GM-CSF mediates immune evasion via upregulation of PD-L1 expression in extranodal natural killer/T cell lymphoma.

BACKGROUND: Granulocyte-macrophage colony stimulating factor (GM-CSF) is a cytokine that is used as an immunopotentiator for anti-tumor therapies in recent years. We found that some of the extranodal natural killer/T cell lymphoma (ENKTL) patients with the treatment of hGM-CSF rapidly experienced disease progression, but the underlying mechanisms remain to be elucidated. Here, we aimed to explore the mechanisms of disease progression triggered by GM-CSF in ENKTL. METHODS: The mouse models bearing EL4 cell tumors were established to investigate the effects of GM-CSF on tumor growth and T cell infiltration and function. Human ENKTL cell lines including NK-YS, SNK-6, and SNT-8 were used to explore the expression of programmed death-ligand 1 (PD-L1) induced by GM-CSF. To further study the mechanisms of disease progression of ENKTL in detail, the mutations and gene expression profile were examined by next-generation sequence (NGS) in the ENKTL patient's tumor tissue samples. RESULTS: The mouse-bearing EL4 cell tumor exhibited a faster tumor growth rate and poorer survival in the treatment with GM-CSF alone than in treatment with IgG or the combination of GM-CSF and PD-1 antibody. The PD-L1 expression at mRNA and protein levels was significantly increased in ENKTL cells treated with GM-CSF. STAT5A high-frequency mutation including p.R131G, p.D475N, p.F706fs, p.V707E, and p.S710F was found in 12 ENKTL cases with baseline tissue samples. Importantly, STAT5A-V706fs mutation tumor cells exhibited increased activation of STAT5A pathway and PD-L1 overexpression in the presence of GM-CSF. CONCLUSIONS: These findings demonstrate that GM-CSF potentially triggers the loss of tumor immune surveillance in ENKTL patients and promotes disease progression, which is associated with STAT5 mutations and JAK2 hyperphosphorylation and then upregulates the expression of PD-L1. These may provide new concepts for GM-CSF application and new strategies for the treatment of ENKTL.

Tea polyphenol EGCG inhibited colorectal-cancer-cell proliferation and migration via downregulation of STAT3.

BACKGROUND: Green tea is a popular beverage worldwide and epigallocatechin-3-gallate (EGCG) is the most bioactive polyphenol in green tea. Our study aims to investigate the anti-proliferation and anti-migration effects of EGCG against colorectal-cancer SW480, SW620, and LS411N cells, and elucidate the underlying mechanism. METHODS: The in vitro anti-proliferation and anti-migration effects of EGCG against colon-cancer cells were evaluated using MTT, scratch-wound-healing, and transwell-migration assays. The effects of EGCG on apoptosis were assessed by Annexin V-FITC/PI double staining and JC-1 staining. Besides, Western blotting was employed to detect the protein-expression level and elucidate the underlying pathways. Real-time qPCR and dual-luciferase reporter assay were adopted to determine the mRNA level and promoter activity. RESULTS: Our results demonstrated that treatment with EGCG resulted in significant inhibition of cell proliferation by the induction of apoptosis. EGCG also inhibited SW480 cell migration in a dose-dependent manner as assessed by wound-healing and transwell-migration assays. Western blot confirmed that EGCG induced apoptosis by the activation of Caspase-3 and PARP. In addition, both STAT3 and phosphorylated STAT3 (p-STAT3) were downregulated significantly by EGCG in three selected colorectal-cancer cell lines. EGCG treatment also resulted in a significant decrease in Bcl-2, MCL-1, and Vimentin, and an increase in E-cadherin. When STAT3 was inhibited, EGCG showed no obvious effect on cell proliferation and migration. Further investigation by luciferase-reporter-activity assay showed that EGCG suppressed the promoter activity of STAT3 and downregulated the transcription of STAT3. CONCLUSION: Our study presents evidence on the anti-proliferation and anti-migration effects of EGCG against colorectal-cancer SW480, SW620, and LS411N cells by downregulating the expression of STAT3 and suggests that EGCG could be an effective and natural supplement for colon-cancer treatment.

