[RNPC1 induces sensitivity of HER-2-positive breast cancer BT474 cells to trastuzumab through upregulation of HER2]

OBJECTIVE

To explore the sensitivity of HER-2-positive BT474 breast cancer cells to trastuzumab after knockdown or overexpression of RNA binding protein 38 (RNPC1).

METHODS

The expressions of RNPC1 and HER-2 mRNA were detected by qRT-PCR, and the expressions of RNPC1, HER-2 and PI3K/AKT proteins were detected by Western blot after transfected with RNPC1 lentiviral vector, respectively. The experimental groups were treated with different concentration of trastuzumab, and cell apoptosis rate was analyzed by 7-AAD/APC double staining flow cytometry, and cell growth inhibition rate was tested by cell counting kit 8 (CCK-8). The expression of apoptosis-related proteins was detected by Western blot assay.

RESULTS

The results of qRT-PCR showed that overexpression of RNPC1 increased the expressions of RNPC1 and HER-2 mRNA, and the expressions of RNPC1 and HER-2 were decreased after RNPC1 knockdown. The knockdown of RNPC1 decreased the expressions of RNPC1 and HER-2. Moreover, overexpression of RNPC1 decreased and knockdown of RNPC1 increased the levels of p-PI3K and p-AKT while the total protein expressions of both were marginally changed.The results of analysis using a cell counting CCK-8 kit showed that the RNPC1 overexpressed group had a higher growth inhibition rate [(20.33±1.25)%, (35.38±2.05)%, (50.43±2.12)%, (65.35±2.08)% and(76.00±2.16)%, respectively] than that of the control group [(13.67±1.24)%, (27.86±2.05)%, (39.72±1.69)%, (53.33±1.70)% and(62.68±2.07)% ] when treated with different concentrations of trastuzumab (5, 10, 15, 20 and 25 μg/ml). The cell apoptosis rates in the RNPC1-overexpressed group [(19.46±1.06)%, (30.87±0.98)%, (50.45±1.13)%, respectively] were also increased compared with that in the control group [(14.38±0.64)%, (21.65±1.24)%, (38.03±0.85)%] when treated with different concentrations of trastuzumab (0, 10, 20 and 30 μg/ml)(P<0.05 for all). Reverse results were observed in the RNPC1 knockdown experiments [experimental groups: (9.67±1.18)%, (21.67±1.23)%, (30.33±1.25)%, (40.33±1.69)%, and (53.00±1.63)%] compared with those of control groups: [(14.00±0.82)%, (27.67±1.25)%, (39.67±1.79)%, (53.67±1.50)%, and (63.33±1.52)%]; and experimental groups: [(11.64±0.68)%, (16.60±1.01)%, and (25.14±3.12)%] compared with those of the control groups: [(14.71±0.61)%, (22.65±0.96)%, and (39.03±0.85)%]. The overexpression of RNPC1 increased the expression levels of Bim and Bad and decreased the level of Bcl-xl, and reverse result was observed after knockdown of RNPC1.

CONCLUSION

RNPC1 may promote the sensitivity of breast cancer cells to trastuzumab through the increased expression of HER-2 in the BT474 breast cancer cells.

High casein-lactalbumin diet accelerates blood coagulation in rats

This study investigates the influence of a high protein intake on normal hemostasis, fluid balance and organ growth. Adult rats were fed semipurified diets that contained either 18 or 56 g/100 g casein-lactalbumin for 2 wk, and the following functions were measured: food and water intake, weight gain, blood pressure, bleeding and clotting time, ADP-stimulated platelet aggregation, thrombin time, prothrombin time and partial thromboplastin time. Although food intake was depressed by the high protein diet, weight gain was not affected by the regimen. Water consumption, 24-h urine excretion and kidney weight were significantly greater in rats fed the high protein diet than in controls. High protein intake resulted in shorter barbiturate-induced sleeping time. Bleeding time and clotting time were significantly lower in rats fed the high protein diet for 7 d. However, heart rate, mean arterial pressure, plasma protein and osmolarity, platelet aggregation, prothrombin time, partial thromboplastin time and thrombin time did not differ significantly. Because a high protein intake caused rapid coagulation of blood in rats without affecting the activity of clotting factors, we suggest that this diet sensitized rats to factors that initiate clotting in vivo.