BI-2865, a pan-KRAS inhibitor, reverses the P-glycoprotein induced multidrug resistance in vitro and in vivo.

BACKGROUND: Multidrug resistance (MDR) limits successful cancer chemotherapy. P-glycoprotein (P-gp), BCRP and MRP1 are the key triggers of MDR. Unfortunately, no MDR modulator was approved by FDA to date. Here, we will investigate the effect of BI-2865, a pan-KRAS inhibitor, on reversing MDR induced by P-gp, BCRP and MRP1 in vitro and in vivo, and its reversal mechanisms will be explored. METHODS: The cytotoxicity of BI-2865 and its MDR removal effect in vitro were tested by MTT assays, and the corresponding reversal function in vivo was assessed through the P-gp mediated KBv200 xenografts in mice. BI-2865 induced alterations of drug discharge and reservation in cells were estimated by experiments of Flow cytometry with fluorescent doxorubicin, and the chemo-drug accumulation in xenografts' tumor were analyzed through LC-MS. Mechanisms of BI-2865 inhibiting P-gp substrate's efflux were analyzed through the vanadate-sensitive ATPase assay, [125I]-IAAP-photolabeling assay and computer molecular docking. The effects of BI-2865 on P-gp expression and KRAS-downstream signaling were detected via Western blotting, Flow cytometry and/or qRT-PCR. Subcellular localization of P-gp was visualized by Immunofluorescence. RESULTS: We found BI-2865 notably fortified response of P-gp-driven MDR cancer cells to the administration of chemo-drugs including paclitaxel, vincristine and doxorubicin, while such an effect was not observed in their parental sensitive cells and BCRP or MRP1-driven MDR cells. Importantly, the mice vivo combination study has verified that BI-2865 effectively improved the anti-tumor action of paclitaxel without toxic injury. In mechanism, BI-2865 prompted doxorubicin accumulating in carcinoma cells by directly blocking the efflux function of P-gp, which more specifically, was achieved by BI-2865 competitively binding to the drug-binding sites of P-gp. What's more, at the effective MDR reversal concentrations, BI-2865 neither varied the expression and location of P-gp nor reduced its downstream AKT or ERK1/2 signaling activity. CONCLUSIONS: This study uncovered a new application of BI-2865 as a MDR modulator, which might be used to effectively, safely and specifically improve chemotherapeutic efficacy in the clinical P-gp mediated MDR refractory cancers.

ABC transporters affects tumor immune microenvironment to regulate cancer immunotherapy and multidrug resistance.

Multidrug resistance (MDR) is the phenomenon in which cancer cells simultaneously develop resistance to a broad spectrum of structurally and mechanistically unrelated drugs. MDR severely hinders the effective treatment of cancer and is the major cause of chemotherapy failure. ATP-binding cassette (ABC) transporters are extensively expressed in various body tissues, and actively transport endogenous and exogenous substrates through biological membranes. Overexpression of ABC transporters is frequently observed in MDR cancer cells, which promotes efflux of chemotherapeutic drugs and reduces their intracellular accumulation. Increasing evidence suggests that ABC transporters regulate tumor immune microenvironment (TIME) by transporting various cytokines, thus controlling anti-tumor immunity and sensitivity to anticancer drugs. On the other hand, the expression of various ABC transporters is regulated by cytokines and other immune signaling molecules. Targeted inhibition of ABC transporter expression or function can enhance the efficacy of immune checkpoint inhibitors by promoting anticancer immune microenvironment. This review provides an update on the recent research progress in this field.

Lactobacillus gallinarum-derived metabolites boost anti-PD1 efficacy in colorectal cancer by inhibiting regulatory T cells through modulating IDO1/Kyn/AHR axis.