PBA2, a novel compound, enhances radiosensitivity in various carcinoma cells by activating the p53 pathway in vitro and in vivo.

Radiotherapy is the main method used to treat human carcinoma; however, certain types of carcinomas are radiation-insensitive. The present study aimed to explore whether a novel compound, PBA2, could enhance the radiosensitivity of various carcinoma cells in vitro and in vivo, and investigate its underlying mechanism. The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was used to assess the cytotoxicity of PBA2. Colony formation assays were used to observe the radiosensitivity effect of PBA2 in vitro. Cell cycle distributions and cell apoptosis were estimated using flow cytometry. Comet assays and Immunofluorescence assays were used to analyze DNA damage. The intracellular RNA was extracted and analyzed by sequencing. Western blotting was used to determine protein levels. A stable cell line with TP53 (encoding p53) knockdown was constructed by cell transfection. A mouse xenograft model was used to assess the radiosensitivity effect of PBA2 in vivo. We found that PBA2 at a low concentration (0.1 µM) enhanced radiosensitivity in various carcinoma cells, including CNE1, MG63, KB, HEP2, GLC82, and SMMC7221, in vitro. Combined with PBA2, radiation induced significant cell apoptosis in CNE1 and MG63 cells, accompanied by increased DNA damage, but did not affect cell cycle arrest. Mechanistically, PBA2 promoted p53 expression significantly; however, when p53 was mutated, functionally impaired, or knocked down, PBA2 could not enhance the radiosensitivity of these cells. Additionally, the combination of PBA2 and radiation reduced the tumor volume and tumor weight in CNE1 xenograft models significantly, without obvious toxicities. Our results demonstrated that PBA2 enhanced the radiosensitivity of various carcinoma cells in vitro and in vivo. The underlying mechanism might involve increasing DNA damage and cell apoptosis via activating the p53 pathway.

PD-1/PD-L1 Based Combinational Cancer Therapy: Icing on the Cake.

Cancer has been a major global health problem due to its high morbidity and mortality. While many chemotherapy agents have been studied and applied in clinical trials or in clinic, their application is limited due to its toxic side effects and poor tolerability. Monoclonal antibodies specific to the PD-1 and PD-L1 immune checkpoints have been approved for the treatment of various tumors. However, the application of PD-1/PD-L1 inhibitors remains suboptimal and thus another strategy comes in to our sight involving the combination of checkpoint inhibitors with other agents, enhancing the therapeutic efficacy. Various novel promising approaches are now in clinical trials, just as icing on the cake. This review summarizes relevant investigations on combinatorial therapeutics based on PD-1/PD-L1 inhibition.

Niclosamide, an antihelmintic drug, enhances efficacy of PD-1/PD-L1 immune checkpoint blockade in non-small cell lung cancer.

BACKGROUND: PD-1/PD-L1 blockade has received approval for clinical application due to its encouraging benefit with improving prognosis in selected populations. Unfortunately, the response to immunotherapy for many patients remains unsatisfactory. It remains a great challenge to generate potential combinations that will outperform single agents alone with regard to anti-tumor activity. METHODS: Using NSCLC cell lines and mouse models, we explored the effects of combined niclosamide and PD-L1 blockade on tumor growth and T cell function. Furthermore, we investigated the relationship between PD-L1 and p-STAT3 expression in tumor samples from patients with NSCLC using IHC, as well as their relationship to patient survival. RESULTS: In vitro, niclosamide, an antihelmintic drug, enhanced the cancer cell lysis mediated by T cells in the presence of PD-L1 blockade. Accordingly, mice treated with niclosamide and PD-L1 antibody showed significant delay in tumor growth and increased survival which were associated with the increase of tumor infiltrating T cells and granzyme B release. Importantly, we found niclosamide could decrease the expression of PD-L1 in both a concentration- and time-dependent manner in NSCLC cells, which was linked to the blockage of p-STAT3 binding to the promoter of PD-L1. CONCLUSIONS: An enhancement of PD-L1 antibody by niclosamide was observed in inhibition of NSCLC growth in vitro and in vivo, which was involved in blockage of p-STAT3 binding to promoter of PD-L1 and finally downregulation of PD-L1 expression. These encourage the combination therapy of niclosamide and PD-1/PD-L1 blockade to be further studied in clinic.

