OBJECTIVES: Oxaliplatin (OXA) and 5-fluorouracil (5-FU) are 2 commonly used chemotherapeutic agents for colorectal cancer (CRC). MicroRNAs (miRNAs, miRs) play crucial roles in the development of chemoresistance in various cancers. However, the role and mechanism of miR-224-5p in regulating CRC chemoresistance remain unclear. This study aims to investigate the function of miR-224-5p in chemoresistant CRC cells and the underlying mechanisms. METHODS: CRC datasets GSE28702 and GSE69657 were downloaded from the Gene Expression Omnibus (GEO) database. Differentially expressed miRNAs between drug-sensitive and resistant groups (OXA or 5-FU) were analyzed, and miR-224-5p was identified as the target miRNA. Chemoresistant cell lines HCT15-OXR, HCT15-5-FU, SW480-OXR, and SW480-5-FU were established. Transient transfections were performed using miR-224-5p mimics, inhibitors, and their respective negative controls (control mimic, control inhibitor) in these cell lines. Cells were treated with different concentrations of OXA or 5-FU post-transfection, and the half-maximal inhibitory concentration (IC₅₀) was determined using the cell counting kit-8 (CCK-8) assay. Cell proliferation was assessed by CCK-8 and colony formation assays. The expression levels of miR-224-5p, LC3, and P62 were measured by real-time polymerase chain reaction (real-time PCR) and/or Western blotting. Autophagic flux was assessed using a tandem fluorescent-tagged LC3 reporter assay. TargetScan 8.0, miRTarBase, miRPathDB, and HADb were used to predict B-cell lymphoma-2 (Bcl-2) as a potential miR-244-5p target, which was further validated by dual-luciferase reporter assays. RESULTS: Chemoresistant CRC cells exhibited down-regulated miR-224-5p expression, whereas up-regulation of miR-224-5p enhanced chemotherapy sensitivity. Exposure to OXA or 5-FU significantly increased autophagic activity in chemoresistant CRC cells, which was reversed by miR-224-5p overexpression. Dual-luciferase assays verified Bcl-2 as a direct target of miR-224-5p. CONCLUSIONS MiR-224-5p regulates chemoresistance in CRC by modulating autophagy through direct targeting of Bcl-2.
Humans ; MicroRNAs/physiology* ; Colorectal Neoplasms/drug therapy* ; Drug Resistance, Neoplasm/genetics* ; Autophagy/drug effects* ; Fluorouracil/pharmacology* ; Oxaliplatin ; Cell Line, Tumor ; Proto-Oncogene Proteins c-bcl-2/metabolism* ; Gene Expression Regulation, Neoplastic

OBJECTIVES: To investigate the role of DTX2 in regulating biological behaviors of oxaliplatin-resistant colorectal cancer cells (CRC/OXA cells). METHODS: CCK8 assay was used to determine the inhibition rate of oxaliplatin-treated CRC cells. A CRC/OXA cell line was constructed, in which DTX2 expression level was detected. The cells were transfected with a DTX2-shRNA plasmid or co-transfected with DTX2-shRNA and pcDNA-Notch2, and the changes in cell proliferation, migration and invasion ability were evaluated using plate cloning assay, scratch assay and Transwell invasion assay. The expression levels of Notch2, NICD and epithelial-mesenchymal transition (EMT) proteins of the transfected cells were detected with Western blotting. In a nude mouse model bearing SW620/OXA cell xenografts, the effects of DTX2 knockdown and Notch2 overexpression in the implanted cells on tumor growth and protein expressions were tested. RESULTS: The IC₅₀ of oxaliplatin was 6.00 μmol/L in SW620 cells and 8.00 μmol/L in LoVo cells. CRC/OXA cells showed a significantly increased expression of DTX2. DTX2 knockdown in CRC/OXA cells significantly inhibited cell proliferation, migration and invasion, and these effects were reversed by co-transfection of the cells with pcDNA-Notch2. DTX2 knockdown significantly reduced the expression levels of Notch2, NICD and vimentin proteins and increased E-cadherin expression in CRC/OXA cells, and co-transfection with pcDNA-Notch2 potently attenuated the changes in these proteins. In the tumor-bearing mice, DTX2 overexpression obviously promoted the growth of SW620/OXA cell xenograft, enhanced the protein expressions of Notch2, NICD and vimentin, and lowered the expression of E-cadherin. CONCLUSIONS High expression of DTX2 promotes proliferation, migration, invasion and EMT of CRC/OXA cells through the Notch2 signaling pathway, suggesting the potential of DTX2 as a target to improve the efficacy of oxaliplatin.
