Targeting autophagy augments the activity of DHA-E3 to overcome p-gp mediated multi-drug resistance

Autophagy-induced intracellular signaling fractional nano-drug system for synergistic anti-tumor therapy

Autophagy inducers increase the sensitivity of tumor cells to chemotherapeutic drugs and enhance anti-tumor efficacy. An autophagy-induced intracellular signaling fractional nano-drug system was constructed for the co-delivery of the autophagy inducer rapamycin (RAPA) and the anti-tumor drug 9-nitro-20(S)-camptothecin (9-NC). Link peptides, including cathepsin B-sensitive peptides (Ala-Leu-Ala-Leu, ALAL), nucleus-targeting peptides (TAT, sequence: YGRKKRRQRRR), and chrysin (CHR)-modified hydrophobic biodegradable polymers (poly(-caprolactone)) (PCL), were grafted onto hyaluronic acid (HA) to yield two amphiphiles, HA-ALAL-PCL-CHR (CPAH) and HA-ALAL-TAT-PCL-CHR (CPTAH). Spherical RAPA- and 9-NC-loaded micelles were obtained by the self-assembly of amphiphiles comprising CPAH and RAPA and CPTAH and 9-NC. In this fractional nano-drug system, RAPA was released earlier than 9-NC, as CPAH as a RAPA carrier lacked a nucleus-targeting TAT (unlike CPTAH as an 9-NC carrier). RAPA induced autophagy in tumor cells and improved their sensitivity, whereas the secondary nucleus-targeting micelles directly delivered 9-NC to the nucleus, considerably improving anti-tumor efficacy. Immunofluorescence staining, acridine orange (AO) staining, and western blotting results demonstrated that the system induced a high level of autophagy in combination chemotherapy. The proposed system possesses a high level of cytotoxicity in vitro and in vivo and provides a potential method for enhancing anti-tumor efficacy in clinical settings.

Nitidine Chloride Triggers Autophagy and Apoptosis of Ovarian Cancer Cells through Akt/mTOR Signaling Pathway

OBJECTIVE

Ovarian cancer (OC) is the eighth most common cancer with high mortality in women worldwide. Currently, compounds derived from Chinese herbal medicine have provided a new angle for OC treatment.

METHODS

In this study, the cell proliferation and migration of ovarian cancer A2780/SKOV3 cells were inhibited after being treated with nitidine chloride (NC) by using MTT and Wound-Healing Assay. Flow cytometry analysis indicated NC-induced apoptosis of ovarian cancer cells, and AO and MDC staining showed that NC treatment induced the appearance of autophagosomes and autophagic lysosomes in ovarian cancer cells.

RESULTS

Through the autophagy inhibition experiment of chloroquine, it was proved that NC significantly further promoted apoptosis in ovarian cancer cells. Furthermore, NC proved that it could significantly decrease the expression of autophagy-related genes such as Akt, mTOR, P85 S6K, P70 S6K, and 4E-BP1.

CONCLUSION

Therefore, we suggest that NC could trigger autophagy and apoptosis of ovarian cancer cells through Akt/mTOR signaling pathway, and NC may potentially be a target for chemotherapy against ovarian cancer.

The effects and mechanisms of aloe-emodin on reversing adriamycin-induced resistance of MCF-7/ADR cells

Multidrug resistance (MDR) is one of the major obstacles for clinical effective chemotherapy. In this study, the effects and possible mechanisms of aloe-emodin (AE) were investigated on reversing the adriamycin (ADR)-induced resistance of MCF-7/ADR cells. AE could significantly reverse the ADR resistance in MCF-7/ADR cells. The combination of AE (20 μM) and ADR had no effect on the P-glycoprotein (P-gp) level, but notably promoted the accumulation of ADR in drug-resistant cells. The efflux function of P-gp required ATP, but AE reduced the intracellular ATP level. AE played a reversal role might through inhibiting the efflux function of P-gp. The research result of energy metabolism pathways indicated that combination of AE and ADR could inhibit glycolysis, tricarboxylic acid (TCA) cycle, glutamine metabolism, and related amino acid synthesis pathways. Moreover, we found AE not only reversed ADR-induced resistant but also induced autophagy as a defense mechanism. In addition, the combination of AE and ADR arrested G2/M cell cycle and induced apoptosis through DNA damage, ROS generation, caspase-3 activation. Our study indicated that AE could be a potential reversal agent to resensitize ADR resistant in tumor chemotherapy and inhibiting autophagy might be an effective strategy to further enhance the reversal activity of AE.