Prognostic value of gross tumor regression and plasma Epstein Barr Virus DNA levels at the end of intensity-modulated radiation therapy in patients with nasopharyngeal carcinoma.

PURPOSE: To assess gross tumor regression and plasma Epstein-Barr virus (EBV)-DNA levels at the end of intensity-modulated radiation therapy (IMRT) and its prognostic impact on patients with nasopharyngeal carcinoma (NPC). PARTICIPANTS AND METHODS: In total, 397 patients with non-metastatic, histologically confirmed NPC were retrospectively examined. All patients underwent magnetic resonance imaging of the nasopharynx and neck, and plasma EBV DNA assays before treatment and at the end of IMRT. RESULTS: The estimated 5-year loco-regional, local and regional relapse-free survival rates for patients with complete response (CR) and non-CR of the total tumor, primary tumor and metastatic lymph nodes at the end of IMRT were 94.9% vs. 85.8%, 96.6% vs. 87.3%, and 98.7% vs. 89.8%, respectively (P < 0.05). The estimated 5-year loco-regional relapse-free survival (LRRFS) rates for patients with persistent tumor with and without boost irradiation were 95.3% vs. 83%, respectively (P = 0.034). The estimated 5-year overall survival (OS), failure-free survival (FFS) and distant metastasis-free survival (DMFS) rates for patients with negative and positive plasma EBV DNA at the end of IMRT were 83.1% vs. 50.3%, 81.5% vs. 49.3%, and 87.6% vs. 61.5%, respectively (P < 0.001). Multivariate analyses indicated that regression of the total tumor and boost irradiation was an independent predictor of LRRFS, and plasma EBV DNA levels were independent predictors of OS, FFS and DMFS. CONCLUSIONS: Gross tumor regression and plasma EBV DNA levels at the end of IMRT served as predictors of poor prognosis for patients with NPC. The patients with persistent tumor and/or positive plasma EBV DNA might require timely strengthening treatment.

SOD1 Phosphorylation by mTORC1 Couples Nutrient Sensing and Redox Regulation.

Nutrients are not only organic compounds fueling bioenergetics and biosynthesis, but also key chemical signals controlling growth and metabolism. Nutrients enormously impact the production of reactive oxygen species (ROS), which play essential roles in normal physiology and diseases. How nutrient signaling is integrated with redox regulation is an interesting, but not fully understood, question. Herein, we report that superoxide dismutase 1 (SOD1) is a conserved component of the mechanistic target of rapamycin complex 1 (mTORC1) nutrient signaling. mTORC1 regulates SOD1 activity through reversible phosphorylation at S39 in yeast and T40 in humans in response to nutrients, which moderates ROS level and prevents oxidative DNA damage. We further show that SOD1 activation enhances cancer cell survival and tumor formation in the ischemic tumor microenvironment and protects against the chemotherapeutic agent cisplatin. Collectively, these findings identify a conserved mechanism by which eukaryotes dynamically regulate redox homeostasis in response to changing nutrient conditions.

Loss of MED12 Induces Tumor Dormancy in Human Epithelial Ovarian Cancer via Downregulation of EGFR.

