[Study on the correlation between high expression of FHL1 in gastric cancer cells and cisplatin resistance]

To investigate the correlation between Four and a half LIM domains protein 1 (FHL1) and cisplatin resistance in gastric cancer (GC), and to evaluate its prognostic value. The mRNA expression levels of FHL1 were analyzed in pre-treatment (n=22) and acquired-resistance (n=22) gastric cancer tissues using the Gene Expression Omnibus (GEO) database. Immunohistochemistry was employed to validate FHL1 expression in chemo-resistant (n=25) versus chemo-sensitive (n=26) GC tissues and to analyze its correlation with survival prognosis. Western blot and RT-qPCR were used to detect FHL1 protein and mRNA levels in cisplatin-resistant and parental GC cell lines. Stable gastric cancer cell lines with FHL1 knockdown and overexpression were constructed. The Cell Counting Kit-8 (CCK8) assay was used to assess cell viability under cisplatin treatment. The TUNEL assay was employed to detect the rate of apoptosis after cisplatin treatment. Furthermore, an in vivo xenograft mouse model was established to evaluate the impact of FHL1 on tumor growth following cisplatin administration. The results showed that bioinformatic analysis revealed that FHL1 was highly expressed in drug-resistant gastric cancer tissues (P<0.001). Survival analysis indicated that high FHL1 expression was associated with a lower overall survival rate in patients (P<0.001). Among 51 gastric cancer samples, FHL1 expression was significantly higher in the chemotherapy-resistant group compared to the sensitive group (P<0.001). FHL1 was identified as an independent risk factor for gastric cancer (P<0.01), and patients with high FHL1 expression had a shorter overall survival (P<0.05). Western Blot experiments showed that FHL1 expression was upregulated in SGC7901/DDP cells (0.99±0.22 vs. 0.53±0.16, t=2.90, P<0.05) and AGS/DDP cells (1.16±0.23 vs. 0.62±0.21, t=3.60, P<0.05) compared to their respective parental cells. In AGS/DDP cells, FHL1 overexpression increased Bcl-2 expression (1.26±0.16 vs. 0.61±0.16, t=4.94, P<0.01) and decreased Bax expression (0.24±0.02 vs. 0.65±0.20, t=3.55, P<0.05) compared to the control group. Conversely, FHL1 knockdown decreased Bcl-2 expression (0.24±0.06 vs. 0.57±0.06, t=6.82, P<0.01) and increased Bax expression (1.37±0.14 vs. 0.60±0.13, t=6.89, P<0.01). CCK8 assays demonstrated that FHL1 overexpression enhanced the survival rate of AGS/DDP and SGC7901/DDP cells under cisplatin treatment (P<0.001), while FHL1 knockdown showed the opposite effect (P<0.001). TUNEL assays revealed that the proportion of apoptotic cells was significantly reduced in the FHL1 overexpression group (9.0%±2.8%) compared to the control group (26.0%±7.8%) (P<0.05), and significantly increased in the FHL1 knockdown group (79.8%±10.7%) compared to its control (25.7%±5.9%) (P<0.01). In vivo, the FHL1 overexpression group exhibited significantly increased tumor weight (1.39±0.17)g vs. (0.85±0.21) g and volume (1 394.43±204.71)mm³ vs. (830.01±292.95) mm³ (P<0.001), while the FHL1 knockdown group showed significantly reduced tumor weight (0.34±0.06)g vs. (0.89±0.16) g and volume (166.51±46.22)mm³ vs. (790.87±118.63) mm³ compared to their respective control groups (P<0.001). In conclusion, FHL1 promotes cisplatin resistance in gastric cancer by inhibiting apoptosis, leading to a poor prognosis. This suggests that FHL1 could be a potential therapeutic target and a biomarker for monitoring drug resistance.