OBJECTIVE: Gut microbiota is a key player in dictating immunotherapy response. We aimed to explore the immunomodulatory effect of probiotic Lactobacillus gallinarum and its role in improving anti-programmed cell death protein 1 (PD1) efficacy against colorectal cancer (CRC). DESIGN: The effects of L. gallinarum in anti-PD1 response were assessed in syngeneic mouse models and azoxymethane/dextran sulfate sodium-induced CRC model. The change of immune landscape was identified by multicolour flow cytometry and validated by immunohistochemistry staining and in vitro functional assays. Liquid chromatography-mass spectrometry was performed to identify the functional metabolites. RESULTS: L. gallinarum significantly improved anti-PD1 efficacy in two syngeneic mouse models with different microsatellite instability (MSI) statuses (MSI-high for MC38, MSI-low for CT26). Such effect was confirmed in CRC tumourigenesis model. L. gallinarum synergised with anti-PD1 therapy by reducing Foxp3+ CD25+ regulatory T cell (Treg) intratumoural infiltration, and enhancing effector function of CD8+ T cells. L. gallinarum-derived indole-3-carboxylic acid (ICA) was identified as the functional metabolite. Mechanistically, ICA inhibited indoleamine 2,3-dioxygenase (IDO1) expression, therefore suppressing kynurenine (Kyn) production in tumours. ICA also competed with Kyn for binding site on aryl hydrocarbon receptor (AHR) and antagonised Kyn binding on CD4+ T cells, thereby inhibiting Treg differentiation in vitro. ICA phenocopied L. gallinarum effect and significantly improved anti-PD1 efficacy in vivo, which could be reversed by Kyn supplementation. CONCLUSION: L. gallinarum-derived ICA improved anti-PD1 efficacy in CRC through suppressing CD4+Treg differentiation and enhancing CD8+T cell function by modulating the IDO1/Kyn/AHR axis. L. gallinarum is a potential adjuvant to augment anti-PD1 efficacy against CRC.

PCI29732, a Bruton's Tyrosine Kinase Inhibitor, Enhanced the Efficacy of Conventional Chemotherapeutic Agents in ABCG2-Overexpressing Cancer Cells.

BACKGROUND/AIMS: Multidrug resistance (MDR) induced by the ABC transporter subfamily B member 1 (ABCB1) and subfamilyG member 2 (ABCG2) limits successful cancer chemotherapy and no commercially available MDR modulator is used in the clinic. In the current study, we aimed to investigate the effects of PCI29732 on the enhancement of chemotherapeutic agents. METHODS: Cell cytotoxicity and reversal effect were measured with MTT assay. Additionally, flow cytometry was employed to detect the accumulation and efflux of the drugs. We investigated the interaction of PCI29732 and the substrate binding sites of ABCG2 was investigated via the photo-labeling of ABCG2 with the [125I] iodoarylazidoprazosin. The vanadate-sensitive ATPase activity of ABCG2 was measured to identify whether the drug affected the ATPase activity. RT-PCR and Western blot were utilized to analyze mRNA and protein expression respectively. RESULTS: Here, we found that PCI29732 significantly enhanced the efficacy of substrate chemotherapeutic agents in ABCG2-overexpressing cells and also in xenografts harboring the H460/MX20 cell that overexpress ABCG2, but not in their parental sensitive cells and ABCB1-overexpressing cells. Mechanistically, the intracellular accumulations of doxorubicin and Rhodamine 123 were increased in ABCG2-overexpressing S1-MI-80 cells with the presence of PCI29732. PCI29732 stimulated the ATPase activity of ABCG2 at low concentrations. However at the high concentrations, PCI29732 inhibited the ATPase activity, and competed with [125I]-iodoarylazidoprazosin for photo-affinity labeling of ABCG2. PCI29732 did neither alter the mRNA or protein expression levels of ABCG2 nor the phosphorylation levels of AKT and ERK1/2. CONCLUSION: Our study demonstrates that PCI29732 inhibits the function of ABCG2 by competitively binding to the ATP-binding site of ABCG2 and enhances the anti-tumor efficacy of substrate chemotherapeutic agents, This findings encourages the development of combinational chemotherapy for the treatment of ABCG2- overexpressing cancer patients.

Polyoxypregnane steroids from the stems of Marsdenia tenacissima.

A new polyoxypregnane aglycone, tenacigenin D (1), and seven new C21 steroid glycosides, tenacissimosides D-J (2-8), were isolated from the stems of Marsdenia tenacissima. Their structures were determined by interpretation of their 1D and 2D NMR and other spectroscopic data, as well as by comparison with published values for related known compounds. Compound 1 was found to circumvent P-glycoprotein (P-gp)-mediated multidrug resistance through an inhibitory effect on P-gp with a similar potency to verapamil. In addition, compound 1 potentiated the activity of erlotinib and gefitinib in epidermal growth factor receptor tyrosine kinase inhibitor (EGFR TKI)-resistant non-small-cell lung cancer cells.