A high rate of disease relapse makes epithelial ovarian cancer (EOC) the leading cause of death among all gynecologic malignancies. These relapses are often due to tumor dormancy. Here we identify the RNA polymerase II transcriptional mediator subunit 12 (MED12) as an important molecular regulator of tumor dormancy. MED12 knockout (KO) induced dormancy of EOC cells in vitro and in vivo, and microarray analysis showed that MED12 KO decreased expression of EGFR. Restoration of EGFR expression in MED12 KO cells restored proliferation. Additionally, MED12 bound to the promoter of EGFR, and correlation studies showed that MED12 expression positively correlated with EGFR expression in EOC patient samples. Clinical data demonstrated that chemotherapy-resistant patients expressed lower levels of MED12 compared with responsive patients. Overall, our data show that MED12 plays an important role in regulating dormancy of EOC through regulation of EGFR.Significance: MED12 is identified as a novel, important regulator of tumor dormancy in human ovarian cancer. Cancer Res; 78(13); 3532-43. ©2018 AACR.

Selective inhibitory effects of zinc on cell proliferation in esophageal squamous cell carcinoma through Orai1.

Zinc, an essential micronutrient, has a cancer preventive role. Zinc deficiency has been shown to contribute to the progression of esophageal cancer. Orai1, a store-operated Ca2+ entry (SOCE) channel, was previously reported to be highly expressed in tumor tissues removed from patients with esophageal squamous cell carcinoma (ESCC) with poor prognosis, and elevation of its expression contributes to both hyperactive intracellular Ca2+ oscillations and fast cell proliferation in human ESCC cells. However, the molecular basis of cancer preventive functions of zinc and its association with Orai1-mediated cell proliferation remains unknown. The present study shows that zinc supplementation significantly inhibits proliferation of ESCC cell lines and that the effect of zinc is reversible with N,N,N',N'-tetrakis (2-pyridylmethyl) ethylenediamine, a specific Zn2+ chelator, whereas nontumorigenic esophageal epithelial cells are significantly less sensitive to zinc treatment. Fluorescence live cell imaging revealed that extracellular Zn2+ exerted rapid inhibitory effects on Orai1-mediated SOCE and on intracellular Ca2+ oscillations in the ESCC cells. Knockdown of Orai1 or expression of Orai1 mutants with compromised zinc binding significantly diminished sensitivity of the cancer cells to zinc treatment in both SOCE and cell proliferation analyses. These data suggest that zinc may inhibit cell proliferation of esophageal cancer cells through Orai1-mediated intracellular Ca2+ oscillations and reveal a possible molecular basis for zinc-induced cancer prevention and Orai1-SOCE signaling pathway in cancer cells.-Choi, S., Cui, C., Luo, Y., Kim, S.-H., Ko, J.-K., Huo, X., Ma, J., Fu, L.-W., Souza, R. F., Korichneva, I., Pan, Z. Selective inhibitory effects of zinc on cell proliferation in esophageal squamous cell carcinoma through Orai1.

CUDC-907, a dual HDAC and PI3K inhibitor, reverses platinum drug resistance.

Platinum (Pt)-based anticancer drugs are the mainstay of treatment for solid cancers. However, resistance to Pt drugs develops rapidly, which can be caused by overexpression of multidrug resistance transporters and activation of DNA repair. CUDC-907 is a potent molecular targeted anticancer agent, rationally designed to simultaneously inhibit histone deacetylase (HDAC) and phosphatidylinositol 3-kinase (PI3K). We investigated the potentiation effect of CUDC-907 on Pt drugs in resistant cancer cells. ABCC2 stably-transfected HEK293 cells and two pairs of parental and Pt-resistant cancer cell lines were used to test for the circumvention of resistance by CUDC-907. Chemosensitivity was assessed by the sulphorhodamine B assay. Drug combinations were evaluated by the median effect analysis. ABCC2 transport activity was examined by flow cytometric assay. Cellular Pt drug accumulation and DNA platination were detected by inductively coupled plasma optical emission spectroscopy. ABCC2, ERCC1 and p21 expression were evaluated by quantitative real-time PCR. Cell cycle analysis and apoptosis assay were performed by standard flow cytometric method. The combination of CUDC-907 with cisplatin were found to exhibit synergistic cytotoxic effect in cisplatin-resistant cancer cells. In Pt-resistant cancer cells, CUDC-907 apparently circumvented the resistance through inhibition of ABCC2 and DNA repair but induction of cell cycle arrest. In the presence of CUDC-907, cellular accumulation of Pt drugs and formation of DNA-Pt adducts were found to be increased whereas expression levels of ABCC2 and ERCC1 was inhibited in Pt-resistant cells. The data advocates further development of CUDC-907 as a resistance reversal agent for use in combination cancer chemotherapy.

