N-acetyl cysteine inhibits human signet ring cell gastric cancer cell line (SJ-89) cell growth by inducing apoptosis and DNA synthesis arrest.
OBJECTIVE
In this study, we investigated the inhibitory effects of N-acetyl cysteine (NAC) on the growth of the human signet ring cell from the gastric-cancer cell line SJ-89 , via the induction of apoptosis and the arrest of DNA synthesis.


METHODS
SJ-89 cells were regularly incubated in the presence of NAC at 5, 10 and 20 mmol/l, and with IMDM as untreated control. Trypan blue-dye exclusion analysis and 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay were applied to detect cell proliferation. Apoptotic morphology was observed by electron microscopy. Flow cytometry and terminal deoxynucleotidyl transferase-mediated dUTP nick-end-labeling (TUNEL) assay were performed to detect NAC-triggered apoptosis.


RESULTS
NAC could inhibit proliferation of human gastric cancer SJ-89 cells in a dose-dependent and time-dependent manner. The growth curve showed suppression by 15.8, 37.6 and 66.3% following 72 h of NAC treatment at 5, 10 and 20 mmol/l, respectively, similar to the findings of 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide assay. DNA synthesis was evidently reduced by 25, 39 and 91% after 24 h NAC treated at 20 mmol/l and 5 days at 10 and 20 mmol/l, respectively. Cell growth was inhibited by 100% with the treatment of 20 mmol/l NAC on day 6. NAC-treated SJ-89 cells were characterized by typical apoptotic alterations, including morphological changes by electron microscopy, typical apoptotic sub-G1 peaking observed by flow cytometry and increase of apoptotic cells with the elevation of the concentration of NAC in a clearly dose-dependent manner by TUNEL assay. Electrophoresis analysis showed typical 'DNA ladder'.


CONCLUSIONS
The data above implicated that NAC inhibits human gastric-cancer SJ-89 cell growth by inducing apoptosis and DNA synthesis arrest. Although the exact mechanisms involved in NAC-induced apoptosis have not been known up to now, the ability to induce apoptosis in a tumor-cell population within 48 h is worth noting. It is also noteworthy that NAC can selectively inhibit the growth of tumor cells. Further studies are needed to elucidate the mechanisms.
Li
Jian
J
Jiangxi Province Key Laboratory of Molecular Medicine and Institute of Hematology, the Second Affiliated Hospital of Nanchang University, Nanchang, PR China. jenifer_jian@yahoo.com.cn
Tu
Huai-Jun
HJ
Li
Jie
J
Dai
Ge
G
Dai
Yu-Cheng
YC
Wu
Qiong
Q
Shi
Qing-Zhi
QZ
Cao
Qing
Q
Li
Zhen-Jiang
ZJ
D000111:Acetylcysteine / Q000494:pharmacology*; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D018279:Carcinoma, Signet Ring Cell / Q000473:pathology*; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004261:DNA Replication / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000032:analysis / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004353:Drug Evaluation, Preclinical; D006801:Humans; D020287:In Situ Nick-End Labeling; D013274:Stomach Neoplasms / Q000235:genetics / Q000473:pathology*; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D004273:DNA, Neoplasm; D000111:Acetylcysteine