Small-molecule agents for cancer immunotherapy.

Cancer immunotherapy, exemplified by the remarkable clinical benefits of the immune checkpoint blockade and chimeric antigen receptor T-cell therapy, is revolutionizing cancer therapy. They induce long-term tumor regression and overall survival benefit in many types of cancer. With the advances in our knowledge about the tumor immune microenvironment, remarkable progress has been made in the development of small-molecule drugs for immunotherapy. Small molecules targeting PRR-associated pathways, immune checkpoints, oncogenic signaling, metabolic pathways, cytokine/chemokine signaling, and immune-related kinases have been extensively investigated. Monotherapy of small-molecule immunotherapeutic drugs and their combinations with other antitumor modalities are under active clinical investigations to overcome immune tolerance and circumvent immune checkpoint inhibitor resistance. Here, we review the latest development of small-molecule agents for cancer immunotherapy by targeting defined pathways and highlighting their progress in recent clinical investigations.

Antitumor effects of novel compound, guttiferone K, on colon cancer by p21Waf1/Cip1-mediated G(0) /G(1) cell cycle arrest and apoptosis.

Low selectivity is one of the major problems of currently used anticancer drugs, therefore, there is a high demand for novel, selective antitumor agents. In this study, the anticancer effects and mechanisms of guttiferone K (GUTK), a novel polyprenylated acylphloroglucinol derivative isolated from Garcinia cowa Roxb., were examined for its development as a novel drug targeting colon cancer. GUTK concentration- and time-dependently reduced the viability of human colon cancer HT-29 cells (IC(50) value 5.39 ± 0.22 µM) without affecting the viability of normal human colon epithelial CCD 841 CoN cells and induced G(0) /G(1) cell cycle arrest in HT-29 cells by down-regulating cyclins D1, D3 and cyclin-dependent kinases 4 and 6, while selectively restoring p21Waf1/Cip1 and p27Kip1 to levels comparable to those observed in normal colon cells, without affecting their levels in normal cells. GUTK (10.0 µM) induced cleavage of PARP, caspases-3, -8 and -9 and chromatin condensation to stimulate caspase-3-mediated apoptosis. The addition of a JNK inhibitor, SP600125, partially reversed GUTK-induced caspase-3 activity, indicating the possible involvement of JNK in GUTK-induced apoptosis. Furthermore, GUTK (10 mg/kg, i.p.) significantly decreased the tumor volume in a syngeneic colon tumor model when used alone or in combination with 5-fluorouracil without toxicity to the mice. Immunohistochemical staining of the tumor sections revealed a mechanism involving an increase in cleaved caspase-3 and a decrease in cell proliferation marker Ki-67. Our results support GUTK as a promising novel, potent and selective antitumor drug candidate for colon cancer.

Association of markers of inflammation on attention and neurobehavioral outcomes in survivors of childhood acute lymphoblastic leukemia.