Survival and Toxicities of IMRT Based on the RTOG Protocols in Patients with Nasopharyngeal Carcinoma from the Endemic Regions of China.

Background: This study evaluated the survival outcomes and toxicities of intensity-modulated radiation therapy (IMRT) based on the RTOG 0225/0615 RT protocols in patients with nasopharyngeal carcinoma (NPC) from a region of China where this tumor type is endemic. Methods: A total of 455 patients with non-metastatic, histologically-confirmed NPC were retrospectively reviewed. All patients were treated by IMRT using the RTOG 0225/0615 RT protocols; 91.1% (288/316) of patients with stage III-IVb NPC received concurrent chemotherapy +/- induction chemotherapy or adjuvant chemotherapy. Results: Estimated four-year overall survival (OS), failure free survival (FFS), local relapse free survival (LRFS), regional relapse free survival (RRFS) and distant metastasis free survival (DMFS) were 83.8%, 80.5%, 94.3%, 96.7% and 85.8%, respectively. T and N category were significant prognostic factors for OS, FFS, RRFS and DMFS; and T category, for LRFS. In-field failure was the major loco-regional failure pattern. During RT, 206 (45.3%) patients experienced acute grade 3-4 toxicities. The most common acute toxicity was mucositis; 124 (27.2%) patients experienced grade 3-4 mucositis; 46 (10.1%) experienced serious late toxicities. The most common late toxicity was MRI-detected radiation-induced temporal lobe necrosis (6.8%). Conclusions: The RTOG IMRT protocols are feasible for patients with NPC from the endemic regions of China.

Prognostic value of total tumor volume in patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy.

BACKGROUND: Few studies have evaluated the prognostic value of total tumor volume (TTV), which reflects both the primary tumor volume and nodal tumor volume, in NPC. Furthermore, the relationship between TTV and survival remains unknown. The purpose of this study was to evaluate the prognostic value of TTV in patients with NPC treated with intensity-modulated radiation therapy (IMRT). METHODS: TTV was retrospectively assessed in 455 patients with newly diagnosed, non-metastatic NPC. All patients were treated using IMRT; 91.1% (288/316) of patients with stage III-IVb also received cisplatin-based chemotherapy. Receiver operating characteristic (ROC) curves were used to identify the optimal TTV cut-off point and examine the prognostic value of combined TTV with current clinical stage. RESULTS: Mean TTV was 11.1 cm3 (range, 0.3-27.9 cm3) in stage I, 22.5 cm3 (1.3-92.4 cm3) in stage II, 40.6 cm3 in stage III (3.2-129.2 cm3), and 77.5 cm3 in stage IVa-b (7.1-284.1 cm3). For all patients, the 4-year estimated FFS, OS, DMFS, and LRRFS rates for patients with a TTV ≤ 28 vs. > 28 cm3 were 93 vs. 71.4% (P < 0.001), 95.1 vs. 75.4% (P < 0.001), 94.5 vs. 79.4% (P < 0.001), and 96.2 vs. 88% (P = 0.001). TTV was an independent prognostic factor for FFS, OS, DMFS and LRRFS in all patients. In stage III-IVb, 4-year estimated FFS, OS, DMFS, and LRRFS for a TTV ≤28 vs. >28 cm3 were 88.9 vs. 70.5% (P = 0.001), 96.2 vs. 72.7% (P < 0.001), 91.2 vs. 78.3% (P = 0.008), and 93.8 vs. 87.6% (P = 0.063). TTV was an independent prognostic factor for FFS, OS and DMFS in stage III-IVb. Receiver operating characteristic (ROC) curve analysis curves revealed adding TTV to clinical stage had superior prognostic value for treatment failure compared to clinical stage alone (P = 0.016). CONCLUSIONS: TTV is an important prognosticator for treatment outcome and significantly improves the prognostic value of the current staging system for patients with NPC treated with IMRT.

