Analysis of the correlation between circular RNA circ_0008274 and cetuximab resistance in colorectal cancer cells / 中华消化杂志

ABSTRACT

Objective:To analyze the expression of circular RNA circ_0008274 in cetuximab-resistant colorectal cancer cells using bioinformatics technology and to explore its involvement in the development of cetuximab resistance.Methods:Five concentrations of cetuximab (10, 50, 100, 150, 200 nmol/L) were set. Cetuximab-resistant cells DiFi-R and Caco-2-R were screened out and established by concentration increasing method using colorectal cancer cells DiFi and Caco-2. The expression of circ_0008274 in DiFi-R and Caco-2-R cells was detected by reverse transcription-polymerase chain reaction(RT-PCR). The interaction and regulation between circ_0008274 and microRNA(miR)-140-3p were analyzed by double-luciferase reporter assay. The highly expressed gene SMARCC1 related to cetuximab resistance was determined by Western blotting. Circ_0008274 in DiFi-R and Caco-2-R cells were knocked out with small interfering RNA si-circ_0008274 transfection. After knock out, the differences in the colony formation and cell proliferation in DiFi-R and Caco-2-R cells were compared. MiR-140-3p mimic and blank control miR were transfected into DiFi-R and Caco-2-R cells. After transfection the difference in cell proliferation between transfected with miR-140-3p mimic and blank control miR in DiFi-R and Caco-2-R cells were analyzed. After Caco-2-R cell was knocked out with si-circ_0008274, the changes of SMARCC1 protein expression rescued by pcDNA3.1 SMARCC1 and cell viability were analyzed. The tumor specimens of 15 colorectal cancer patients hospitalized in Renmin Hospital of Wuhan University from March 2019 to August 2020 were included. According to the treatment effect, the patients were divided into sensitive group (11 cases) and drug-resistant group (4 cases). The relative expression levels of circ_0008274, downstream SMARCC1and miR-140-3p in colorectal cancer tissues in the two groups were detected by RT-PCR. Independent sample t test was used for statistical analysis. Results:The level of circ_0008274 in DiFi-R cells was 2.33±0.12 times of that of DiFi cells, while the level in Caco-2-R was (2.92±0.42) times of that of Caco-2 cells, and the differences were statistically significant ( t=19.97 and 7.80, both P<0.05). The results of double-luciferase reporter showed that after miR-140-3p mimic combined with wild-type circ_0008274, the relative fluorescence intensity was lower than before (0.28±0.04 vs. 1.00±0.00), and the difference was statistically significant ( t=-30.71, P=0.001). The expression of SMARCC1 protein in DiFi-R and Caco-2-R cells was significantly increased, the expression at protein level was higher than that of DiFi and Caco-2 cells (2.22±0.36 vs. 0.61±0.17, 0.85±0.11 vs. 0.35±0.08), and the differences were statistically significant ( t=6.23 and 6.32, both P<0.01). After circ_0008274 was knocked out, the numbers of colony formation of DiFi-R and Caco-2-R cells were both lower than those of before knockout (36.67±4.04 vs. 66.00±9.54, 17.35±4.04 vs. 52.33±8.02), the relative active cell ratios after interventing by 10, 50, 100, 150 and 200 nmol/L cetuximab were also lower than those of before knockout (DiFi-R cells (73.75±2.75)% vs. (88.10±2.48)%, (56.50±6.66)% vs. (75.15±6.03)%, (35.75±5.32)% vs. (59.63±6.67)%, (24.25±3.30)% vs. (52.40±6.71)%, (6.25±2.75)% vs. (48.60±5.38)%; Caco-2-R cells (63.74±5.25)% vs. (85.76±4.79)%, (56.50±4.20)% vs.(83.50±3.90)%, (46.00±2.94)% vs. (80.00±6.05)%, (35.30±5.56)% vs. (68.30±4.57)%, (12.25±7.37)% vs. (62.40±7.51)%), and the differences were statistically significant ( t=4.90, 6.71, -7.75, -4.16, -5.60, -7.53, -14.02, -6.19, -8.33, -10.10, -9.17 and -9.56, all P<0.01). After transfecting with miR-140-3p mimic, the relative active cell ratios of DiFi-R and Caco-2-R cells interventing by 10, 50, 100, 150 and 200 nmol/L cetuximab were both lower than those transfected with blank control miR (DiFi-R cells (71.55±4.97)% vs. (85.90±2.66)%, (51.58±3.91)% vs. (74.95±6.35)%, (41.23±8.84)% vs. (58.43±7.05)%, (28.60±5.26)% vs. (53.75±5.65)%, (18.90±5.13)% vs. (51.30±3.30)%; Caco-2-R cells (61.75±2.22)% vs. (90.10±1.41)%, (53.25±4.17)% vs. (86.18±2.69)%, (46.38±4.55)% vs. (77.75±6.70)%, (36.10±8.76)% vs. (70.15±4.18)%, (24.25±2.63)% vs. (65.10±7.62)%), and the differences were statistically significant ( t=-5.09, -6.47, -3.05, -6.28, -10.30, -21.48, -12.83, -8.01, -6.79 and -10.12, all P<0.01). After circ_0008274 was knocked out, the SMARCC1 protein level of Caco-2-R cells rescued by pcDNA3.1 SMARCC1 was higher than that of before rescue (0.63±0.19 vs. 0.09±0.03), and the relative active cell ratios after interventing by 10, 50, 100, 150 and 200 nmol/L cetuximab were also higher than that of before rescue ((93.10±3.56)% vs. (83.83±3.97)%, (83.28±4.26)% vs. (60.90±7.02)%, (61.83±2.12)% vs. (50.10±5.59)%, (53.20±3.74)% vs. (40.50±3.42)%, (46.20±4.08)% vs. (30.80±4.82)%), and the differences were statistically significant( t=3.55, 3.52, 5.44, 3.87, 4.64 and 4.88, all P<0.01). The relative expression levels of circ_0008274 and downstream SMARCC1 of colon cancer tissues in the drug-resistant group were higher than those in the sensitive group (6.45±1.32 vs. 2.26±1.39, 12.53±1.60 vs. 3.82±1.56), and the relative expression level of miR-140-3p was lower than that in the sensitive group (3.91±1.25 vs. 7.43±2.23), and the differences were statistically significant ( t=5.22, 9.51, -2.93, all P<0.01). Conclusions:Circular RNA circ_0008274 is highly expressed in colorectal cancer tissues and cetuximab resistant cells, interacts and inhibits miR-140-3p expression, up-regulates SMARCC1, and participates in the occurrence of cetuximab resistance. PcDNA3.1 SMARCC1 rescue can block the sensitization effect of si-circ_0008274 on cetuximab, and can significantly increase cetuximab resistance of colorectal cancer cells.