Long noncoding RNA ARSR is associated with a poor prognosis in patients with colorectal cancer

BACKGROUND

As one of the leading cancer-related mortalities worldwide, colorectal cancer (CRC) shows resistance to chemotherapy mainly because of drug resistance. Existing evidence has revealed that long noncoding RNAs (lncRNAs) are related to tumorigenesis and chemoresistance scenarios. However, the mechanism by which lncRNA induces chemoresistance and the postoperative prognosis of CRC both remain unclear.

METHODS

The expression of a lncRNA named lncARSR in CRC tissue was tested, and its association with clinical and pathological features was analyzed. Gain-of-function and loss-of-function assays were conducted to investigate the role of lncARSR in vivo and in vitro.

RESULTS

Functional analysis showed that overexpressing lncARSR increased oxaliplatin (OXA) resistance of CRC cells in vitro and in vivo. Moreover, lncARSR conferred chemoresistance to CRC cells. Silencing lncARSR decreased cell viability and promoted cell apoptosis after OXA treatment, whereas overexpression of lncARSR increased cell viability and reduced cell apoptosis after OXA treatment. In addition, lncARSR overexpression induced the tumor formation capacity of colorectal cancer cells.

CONCLUSIONS

The results obtained in the present study show that up-regulation of lncARSR promoted OXA resistance in CRC. Our results also imply that lncARSR may be a candidate marker for CRC chemoresistance.

Inhibition of autophagy improves resistance and enhances sensitivity of gastric cancer cells to cisplatin

Autophagy plays critical roles in tumorigenesis, while the effects of autophagy on chemoresistance of cancer cells had great disparity. This study aims to explore the impacts of autophagy on the sensitivity and resistance of gastric cancer cells to cisplatin (DDP). We firstly demonstrated that there was stronger autophagy activity in gastric cancer SGC-7901 cells than that in DDP-resisting SGC-7901/DDP cells. Then, we discovered that inhibiting autophagy by chloroquine (CQ) significantly enhanced the proliferation-inhibiting and apoptosis-inducing effects of DDP to SGC-7901 and SGC-7901/DDP cells. Moreover, CQ could partially reverse the resistance of SGC-7901/DDP cells to DDP in a concentration-dependent manner. However, the autophagy inducer everolimus (RAD001) had no obvious effects on the sensitivity of gastric cells to DDP. Mechanistically, we demonstrated that CQ might enhance the sensitivity of SGC-7901cells and improve the resistance of SGC-7901/DDP cells to DDP through inhibiting the mTORC1 pathway, especially to SGC-7901/DDP cells. Additionally, we found interfering Beclin-1 using Beclin-1 shRNA also enhanced the proliferation-inhibiting and apoptosis-inducing effects of DDP on gastric cancer cells by inhibiting phosphorylation of Akt. Our study shows that inhibiting autophagy could improve the chemoresistance and enhanced sensitivity of gastric cancer cells to DDP and provide a rationale for the administration of cisplatin combined with CQ for treating patients with gastric cancer.

Downregulation of GATS gene inhibits proliferation, clonogenicity and migration in triple negative breast cancer cells MDA-MB-231 by cell autophagy

The triple negative breast cancer (TNBC) accounts for 15% to 20% of the total number of breast cancer diagnosed. A number of clinical studies have shown that TNBC has a high risk of early recurrence and distant metastasis, and a low rate of disease free survival and total survival. The premise of TNBC deterioration was abnormal proliferation and migration of tumor cells, and this study firstly showed that GATS gene could promote proliferation of MDA-MB-231 breast cancer cells. Through lentiviral expression system, the GATS gene was konckdown by shGATS lentivirus infection in the MDA-MB-231 cells, and the result indicated it could remarkably decrease the ability of cell proliferation and migration. Real-time PCR, western blot and immunofluorescence experiments showed the expressions of protein LC3, and p-Akt in shGATS cell group were lower than the shCtrl group. Therefore, we suggest the GATS could promote the MDA-MB-231 cell proliferation, migration and clonogenicity through cell autophagy by the PI3K/Akt pathway, which paved the way for further study the function of GATS in TNBC, and GATS may potentially be a target for gene therapy against triple negative breast cancer.