Application of single-cell technology in cancer research.

In this review, we have outlined the application of single-cell technology in cancer research. Single-cell technology has made encouraging progress in recent years and now provides the means to detect rare cancer cells such as circulating tumor cells and cancer stem cells. We reveal how this technology has advanced the analysis of intratumor heterogeneity and tumor epigenetics, and guided individualized treatment strategies. The future prospects now are to bring single-cell technology into the clinical arena. We believe that the clinical application of single-cell technology will be beneficial in cancer diagnostics and treatment, and ultimately improve survival in cancer patients.

The BTK Inhibitor Ibrutinib (PCI-32765) Overcomes Paclitaxel Resistance in ABCB1- and ABCC10-Overexpressing Cells and Tumors.

Paclitaxel is one of the most widely used antineoplastic drugs in the clinic. Unfortunately, the occurrence of cellular resistance has limited its efficacy and application. The ATP-binding cassette subfamily B member 1 (ABCB1/P-glycoprotein) and subfamily C member 10 (ABCC10/MRP7) are the major membrane protein transporters responsible for the efflux of paclitaxel, constituting one of the most important mechanisms of paclitaxel resistance. Here, we demonstrated that the Bruton tyrosine kinase inhibitor, ibrutinib, significantly enhanced the antitumor activity of paclitaxel by antagonizing the efflux function of ABCB1 and ABCC10 in cells overexpressing these transporters. Furthermore, we demonstrated that the ABCB1 or ABCC10 protein expression was not altered after treatment with ibrutinib for up to 72 hours using Western blot analysis. However, the ATPase activity of ABCB1 was significantly stimulated by treatment with ibrutinib. Molecular docking analysis suggested the binding conformation of ibrutinib within the large cavity of the transmembrane region of ABCB1. Importantly, ibrutinib could effectively enhance paclitaxel-induced inhibition on the growth of ABCB1- and ABCC10-overexpressing tumors in nude athymic mice. These results demonstrate that the combination of ibrutinib and paclitaxel can effectively antagonize ABCB1- or ABCC10-mediated paclitaxel resistance that could be of great clinical interest. Mol Cancer Ther; 16(6); 1021-30. ©2017 AACR.

Degradation of P-glycoprotein by pristimerin contributes to overcoming ABCB1-mediated chemotherapeutic drug resistance in vitro.

ABCB1 (P-glycoprotein, ABCB1/MDR1) is one of the major members of the ABC transporters linked to MDR in cancer cells. In this study, we observed that pristimerin, a natural triterpenoid, potently decreased P-gp in a dose-dependent manner in both drug-resistant KBv200 and stable transfected HEK293/ABCB1 cell lines. Moreover, pristimerin also inhibited cell proliferation and induced apoptosis in both cell lines. Intriguingly, reverse transcription-PCR, real-time PCR and protein turn-over assay revealed that the decrease of P-gp was independent of mRNA level but primarily owing to its protein stability. Furthermore, immunofluorescence study with anti-P-gp antibody showed that pristimerin disturbed the subcellular distribution of P-gp with decreased location in the plasma membrane. Taken together, these data suggest that subcellular distribution of P-gp and subsequent downregulation by pristimerin contribute to overcoming ABCB1-mediated chemotherapeutic drug resistance. Our findings suggested inducing the decrease of P-gp membrane protein could be a new promising alternative therapeutic strategy in ABCB1-mediated MDR.