Background: Survivors of childhood acute lymphoblastic leukemia (ALL) are at-risk of developing cognitive impairment and neurobehavioral symptoms. Inflammation induced by a compromised health status during cancer survivorship is proposed as a pathophysiological mechanism underlying cognitive impairment in cancer survivors. Objectives: To evaluate the associations of biomarkers of inflammation with attention and neurobehavioral outcomes in survivors of childhood ALL, and to identify clinical factors associated with biomarkers of inflammation in this cohort. Methods: We recruited patients who were diagnosed with ALL at ≤ 18 years old and were currently ≥5 years post-cancer diagnosis. The study outcomes were attention (Conners Continuous Performance Test) and self-reported behavioral symptoms (Adult Self-Report [ASR] checklist). Using a commercial screening kit, survivors' plasma (5ml) was assayed for 17 cytokines/chemokine cell-signaling molecules that are associated with neurodegenerative diseases. The final panel of the targeted markers included interleukin (IL)-8, IL-13, interferon-gamma (IFN-γ), monocyte chemoattractant protein-1 (MCP-1), macrophage inflammatory protein-1ß, and tumor necrosis factor-α. Biomarker levels were rank-ordered into tertiles based on the sample distribution. Multivariable general linear modeling was used to test for associations between biomarkers and study outcomes in the overall cohort and stratified by gender. Results: This study included 102 survivors (55.9% males, mean[SD] age 26.2[5.9] years; 19.3[7.1] years post-diagnosis). Survivors within top tertiles of IFN-γ (Estimate =6.74, SE=2.26; P=0.0037) and IL-13 (Estimate =5.10, SE=2.27; P=0.027) demonstrated more inattentiveness. Adjusting for age, gender and treatment, more self-reported thought (Estimate=3.53, SE=1.78; P=0.050) and internalizing problems (Estimate =6.52, SE=2.91; P=0.027) correlated with higher IL-8. Higher levels of IL-13 (RR = 4.58, 95% CI: 1.01-11.10) and TNF-α (RR = 1.44, 95% CI: 1.03-4.07) were observed in survivors had developed chronic health conditions (n=26, 25.5%). The stratified analysis showed that association of IFN-γ with attention was stronger in male survivors than in female survivors. Conclusion: Inflammation due to cancer-related late effects may potentially be mechanistic mediators of neurobehavioral problems in pediatric ALL survivors. Markers of inflammation can potentially be applied to assess or monitor the effectiveness of interventions, particularly behavioral interventions, in improving cognitive outcomes in survivors. Future work includes understanding the underlying gender-specific pathophysiology behind functional outcomes in the population.

A20 promotes colorectal cancer immune evasion by upregulating STC1 expression to block "eat-me" signal.

Immune checkpoint inhibitors (ICIs) have induced durable clinical responses in a subset of patients with colorectal cancer (CRC). However, the dis-satisfactory response rate and the lack of appropriate biomarkers for selecting suitable patients to be treated with ICIs pose a major challenge to current immunotherapies. Inflammation-related molecule A20 is closely related to cancer immune response, but the effect of A20 on "eat-me" signal and immunotherapy efficacy remains elusive. We found that A20 downregulation prominently improved the antitumor immune response and the efficacy of PD-1 inhibitor in CRC in vitro and in vivo. Higher A20 expression was associated with less infiltration of immune cells including CD3 (+), CD8 (+) T cells and macrophages in CRC tissues and also poorer prognosis. Gain- and loss-A20 functional studies proved that A20 could decrease the "eat-me" signal calreticulin (CRT) protein on cell membrane translocation via upregulating stanniocalcin 1 (STC1), binding to CRT and detaining in mitochondria. Mechanistically, A20 inhibited GSK3ß phosphorylating STC1 at Thr86 to slow down the degradation of STC1 protein. Our findings reveal a new crosstalk between inflammatory molecule A20 and "eat-me" signal in CRC, which may represent a novel predictive biomarker for selecting CRC patients most likely to benefit from ICI therapy.

Axitinib targeted cancer stemlike cells to enhance efficacy of chemotherapeutic drugs via inhibiting the drug transport function of ABCG2.

Stemlike cells have been isolated by their ability to efflux Hoechst 33342 dye and are called the side population (SP). We evaluated the effect of axitinib on targeting cancer stemlike cells and enhancing the efficacy of chemotherapeutical agents. We found that axitinib enhanced the cytotoxicity of topotecan and mitoxantrone in SP cells sorted from human lung cancer A549 cells and increased cell apoptosis induced by chemotherapeutical agents. Moreover, axitinib particularly inhibited the function of adenosine triphosphate (ATP)-binding cassette subfamily G member 2 (ABCG2) and reversed ABCG2-mediated multidrug resistance (MDR) in vitro. However, no significant reversal effect was observed in ABCB1-, ABCC1- or lung resistance-related protein (LRP)-mediated MDR. Furthermore, in both sensitive and MDR cancer cells axitinib neither altered the expression of ABCG2 at the mRNA or protein levels nor blocked the phosphorylation of AKT and extracellular signal-regulated kinase (ERK)1/2. In nude mice bearing ABCG2-overexpressing S1-M1-80 xenografts, axitinib significantly enhanced the antitumor activity of topotecan without causing additional toxicity. Taken together, these data suggest that axitinib particularly targets cancer stemlike cells and reverses ABCG2-mediated drug resistance by inhibiting the transporter activity of ABCG2.

