse colorectal cancer by downregulation of proinflammatory cytokines cyclooxygenase-2 and interleukin-6 and epithelial-mesenchymal transition-related factors, ß-catenin, and snail expressions, but fail to improve the colitis symptoms and to decrease the incidence of colonic neoplasms and the number of small neoplasms (diameter <2 mm). These data suggested that PL might be an effective agent in treating colitis and colorectal cancer.

miR-936 Suppresses Cell Proliferation, Invasion, and Drug Resistance of Laryngeal Squamous Cell Carcinoma and Targets GPR78.

MicroRNAs (miRs) play important roles in tumor progression. miR-936 has been reported to suppress cell invasion and proliferation of glioma and non-small cell lung cancer. Nevertheless, the function of miR-936 in laryngeal squamous cell carcinoma (LSCC) remains undiscovered. Hence, our study was to investigate the role of miR-936 in LSCC. In our present research, we have testified that miR-936 was substantially downregulated in LSCC tissues compared with adjacent normal tissues. Furthermore, miR-936 could inhibit proliferation, migration and invasion, and improve the sensitivity to doxorubicin and cisplatin of LSCC cells. Additionally, luciferase reporter assays were performed to confirm that GPR78 was a novel target of miR-936, and the protein expression of GPR78 was obviously inhibited by miR-936 in LSCC cells. In summary, our study indicates that the miR-936/GPR78 axis could be both a diagnostic marker and a therapeutic target for LSCC.

Survivin Promotes Piperlongumine Resistance in Ovarian Cancer.

Ovarian cancer is one of the most fatal female malignancies while targeting apoptosis is critical for improving ovarian cancer patients' lives. Survivin is regarded as the most robust anti-apoptosis protein, and its overexpression in ovarian cancer is related to poor survival and apoptosis resistance. Piperlongumine (PL) extracted from peppers is defined as an active alkaloid/amide and exhibits a broad spectrum of antitumor effects. Here, we demonstrate that PL induces the rapid depletion of survivin protein levels via reactive oxygen species (ROS)-mediated proteasome-dependent pathway in vitro, while exerting a remarkable inhibitory influence on the proliferation of ovarian cancer cells. Overexpression of survivin raises the survival rate of ovarian cancer cells to PL. Moreover, PL inhibits ovarian cancer cells xenograft tumor growth and downregulates survivin in vivo. Our findings reveal a previously unrecognized mechanism of PL in suppressing survivin expression as well as survivin promotes piperlongumine resistance in ovarian cancer and suggest that ROS-mediated proteasome-dependent pathway can be exploited to overcome apoptosis resistance triggered by aberrant expression of survivin.

Reciprocal regulation of miR-1205 and E2F1 modulates progression of laryngeal squamous cell carcinoma.

The burgeoning functions of many microRNAs (miRs) have been well study in cancer. However, the level and function of miR-1205 in laryngeal squamous cell cancer remains unknown. In the current research, we validated that miR-1205 was notably downregulated in human laryngeal squamous cell carcinoma (LSCC) samples in comparison with tissues adjacent to LSCC, and correlated with T stage, lymph node metastasis, and clinical stage. Using Kaplan-Meier analysis indicates that high expression of miR-1205 has a favorable prognosis for patients with LSCC. Functional assays show that enforced miR-1205 expression attenuates the migration, growth, and invasion of LSCC cells. And E2F1 is verified to be a target of miR-1205, while E2F1 binds to miR-1205 promoter and transcriptionally inhibits miR-1205 expression. Overexpression of E2F1 reverses the inhibitory impacts of miR-1205 on LSCC cells in part. Importantly, E2F1 is abnormally increased in LSCC tissues, and its protein levels were inversely relevant to miR-1205 expression. High E2F1 protein level is in connection with clinical stage, T stage, lymph node metastasis, and poor prognosis. Consequently, reciprocal regulation of miR-1205 and E2F1 plays a crucial role in the progression of LSCC, suggesting a new miR-1205/E2F1-based clinical application for patients of LSCC.

Targeting TF-AKT/ERK-EGFR Pathway Suppresses the Growth of Hepatocellular Carcinoma.