Reversal of platinum drug resistance by the histone deacetylase inhibitor belinostat.

OBJECTIVES: To investigate and elucidate the mechanism for the potentiation of cisplatin anticancer activity by belinostat in platinum (Pt)-resistant lung cancer cells. MATERIALS AND METHODS: Combination of cisplatin and belinostat was investigated in two pairs of parental and cisplatin-resistant non-small cell lung cancer (NSCLC) cell lines. The Pt-resistant cell models exhibited overexpression of the efflux transporter ABCC2 and enhanced DNA repair capacity. Cellular accumulation of cisplatin and extent of DNA platination were measured by inductively coupled plasma optical emission spectrometer. Expression of Pt transporters and DNA repair gene were determined by quantitative real-time PCR. Inhibition of ABCC2 transport activity was examined by flow cytometric assay. Regulation of ABCC2 at the promoter level was studied by chromatin immunoprecipitation assay. RESULTS AND CONCLUSION: In Pt-resistant lung cancer cells, belinostat apparently circumvent the resistance through inhibition of both ABCC2 and DNA repair-mediated mechanisms. The combination of belinostat and cisplatin were found to display synergistic cytotoxic effect in cisplatin-resistant lung cancer cell lines when the two drugs were added concomitantly or when belinostat was given before cisplatin. Upon the concomitant administration of belinostat, cellular accumulation of cisplatin and formation of DNA-Pt adducts were found to be increased whereas expression levels of the efflux transporter ABCC2 and the DNA repair gene ERCC1 were inhibited in Pt-resistant cells. Belinostat-mediated downregulation of ABCC2 was associated with an increase association of a transcriptional repressor (negative cofactor 2) but reduced association of a transcriptional activator (TFIIB) to the ABCC2 promoter. The data advocates the use of belinostat as a novel drug resistance reversal agent for use in combination cancer chemotherapeutic regimens.

PBA2, a novel inhibitor of imatinib-resistant BCR-ABL T315I mutation in chronic myeloid leukemia.

Chronic Myeloid Leukemia (CML) is largely caused by the Philadelphia (Ph) chromosome carrying the Break point Cluster Region-Abelson (BCR-ABL) oncogene. Imatinib is a BCR-ABL-targeted therapy and considered the standard of care in CML management. Resistance to imatinib therapy often develops because of mutations in the BCR-ABL kinase domain. In this study, we evaluated PBA2, a novel BCR-ABL inhibitor, for its anti-cancer activity against BCR-ABL expressing BaF3 cells. PBA2 shows potent activity against wild-type and T315I mutated BaF3 cells as compared with imatinib. PBA2 inhibited the phosphorylation of BCR-ABL and its downstream signaling in BaF3/WT and BaF3/T315I cells. PBA2 inhibited the mRNA expression of BCR-ABL in BaF3/WT and BaF3/T315I cells. Mechanistically, PBA2 increased the cell population in sub G1 phase of the cell cycle, induced apoptosis and elevated ROS production in both BaF3/WT and BaF3/T315I cells. Taken together, our results indicate that PBA2 exhibits anti-proliferative effects and inhibits the imatinib-resistant T315I BCR-ABL mutation. PBA2 may be a novel drug candidate for overcoming the resistance to imatinib in CML patients.

Data showing the circumvention of oxaliplatin resistance by vatalanib in colon cancer.