Disease Status-Dependent Drug-Herb Interactions: NASH Lowered the Risk of Hepatotoxicity in Rats Coadministered With Simvastatin and Gardenia jasminoides J. Ellis.

Concurrent use of simvastatin (SV) and Gardenia jasminoides J. Ellis (GJ) was adopted in patients with multi-morbidity, such as stroke rehabilitation patients with NASH. Although hepatotoxicity has been reported in both of them and NASH could alter the pharmacokinetics of drugs/herbs, the interaction between SV and GJ and the related hepatotoxicity remained uninvestigated under neither healthy nor NASH condition. The current study aimed to evaluate the potential hepatotoxicity resulted from the interactions between SV and GJ in both healthy and NASH rats. Both healthy and NASH rats received two-week SV (p. o., 8.66 mg/kg, once daily) and/or GJ (p.o., 325 mg/kg, twice daily). Pharmacokinetic profiles of SV, simvastatin acid (SVA, active metabolite of SV), and geniposide (major component in GJ); hepatic Cyp2c11/Oatp1b2/P-gp expression; and biomarker levels of liver function, lipid levels, and liver histology were compared to demonstrate the interactions in rats. To explore the mechanism of the interaction-mediated hepatotoxicity, hepatic genipin-protein adduct content and iNOS/COX-1/COX-2 expressions from related groups were compared. Moreover, liver histology of healthy/NASH rats at 90 days after discontinuation of two-week GJ in the absence and presence of SV was evaluated to estimate the long-term impact of the interactions. GJ reduced the systemic exposures of SV and SVA by up-regulating the hepatic P-gp expression in healthy but not NASH rats. Meanwhile, SV increased the systemic exposure of geniposide via inhibiting the activity of P-gp in both healthy and NASH rats. Although neither SV nor GJ induced hepatotoxicity in healthy rats, their co-treatment elevated serum ALT and AST levels, which may attribute to the aggravated genipin-protein adduct formation, inflammation infiltration, and iNOS/COX-1 expressions in the liver. In NASH rats, SV and/or GJ reduced serum ALT, AST, LDL/vLDL, and TC levels via alleviating hepatic inflammation infiltration and iNOS/COX-1 expressions. Moreover, in comparison to NASH rats, more severe fibrosis was observed in the livers of healthy rats at 90 days after discontinuation of two-week SV and GJ coadministration. Although interactions between SV and GJ induced short-term and long-term liver injuries in healthy rats, NASH condition in rats could lower such risk.

Formulation strategies for bacteriophages to target intracellular bacterial pathogens.

Bacteriophages (Phages) are antibacterial viruses that are unaffected by antibiotic drug resistance. Many Phase I and Phase II phage therapy clinical trials have shown acceptable safety profiles. However, none of the completed trials could yield data supporting the promising observations noted in the experimental phage therapy. These trials have mainly focused on phage suspensions without enough attention paid to the stability of phage during processing, storage, and administration. This is important because in vivo studies have shown that the effectiveness of phage therapy greatly depends on the ratio of phage to bacterial concentrations (multiplicity of infection) at the infection site. Additionally, bacteria can evade phages through the development of phage-resistance and intracellular residence. This review focuses on the use of phage therapy against bacteria that survive within the intracellular niches. Recent research on phage behavior reveals that some phage can directly interact with, get internalized into, and get transcytosed across mammalian cells, prompting further research on the governing mechanisms of these interactions and the feasibility of harnessing therapeutic phage to target intracellular bacteria. Advances to improve the capability of phage attacking intracellular bacteria using formulation approaches such as encapsulating/conjugating phages into/with vector carriers via liposomes, polymeric particles, inorganic nanoparticles, and cell penetrating peptides, are summarized. While promising progress has been achieved, research in this area is still in its infancy and warrants further attention.

Polyoxypregnanes as safe, potent, and specific ABCB1-inhibitory pro-drugs to overcome multidrug resistance in cancer chemotherapy in vitro and in vivo.