Tissue factor (TF) is a transmembrane glycoprotein to initiate blood coagulation and frequently overexpressed in a variety of tumors. Our previous study has showed that the expression of TF is upregulated and correlated with prognosis in hepatocellular carcinoma (HCC). However, the role and molecular mechanism of TF in the growth of HCC are still unclear. In vitro and in vivo functional experiments were performed to determine the effect of TF on the growth of HCC cells. A panel of biochemical assays was used to elucidate the underlying mechanisms. TF could promote the growth of HCC in vitro and in vivo by activating both ERK and AKT signaling pathways. TF induced EGFR upregualtion, and inhibition of EGFR suppressed TF-mediated HCC growth. In addition, TF protein expression was correlated with EGFR in HCC tissues. TF promotes HCC growth by upregulation of EGFR, and TF as well as EGFR may be potential therapeutic targets of HCC.

Targeting uPAR by CRISPR/Cas9 System Attenuates Cancer Malignancy and Multidrug Resistance.

Urokinase plasminogen activator receptor (uPAR), a member of the lymphocyte antigen 6 protein superfamily, is overexpressed in different types of cancers and plays an important role in tumorigenesis and development. In this study, we successfully targeted uPAR by CRISPR/Cas9 system in two human cancer cell lines with two individual sgRNAs. Knockout of uPAR inhibited cell proliferation, migration and invasion. Furthermore, knockout of uPAR decreases resistance to 5-FU, cisplatin, docetaxel, and doxorubicin in these cells. Although there are several limitations in the application of CRISPR/Cas9 system for cancer patients, our study offers valuable evidences for the role of uPAR in cancer malignancy and drug resistance.

Celastrol Inhibits the Growth of Ovarian Cancer Cells in vitro and in vivo.

Celastrol is a natural triterpene isolated from the Chinese plant Thunder God Vine with potent antitumor activity. However, the effect of celastrol on the growth of ovarian cancer cells in vitro and in vivo is still unclear. In this study, we found that celastrol induced cell growth inhibition, cell cycle arrest in G2/M phase and apoptosis with the increased intracellular reactive oxygen species (ROS) accumulation in ovarian cancer cells. Pretreatment with ROS scavenger N-acetyl-cysteine totally blocked the apoptosis induced by celastrol. Additionally, celastrol inhibited the growth of ovarian cancer xenografts in nude mice. Altogether, these findings suggest celastrol is a potential therapeutic agent for treating ovarian cancer.

Erastin Reverses ABCB1-Mediated Docetaxel Resistance in Ovarian Cancer.

Overexpression of drug efflux transport ABCB1 is correlated with multidrug resistance (MDR) among cancer cells. Upregulation of ABCB1 accounts for the recurrence of resistance to docetaxel therapy in ovarian cancer with poor survival. Erastin is a novel and specific small molecule that targets SLC7A11 to induce ferroptosis. In the present research, we explored the synergistic effect of erastin and docetaxel in ovarian cancer. We confirmed that the co-delivery of erastin with docetaxel significantly decreased cell viability, promoted cell apoptosis, and induced cell cycle arrest at G2/M in ovarian cancer cells with ABCB1 overexpression. Mechanistically, erastin dominantly elevated the intracellular ABCB1 substrate levels by restricting the drug-efflux activity of ABCB1 without alteration of the expression of ABCB1. Consequently, erastin can reverse ABCB1-mediated docetaxel resistance in ovarian cancer, revealing that the combination of erastin and docetaxel may potentially offer an effective administration for chemo-resistant patients suffering from ovarian cancers.

Inhibition of WEE1 Suppresses the Tumor Growth in Laryngeal Squamous Cell Carcinoma.

WEE1 is a tyrosine kinase that regulates G2/M cell cycle checkpoint and frequently overexpressed in various tumors. However, the expression and clinical significance of WEE1 in human laryngeal squamous cell carcinoma (LSCC) are still unknown. In this study, we found that WEE1 was highly expressed in LSCC tissues compared with adjacent normal tissues. Importantly, overexpression of WEE1 was correlated with T stages, lymph node metastasis, clinical stages and poor prognosis of LSCC patients. Furthermore, inhibition of WEE1 by MK-1775 induced cell growth inhibition, cell cycle arrest and apoptosis with the increased intracellular reactive oxygen species (ROS) levels in LSCC cells. Pretreatment with ROS scavenger N-acetyl-L-cysteine could reverse MK-1775-induced ROS accumulation and cell apoptosis in LSCC cells. MK-1775 also inhibited the growth of LSCC xenografts in nude mice. Altogether, these findings suggest that WEE1 is a potential therapeutic target in LSCC, and inhibition of WEE1 is the prospective strategy for LSCC therapy.