We have recently reported that vatalanib, an orally active small molecule multi-tyrosine kinase inhibitor (Hess-Stumpp et al., 2005 [1]), can sensitize multidrug resistant (MDR) colon cancer cells to chemotherapy under hypoxia by inhibiting two MDR transporters ABCB1 and ABCG2 (To et al., 2015 [2]). This data article describes the possible circumvention of resistance to specifically platinum (Pt)-based anticancer drugs by vatalanib via inhibition of two other efflux transporters ABCC2 and ATP7A. Data from the flow cytometric transporter efflux assay showed specific inhibition of ABCC2 activity by vatalanib in stable transfected cells and ABCC2-overexpressing oxaliplatin-resistant colon cancer cells HCT116/Oxa. We also performed the transporter ABCC2 ATPase assay and showed an increase in ATP hydrolysis by ABCC2 in the presence of vatalanib. ATP7A mRNA expression was also shown to be upregulated in HCT116/Oxa cells. Vatalanib was shown to suppress this upregulated ATP7A expression. Data from the cellular Pt accumulation assay showed a lower Pt accumulation in HCT116/Oxa cells than the parental sensitive HCT116 cells. Vatalanib was shown to increase cellular Pt accumulation in a concentration-dependent manner. Combination of oxaliplatin and vatalanib was shown to restore the suppressed apoptosis in HCT116/Oxa cells.

Predictive Efficacy Biomarkers of Programmed Cell Death 1/Programmed Cell Death 1 Ligand Blockade Therapy.

Inhibitors of immune check-point molecule, programmed cell death 1 (PD-1) and its ligand, programmed cell death ligand 1 (PD-L1) have attracted much attention in cancer immunotherapy recently due to their durable antitumor effects in various malignances, especially the advanced ones. Unfortunately, only a fraction of patients with advanced tumors could benefit from anti-PD-1/PD-L1 therapy, while others still worsened. The key to this point is that there are no efficient biomarkers for screening anti-PD-1/PD-L1-sensitive patients. In this review, we aim at summarizing the latest advances of anti-PD-1/PDL1 immunotherapy and the potential predictive efficacy biomarkers to provide evidences for identifying anti-PD-1/PDL1- sensitive patients. The present article also includes the patent review coverage on this topic.

Vatalanib sensitizes ABCB1 and ABCG2-overexpressing multidrug resistant colon cancer cells to chemotherapy under hypoxia.

Cancer microenvironment is characterized by significantly lower oxygen concentration. This hypoxic condition is known to reduce drug responsiveness to cancer chemotherapy via multiple mechanisms, among which the upregulation of the ATP-binding cassette (ABC) efflux transporters confers resistance to a wide variety of structurally unrelated anticancer drugs. Vatalanib (PTK787/ZK22584) is a multitargeted tyrosine kinase inhibitor for all isoforms of VEGFR, PDGFR and c-Kit, which exhibit potent anticancer activity in vitro and in vivo. We investigated the potentiation effect of vatalanib on the anticancer activity of conventional cytotoxic drugs in colon cancer cell lines under both normoxic and hypoxic conditions. Mechanistically, vatalanib was found to inhibit ABCG2 and ABCB1 efflux activity, presumably by acting as a competitive inhibitor and interfering with their ATPase activity. Under hypoxic growth condition, ABCG2 and ABCB1-overexpressing cells sorted out by FACS technique as side population (SP) were found to be significantly more responsive to SN-38 (ABCG2 and ABCB1 substrate anticancer drug) in the presence of vatalanib. The anchorage independent soft agar colony formation capacity of the SP cells was remarkably reduced upon treatment with a combination of SN-38 and vatalanib, compared to SN-38 alone. However, vatalanib, at concentrations that produced the circumvention of the transporters-mediated resistance, did not appreciably alter ABCG2/ABCB1 mRNA or protein expression levels or the phosphorylation of Akt and extracellular signal-regulated kinase (ERK1/2). Our study thus advocates the further investigation of vatalanib for use in combination chemotherapy to eradicate drug-resistant cancer cells under hypoxia.