Multidrug resistance (MDR) mediated by ATP binding cassette subfamily B member 1 (ABCB1) is significantly hindering effective cancer chemotherapy. However, currently, no ABCB1-inhibitory drugs have been approved to treat MDR cancer clinically, mainly due to the inhibitor specificity, toxicity, and drug interactions. Here, we reported that three polyoxypregnanes (POPs) as the most abundant constituents of Marsdenia tenacissima (M. tenacissima) were novel ABCB1-modulatory pro-drugs, which underwent intestinal microbiota-mediated biotransformation in vivo to generate active metabolites. The metabolites at non-toxic concentrations restored chemosensitivity in ABCB1-overexpressing cancer cells via inhibiting ABCB1 efflux activity without changing ABCB1 protein expression, which were further identified as specific non-competitive inhibitors of ABCB1 showing multiple binding sites within ABCB1 drug cavity. These POPs did not exhibit ABCB1/drug metabolizing enzymes interplay, and their repeated administration generated predictable pharmacokinetic interaction with paclitaxel without obvious toxicity in vivo. We further showed that these POPs enhanced the accumulation of paclitaxel in tumors and overcame ABCB1-mediated chemoresistance. The results suggested that these POPs had the potential to be developed as safe, potent, and specific pro-drugs to reverse ABCB1-mediated MDR. Our work also provided scientific evidence for the use of M. tenacissima in combinational chemotherapy.

Intestinal absorption and hepatic elimination of drugs in high-fat high-cholesterol diet-induced non-alcoholic steatohepatitis rats: exemplified by simvastatin.

BACKGROUND AND PURPOSE: Altered drug pharmacokinetics is a significant concern in non-alcoholic steatohepatitis (NASH) patients. Although high-fat high-cholesterol (HFHC) diet-induced NASH (HFHC-NASH) rats could simulate the typical dysregulation of cholesterol in NASH patients, experimental investigation on the altered drug pharmacokinetics in this model are limited. Thus, the present study comprehensive investigates the nature of such altered pharmacokinetics using simvastatin as the model drug. EXPERIMENTAL APPROACH: Pharmacokinetic profiles of simvastatin and its active metabolite simvastatin acid together with compartmental pharmacokinetic modelling were used to identify the key factors involved in the altered pharmacokinetics of simvastatin in HFHC-NASH rats. Experimental investigations via in situ single-pass intestinal perfusion and intrahepatic injection of simvastatin were carried out. Histology, Ces1 activities and mRNA/protein levels of Oatp1b2/CYP2c11/P-gp in the small intestine/liver of healthy and HFHC-NASH rats were compared. KEY RESULTS: Reduced intestinal absorption and more extensive hepatic elimination in HFHC-NASH rats resulted in less systemic exposures of simvastatin/simvastatin acid. In the small intestine of HFHC-NASH rats, thicker intestinal wall with more collagen fibres, increased Ces1 activity and up-regulated P-gp protein decreased the permeability of simvastatin, accelerated the hydrolysis of simvastatin and promoted the efflux of simvastatin acid respectively. In the liver of HFHC-NASH rats, higher hepatic P-gp expression accelerated the hepatic elimination of simvastatin. CONCLUSION AND IMPLICATIONS: Altered histology, Ces1 activity and P-gp expression in the small intestine/liver were identified to be the major contributing factors leading to less systemic exposure of drugs in HFHC-NASH rats, which may be applicable to NASH patients.

Anticancer effect and structure-activity analysis of marine products isolated from metabolites of mangrove fungi in the South China Sea.

Marine-derived fungi provide plenty of structurally unique and biologically active secondary metabolites. We screened 87 marine products from mangrove fungi in the South China Sea for anticancer activity by MTT assay. 14% of the compounds (11/86) exhibited a potent activity against cancer in vitro. Importantly, some compounds such as compounds 78 and 81 appeared to be promising for treating cancer patients with multidrug resistance, which should encourage more efforts to isolate promising candidates for further development as clinically useful chemotherapeutic drugs. Furthermore, DNA intercalation was not involved in their anticancer activities, as determined by DNA binding assay. On the other hand, the structure-activity analysis indicated that the hydroxyl group was important for their cytotoxic activity and that bulky functional groups such as phenyl rings could result in a loss of biological activity, which will direct the further development of marine product-based derivatives.