Long Noncoding RNA lncARSR Promotes Doxorubicin Resistance in Hepatocellular Carcinoma via Modulating PTEN-PI3K/Akt Pathway

Hepatocellular carcinoma (HCC) is generally resistant to chemotherapy due to intrinsic or acquired drug resistances. Many molecules and signaling pathways are involved in chemo-resistance of HCC cells. However, the contribution of long noncoding RNA (lncRNA) to chemo-resistance of HCC cells is still largely unknown. In this study, we revealed the critical roles of long noncoding RNA lncARSR in chemo-resistance of HCC cells. lncARSR is upregulated in HCC, associated with large tumor size and advanced BCLC stage, and indicts poor prognosis. Functional assays showed that overexpression of lncARSR enhances doxorubicin resistance of HCC cells in vitro and in vivo. And while knockdown of lncARSR increases sensitivity of HCC cells to doxorubicin in vitro and in vivo. Mechanistically, we found that lncARSR physically associates with PTEN mRNA, promotes PTEN mRNA degradation, decreases PTEN expression, and activates PI3K/Akt pathway. PTEN is downregulated in HCC, and the expression of PTEN is negatively correlated with lncARSR in HCC tissues. Furthermore, the effects of lncARSR overexpression on doxorubicin resistance could be reversed by PI3K/Akt pathway inhibitor, and lncARSR knockdown-induced doxorubicin sensitivity could be reversed by PTEN depletion. Taken together, our results showed that upregulated lncARSR promotes doxorubicin resistance in HCC via modulating PTEN-PI3K/Akt pathway, and implied that lncARSR may serve as a promising prognostic biomarker and therapeutic target for HCC chemo-resistance. J. Cell. Biochem. 118: 4498-4507, 2017. © 2017 Wiley Periodicals, Inc.

RITA plus 3-MA overcomes chemoresistance of head and neck cancer cells via dual inhibition of autophagy and antioxidant systems

Reactivation of p53 and induction of tumor cell apoptosis (RITA) is a small molecule that blocks p53–MDM2 interaction, thereby reactivating p53 in tumors. RITA can induce exclusive apoptosis in cancer cells independently of the p53 pathway; however, the resistance of cancer cells remains a major drawback. Here, we found a novel resistance mechanism of RITA treatment and an effective combined treatment to overcome RITA resistance in head and neck cancer (HNC) cells. The effects of RITA and 3-methyladenine (3-MA) were tested in different HNC cell lines, including cisplatin-resistant and acquired RITA-resistant HNC cells. The effects of each drug alone and in combination were assessed by measuring cell viability, apoptosis, cell cycle, glutathione, reactive oxygen species, protein expression, genetic inhibition of p62 and Nrf2, and a mouse xenograft model of cisplatin-resistant HNC. RITA induced apoptosis of HNC cells at different levels without significantly inhibiting normal cell viability. Following RITA treatment, RITA-resistant HNC cells exhibited a sustained expression of other autophagy-related proteins, overexpressed p62, and displayed activation of the Keap1-Nrf2 antioxidant pathway. The autophagy inhibitor 3-MA sensitized resistant HNC cells to RITA treatment via the dual inhibition of molecules related to the autophagy and antioxidant systems. Silencing of the p62 gene augmented the combined effects. The effective antitumor activity of RITA plus 3-MA was also confirmed in vivo in mouse xenograft models transplanted with resistant HNC cells, showing increased oxidative stress and DNA damage. The results indicate that RITA plus 3-MA can help overcome RITA resistance in HNC cells.

Condensed abstract

This study revealed a novel RITA resistant mechanism associated with the sustained induction of autophagy, p62 overexpression, and Keap1-Nrf2 antioxidant system activation. The combined treatment of RITA with the autophagy inhibitor 3-methyladenine overcomes RITA resistance via dual inhibition of autophagy and antioxidant systems in vitro and in vivo.

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RITA induces apoptosis of HNC cells at different levels.

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RITA resistance is related to the sustained expression of autophagy proteins and p62.

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Keap1-Nrf2 antioxidant system is also engaged in the RITA resistance mechanism.

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The autophagy inhibitor 3-MA sensitizes resistant HNC cells to RITA treatment.

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RITA plus 3-MA induces apoptosis of resistant HNC cells via dual inhibition of autophagy and Nrf2 system in vitro and in vivo.