Comparative study on cancer cell apoptosis between gastric and intestinal-type human gastric carcinoma

Apoptosis of cancer cells between the gastric and intestinal-type human gastric carcinoma were compared in terms of the expression of oncogene MDM2 and CD68, the histological types, the infiltration depth, and lymph node metastasis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) assay was employed to stain apoptotic cells. Histochemical method(AB-PAS) was applied to stain mucus that is neutral or acidic in nature. Immunohistochemical method (SABC) was used to detect expression of MDM2 and CD6. The results showed that the mean apoptosis index (AI) of total 48 cases was 8.60+/-2.60. AI in the 30 intestinal type cases was significantly higher than that in the 18 gastric type cases (t=4.67, P<0.01). In the 30 intestinal type cases, the spontaneous apoptosis index of MDM2 negative cases was significantly higher than that of the positive cases (t=7.16, P<0.01). And in the 18 gastric type cases, the same result was found. (t=11.39, P<0.01). The MDM2 positive ratio in gastric type cases was higher than that in intestinal type cases (chi2=4.68, P<0.05). There is no significant difference in AI between cases of lymph node metastasis and non-metastasis cases in intestinal type cases (t=0.26, P>0.05). But in the gastric type cases, a significant difference existed (t=5.87, P<0.01). A significant difference in lymph node metastasis ratio was found between the two gastric carcinoma types (chi2=4.48, P<0.05). The CD68 expression ratio in the 30 intestinal type cases was much lower than that in the 18 gastric type cases (t=4.29, P<0.01). AI of 25 MDM2-positive cases was much lower than that of the 23 MDM2-negative cases (t=7.80, P<0.01). CD68 positive ratio in the 25 MDM2-negative cases was much lower than that in the 23 negative cases. The difference was statistically significant (t=10.90, P<0.01). Except for few cells scattering within the cancer nest, most CD68 positive cells infiltrated in the interstitium around the cancer tissue. In the high-AI cases, CD68-positive cells increased. And the CD68-positive cells decreased in low-AI cases (r=0.96, P<0.01). Logistic regression analysis suggested that among the control variables, only AI was a statistically significant factor in the regression model (chi2=9.64, P<0.01). We concluded that (1) the spontaneous apoptosis index in gastric-type cases of gastric carcinoma was significantly lower than that in intestinal type cases; (2) AI in the two types was influenced by the expression of MDM2 and lymph node metastasis, but no visible connection was found between AI and the infiltration depth or histological types; (3) in the intestinal type cases, AI and the CD68-positive cells increased in MDM2-negative cases.