Epithelial-Mesenchymal Transition ; Humans ; Cell Proliferation ; Oxaliplatin ; Colorectal Neoplasms/metabolism* ; Animals ; Drug Resistance, Neoplasm ; Receptor, Notch2/metabolism* ; Cell Line, Tumor ; Mice, Nude ; Cell Movement ; Organoplatinum Compounds/pharmacology* ; Neoplasm Invasiveness ; Mice

Objective: To investigate the effect of rigosertib (RGS) combined with classic chemotherapy drugs including 5-fluorouracil, oxaliplatin, and irinotecan in colorectal cancer. Methods: Explore the synergy effects of RGS and 5-fluorouracil (5-FU), oxaliplatin (OXA), and irinotecan (IRI) on colorectal cancer by subcutaneously transplanted tumor models of mice. The mice were randomly divided into control group, RGS group, 5-FU group, OXA group, IRI group, 5-FU+ RGS group, OXA+ RGS group and IRI+ RGS group. The synergy effects of RGS and OXA on KRAS mutant colorectal cancer cell lines in vitro was detected by CCK-8. Ki-67 immunohistochemistry and TdT-mediated dUTP nick-end labeling (TUNEL) staining were performed on the mouse tumor tissue sections, and the extracted tumor tissue was analyzed by western blot. The blood samples of mice after chemotherapy and RGS treatment were collected, blood routine and liver and kidney function analysis were conducted, and H&E staining on liver sections was performed to observe the side effects of chemotherapy and RGS. Results: The subcutaneously transplanted tumor models were established successfully in all groups. 55 days after administration, the fold change of tumor size of OXA+ RGS group was 37.019±8.634, which is significantly smaller than 77.571±15.387 of RGS group (P=0.029) and 92.500±13.279 of OXA group (P=0.008). Immunohistochemical staining showed that the Ki-67 index of tumor tissue in control group, OXA group, RGS group and OXA+ RGS group were (100.0±16.8)%, (35.6±11.3)%, (54.5±18.1)% and (15.4±3.9)%, respectively. The Ki-67 index of OXA+ RGS group was significantly lower than that in control group (P=0.014), but there was no significant difference compared to OXA group and RGS group (OXA: P=0.549; RGS: P=0.218). TUNEL fluorescence staining showed that the apoptotic level of OXA+ RGS group was 3.878±0.547, which was significantly higher than 1.515±0.442 of OXA group (P=0.005) and 1.966±0.261 of RGS group (P=0.008). Western blot showed that the expressions of apoptosis related proteins such as cleaved-PARP, cleaved-caspase 3 and cleaved-caspase 8 in the tumor tissues of mice in the OXA+ RGS group were higher than those in control group, OXA group and RGS group. After the mice received RGS combined with chemotherapy drugs, there was no significant effect on liver and kidney function indexes, but the combined use of oxaliplatin and RGS significantly reduced the white blood cells [(0.385±0.215)×10(9)/L vs (5.598±0.605)×10(9)/L, P<0.001] and hemoglobin[(56.000±24.000)g/L vs (153.333±2.231)g/L, P=0.001] of the mice. RGS, chemotherapy combined with RGS and chemotherapy alone did not significantly increase the damage to liver cells. Conclusions: The combination of RGS and oxaliplatin has a stronger anti-tumor effect on KRAS mutant colorectal cancer. RGS single agent will not cause significant bone marrow suppression and hepatorenal injury in mice, but its side effects may increase correspondingly after combined with chemotherapy.