Anthracenedione derivatives as anticancer agents isolated from secondary metabolites of the mangrove endophytic fungi.

In this article, we report anticancer activity of 14 anthracenedione derivatives separated from the secondary metabolites of the mangrove endophytic fungi Halorosellinia sp. (No. 1403) and Guignardia sp. (No. 4382). Some of them inhibited potently the growth of KB and KBv200 cells, among which compound 6 displayed strong cytotoxicity with IC(50) values of 3.17 and 3.21 microM to KB and KBv200 cells, respectively. Furthermore, we demonstrate that the mechanism involved in the apoptosis induced by compound 6 is probably related to mitochondrial dysfunction. Additionally, the structure-activity relationships of these compounds are discussed.

Correction: Alectinib (CH5424802) antagonizes ABCB1- and ABCG2-mediated multidrug resistance in vitro, in vivo and ex vivo.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

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.

New Pt-NNSO core anticancer agents: Structural optimization and investigation of their anticancer activity.

A series of new platinum Pt(II) compounds possessing a bidentate leaving ligand modified from oxaliplatin has been synthesized, with one of the oxygen ligating atom substituted for a sulphur atom (resulting in a Pt-NNSO coordination core structure). The general structures are R,R-diaminocyclohexane (DACH)-Pt-(methylthio)acetic acid (K4) and DACH-Pt-(thiophenylacetic acid) (K4 derivatives). Substitution of an electron donating or withdrawing group at the ortho or para position on the phenyl ring of K4 derivatives was found to affect the complexes' stability, reactivity with the biological molecules (5'-guanosine monophosphate (5'-GMP) and L-methionine (L-Met)) and anticancer activity. 1H NMR experiments demonstrated that Pt-NNSO complexes formed a mixture of mono- and diadduct with 5'-GMP in various ratios, which are different from the classical Pt drugs (forming mainly diadduct). In addition, all of the K4 derivatives with improved lipophilicity are less deactivated by L-Met in comparison to cisplatin (CDDP) and oxaliplatin. Biological assessments showed that all Pt-NNSO complexes are less toxic than CDDP in normal porcine kidney cells and are minimally affected by drug resistance. Some of the new compounds also displayed comparable anticancer activity to CDDP or better than carboplatin in a few cancer cell lines. The lower reactivity of the Pt-NNSO compounds than CDDP towards thiol molecules, presumably leading to less efflux in resistant cancer cells, and the ability to inhibit autophagy were believed to allow the new compounds to be less affected by Pt resistance.

Identification of Clinically Approved Drugs Indacaterol and Canagliflozin for Repurposing to Treat Epidermal Growth Factor Tyrosine Kinase Inhibitor-Resistant Lung Cancer.

In advanced lung cancer, epidermal growth factor tyrosine kinase inhibitors (EGFR TKIs) have extraordinary clinical efficacy. However, their usefulness is severely compromised by drug resistance mediated by various mechanisms, the most important of which is the secondary EGFR T790M mutation. The mutation blocks the binding of EGFR TKIs to the receptor kinase, thereby abolishing the therapeutic efficacy. In this study, we used our free and open-source protein-ligand docking software idock to screen worldwide approved small-molecule drugs against EGFR T790M. The computationally selected drug candidates were evaluated in vitro in resistant non-small cell lung cancer (NSCLC) cell lines. The specificity of the drugs toward the mutant EGFR was demonstrated by cell-free kinase inhibition assay. The inhibition of EGFR kinase activity and its downstream signaling pathways in NSCLC cells was shown by immunoblot analysis. The positive hints were revealed to be indacaterol, canagliflozin, and cis-flupenthixol, all of which were shown to induce apoptosis in NSCLC cells harboring the EGFR T790M mutation. Moreover, the combination of indacaterol with gefitinib was also found to produce synergistic anticancer effect in NSCLC cells bearing EGFR T790M. The observed synergistic effect was likely contributed by the enhanced inhibition of EGFR and its downstream signaling molecules.