YM155 enhances docetaxel efficacy in ovarian cancer.

YM155 (Sepantronium bromide) is a potent small molecule inhibitor of survivin by suppression of survivin expression and shows the promising anticancer activity in many types of cancers. Docetaxel (Taxotere®) is a member of the taxane drugs used in the treatment of a number of cancers in clinic. Despite the therapeutic efficacy of docetaxel is encouraging, the emergent resistance is an urgent issue. In this study, we investigate the effect of YM155 on docetaxel efficacy in ovarian cancer cells. Our data showed that YM155 actively induced cell growth inhibition, cell cycle arrest and apoptosis with downregualtion of survivin in ovarian cancer cells. Moreover, YM155 increased the intracellular ROS levels, and pretreatment with either NAC or GSH partially reversed the YM155-induced ROS accumulation and apoptosis only in the parental A2780 cells, but not in the resistant A2780/Taxol cells. Furthermore, YM155 enhanced docetaxel efficacy to inhibit the growth and induce apoptosis in ovarian cancer cells. Take together, our results suggested that combination of YM155 and docetaxel may be a feasible strategy for the treatment of ovarian cancer.

Cyclin-dependent kinase 7 inhibitor THZ2 inhibits the growth of human gastric cancer in vitro and in vivo.

Cyclin-dependent kinase 7 (CDK7) is a member of the CDK family, which forms the CDK activating kinase complex with Cyclin H and RING finger protein Mat1 to control cell cycle progression and transcription by phosphorylating other CDKs and RNA polymerase II. In this study, we analyzed TCGA data and found that upregulation of CDK7 frequently occurred in human gastric cancer. A potent and selective irreversible CDK7 inhibitor THZ2 was able to induce cell growth inhibition, cell cycle arrest at G2/M phase and apoptosis with the increasing intracellular reactive oxidative species (ROS) levels in gastric cancer cells. Pretreatment with ROS scavenger N-acety-L-cysteine partially reversed cell apoptosis induced by THZ2. In the nude mice, THZ2 also suppressed the growth of xenograft tumors of gastric cancer. Overall, our data showed that inhibition of CDK7 with THZ2 in gastric cancer presented outstanding anticancer effect in vitro and in vivo, suggesting that CDK7 is a potential therapeutic target for gastric cancer patients.

Oxymatrine and Cisplatin Synergistically Enhance Anti-tumor Immunity of CD8+ T Cells in Non-small Cell Lung Cancer.

Oxymatrine (OMT) has shown broad antitumor activities for the treatment of several types of cancers. However, little is known about its effect on anti-tumor immunity. Combination therapy is a potentially promising strategy of cancer to enhance anticancer activity, overcome drug resistance, and lower treatment failure rate. In the present study, we demonstrated that the combination of OMT with cisplatin (DDP) synergistically inhibited non-small cell lung cancer (NSCLC) cells growth when co-cultured with peripheral blood mononuclear cells in vitro. Furthermore, the combination of OMT with DDP significantly inhibited the growth of Lewis lung cancer (LLC) mouse xenograft tumors. Flow cytometry analysis revealed that OMT and DDP synergistically increase the CD8+/ regulatory T cells ratio and enhanced more CD8+ T cells secreted cytokines of IFN-γ, TNF-α, and IL-2 in vivo. Mechanistically, upregulation of miR-155 and downregulation of suppressor of cytokine signaling-1 (SOCS1) were confirmed as a target signaling pathway to positively regulate the anti-tumor response of CD8+ T cells. Overall, OMT in combination with DDP showed outstanding synergistic anti-tumor immunity, suggesting that this beneficial combination may offer a potential immunotherapy for NSCLC patients.