Animals ; Mice ; Antineoplastic Combined Chemotherapy Protocols ; Apoptosis Regulatory Proteins ; Colorectal Neoplasms/genetics* ; Fluorouracil/pharmacology* ; Irinotecan/therapeutic use* ; Ki-67 Antigen ; Oxaliplatin ; Proto-Oncogene Proteins p21(ras)/therapeutic use*

Objective: To observe the platinum drugs resistance effect of N-acetyltransferase 10 (NAT10) overexpression in breast cancer cell line and elucidate the underlining mechanisms. Methods: The experiment was divided into wild-type (MCF-7 wild-type cells without any treatment) group, NAT10 overexpression group (H-NAT10 plasmid transfected into MCF-7 cells) and NAT10 knockdown group (SH-NAT10 plasmid transfected into MCF-7 cells). The invasion was detected by Transwell array, the interaction between NAT10 and PARP1 was detected by co-immunoprecipitation. The impact of NAT10 overexpression or knockdown on the acetylation level of PARP1 and its half-life was also determined. Immunostaining and IP array were used to detect the recruitment of DNA damage repair protein by acetylated PARP1. Flow cytometry was used to detect the cell apoptosis. Results: Transwell invasion assay showed that the number of cell invasion was 483.00±46.90 in the NAT10 overexpression group, 469.00±40.50 in the NAT10 knockdown group, and 445.00±35.50 in the MCF-7 wild-type cells, and the differences were not statistically significant (P>0.05). In the presence of 10 μmol/L oxaliplatin, the number of cell invasion was 502.00±45.60 in the NAT10 overexpression group and 105.00±20.50 in the NAT10 knockdown group, both statistically significant (P<0.05) compared with 219.00±31.50 in wild-type cells. In the presence of 10 μmol/L oxaliplatin, NAT10 overexpression enhanced the binding of PARP1 to NAT10 compared with wild-type cells, whereas the use of the NAT10 inhibitor Remodelin inhibited the mutual binding of the two. Overexpression of NAT10 induced PARP1 acetylation followed by increased PARP1 binding to XRCC1, and knockdown of NAT10 expression reduced PARP1 binding to XRCC1. Overexpression of NAT10 enhanced PARP1 binding to LIG3, while knockdown of NAT10 expression decreased PARP1 binding to LIG3. In 10 μmol/L oxaliplatin-treated cells, the γH2AX expression level was 0.38±0.02 in NAT10 overexpressing cells and 1.36±0.15 in NAT10 knockdown cells, both statistically significant (P<0.05) compared with 1.00±0.00 in wild-type cells. In 10 μmol/L oxaliplatin treated cells, the apoptosis rate was (6.54±0.68)% in the NAT10 overexpression group and (12.98±2.54)% in the NAT10 knockdown group, both of which were statistically significant (P<0.05) compared with (9.67±0.37)% in wild-type cells. Conclusion: NAT10 overexpression enhances the binding of NAT10 to PARP1 and promotes the acetylation of PARP1, which in turn prolongs the half-life of PARP1, thus enhancing PARP1 recruitment of DNA damage repair related proteins to the damage sites, promoting DNA damage repair and ultimately the survival of breast cancer cells.
Breast Neoplasms/enzymology* ; Cell Line, Tumor ; Drug Resistance, Neoplasm ; Female ; Humans ; MCF-7 Cells ; N-Terminal Acetyltransferases/metabolism* ; Organoplatinum Compounds/pharmacology* ; Oxaliplatin/pharmacology* ; X-ray Repair Cross Complementing Protein 1

Oxaliplatin is a key drug in chemotherapy of colorectal cancer (CRC). However, its efficacy is unsatisfied due to drug resistance of cancer cells. In this study, we tested whether a natural agent, ursolic acid, was able to enhance the efficacy of oxaliplatin for CRC. Four CRC cell lines including SW480, SW620, LoVo, and RKO were used as in vitro models, and a SW620 xenograft mouse model was used in further in vivo study. We found that ursolic acid inhibited proliferation and induced apoptosis of all four cells and enhanced the cytotoxicity of oxaliplatin. This effect was associated with down-regulation of Bcl-xL, Bcl-2, survivin, activation of caspase-3, 8, 9, and inhibition of KRAS expression and BRAF, MEK1/2, ERK1/2, p-38, JNK, AKT, IKKα, IκBα, and p65 phosphorylation of the MAPK, PI3K/AKT, and NF-κB signaling pathways. The two agents also showed synergistic effects against tumor growth in vivo. In addition, ursolic acid restored liver function and body weight of the mice treated with oxaliplatin. Thus, we concluded that ursolic acid could enhance the therapeutic effects of oxaliplatin against CRC both in vitro and in vivo, which offers an effective strategy to minimize the burden of oxaliplatin-induced adverse events and provides the groundwork for a new clinical strategy to treat CRC.
Animals ; Antineoplastic Combined Chemotherapy Protocols ; pharmacology ; Cell Line, Tumor ; Colorectal Neoplasms ; drug therapy ; metabolism ; pathology ; Drug Synergism ; Female ; Humans ; Mice ; Mice, Nude ; Neoplasm Proteins ; metabolism ; Organoplatinum Compounds ; agonists ; pharmacology ; Oxaliplatin ; Triterpenes ; agonists ; pharmacology ; Xenograft Model Antitumor Assays