Objective:To investigate the mechanism of endoplasmic reticulum (ER) stress-induced chemoresistance to cisplatin in gastric cancer cells. Methods:ER stress models were established in both BGC823 and SGC7901 gastric cancer cells. The expression of GRP78, an ER stress marker, was examined by Western blot analysis. Moreover, whether ER stress can decrease the sensitivity of gastric cancer cells to cisplatin and activate P38 was explored by flow cytometry and Western blot analysis, respectively. Whether ER stress-induced chemoresistance to cisplatin can be abrogated by blocking P38 activity in gastric cancer was also elucidated using flow cytometry. Results:GRP78 protein expression markedly increased after treating BGC823 and SGC7901 gastric cancer cells with tunica-mycin (TM) or thapsigargin (TG) for 8, 16, and 24 h (P<0.05), compared with that in the group treated for 0 h. The apoptotic rates of TM-(or TG)-, cisplatin-, and TM (or TG) plus cisplatin-treated groups significantly increased (P<0.05) in both BGC823 and SGC7901 gastric cancer cells compared with the rate in the control group. The apoptotic rate of TM (or TG) plus cisplatin-treated group signifi-cantly decreased (P<0.05) in both BGC823 and SGC7901 gastric cancer cells compared with that of the cisplatin-treated group. Com-pared with the group treated for 0 h, phospho-P38 expression markedly increased after treating BGC823 and SGC7901 gastric cancer cells with TM (or TG) for 8, 16, and 24 h (P<0.05). No difference in P38 protein expression was observed between each group in both BGC823 and SGC7901 gastric cancer cells (P>0.05). Both P38 inhibitors, either SB203580 or PD169316, can inhibit the activation of P38. The inhibition of P38 activity can overcome ER stress-induced chemoresistance to cisplatin in gastric cancer cells (P<0.05). Con-clusion:ER stress can trigger the chemoresistance to cisplatin by activating P38 in gastric cancer cells.

AIM: To clone and express mouse canstatin (m canstatin)cDNA and provide a basis for the further research on its anti-angiogenic activity and potential application for cancer therapy. METHODS: Total RNA was extracted from mouse liver tissue by Trizol Reagent, and mouse canstatin cDNA was amplified by RT- PCR, then cloned into vector pMD18-T for sequencing. pET30a(+)-m canstatin recombinant plasmid was constructed and expressed in E.coli BL21 with induction of IPTG. RESULTS: Mouse canstatin cDNA is 684 bp coding 227 amino acids. The sequences of both cDNA and amino acid share high homology with human canstatin, with cDNA identity at 89% and amino acids identity at 96% to human canstatin. In the present study, pET30a(+)-m canstatin recombinant plasmid was expressed in E.coli BL21. CONCLUSION: Mouse canstatin cDNA has been cloned for the first time. Constructed pET30a(+)-m canstatin recombinant plasmid is highly expressed in E.coli BL21.

Chinese hamster ovary (CHO) cells are the preferred host cells for the production of complex recombinant therapeutic proteins. Adenine phosphoribosyltransferase (APRT) is a key enzyme in the purine biosynthesis step that catalyzes the condensation of adenine with phosphoribosylate to form adenosine phosphate AMP. In this study, the gene editing technique was used to knock out the aprt gene in CHO cells. Subsequently, the biological properties of APRT-KO CHO cell lines were investigated. A control vector expressed an enhanced green fluorescent protein (EGFP) and an attenuation vector (containing an aprt-attenuated expression cassette and EGFP) were constructed and transfected into APRT-deficient and wild-type CHO cells, respectively. The stable transfected cell pools were subcultured for 60 generations and the mean fluorescence intensity of EGFP in the recombinant CHO cells was detected by flow cytometry to analyze the EGFP expression stability. PCR amplification and sequencing showed that the aprt gene in CHO cell was successfully knocked out. The obtained APRT-deficient CHO cell line had no significant difference from the wild-type CHO cells in terms of cell morphology, growth, proliferation, and doubling time. The transient expression results indicated that compared with the wild-type CHO cells, the expression of EGFP in the APRT-deficient CHO cells transfected with the control vector and the attenuation vector increased by 42%±6% and 56%±9%, respectively. Especially, the EGFP expression levels in APRT-deficient cells transfected with the attenuation vector were significantly higher than those in wild-type CHO cells (P < 0.05). The findings suggest that the APRT-deficient CHO cell line can significantly improve the long-term expression stability of recombinant proteins. This may provide an effective cell engineering strategy for establishing an efficient and stable CHO cell expression system.
Adenine/metabolism* ; Adenine Nucleotides ; Adenine Phosphoribosyltransferase/genetics* ; Adenosine Monophosphate ; Animals ; CHO Cells ; Cricetinae ; Cricetulus ; Recombinant Proteins/genetics*