Relationship between DNA ploidy, expression of ki-67 antigen and gastric cancer metastasis

Abstract

AIM To evaluate the relationship between the expression of Ki-67 antigen and the pathobiologi-cal behaviours of gastric cancers especially their distant metastases.

METHODS Fifty-six specimens of gastric cancer routinely fixed in formalin and embedded in paraffin (FFEP) were studied by immunohisto-chemical method.

RESULTS Expression of Ki-67 antigen was sig-nificantly related to the distant metastases to liver, ovary and adrenal gland (P < 0.01), but not related to the histological type, growth pattern, depth of invasion, histological differentiation and the metastases to local lymph nodes (P > 0.05). Furthermore, the Ki-67 antigen expression was significantly related to the DNA aneu-ploidy pattern, which is closely related to poor prognosis (P < 0.05).

CONCLUSION Overexpression of Ki-67 can be used as an objective marker of the proliferative activity for predicting prognosis of gastric can-cer and metastatic potential to distant organs.

Key Words: Ki-67 antigen; neoplasms metastasis; immunoc hemistry; DNA ploidy; stom-ach neoplasms/pathology

INTRODUCTION

Ki-67 is a mouse monoclonal antibody which recog-nizes a nuclear antigen expressed in all phases of the cell cycle except Go and early G1[1]. And Ki-67 im-munoreactivity can thus be used as biomarker for cell proliferation. Anothermethod to measure cell proliferation is flow cytometry. In our study, we detected 56 gastric cancer tissue specimens immuno-histochemically by PcAb-Ki-67 (Dako, A047) and compared with DNA ploidy pattern in order to evaluate the relationship between the proliferative activity of gastric cancer cell and pathobiological behavior of gastric cancer, especially the relationship with the distant organ metastases.

MATERIALS AND METHODS

Materials

Fifty-six specimens of gastric cancer were collected from Cancer Institute of China Medical University. Among these 56 cases, no metastasis was found in 7 cases, 12 were accompanied with liver, 4 with ovar-ian, 1 with adrenal and 47 with lymph node metas-tasis. Tissue blocks from primary and metastatic tu-mours were chosen from each case.

Methods

PcAB to human Ki-67 antigen (A047) was used in this study to identify the proliferative activity of gastic cancer cell. The dilution for Ki-67 was 1:100. Sections were immunostained using the avidin-bi-otin-peroxidase complex method and pressure cook-ing was used to unmask Ki-67 antigen[2].

Evaluation of immunostaining

Four semi-quanti quantitative classes were used for grading: negative(-), no positive cells; weak positive (+), positive cells < 10%; moder ately posi-tive (+ +), the positive cells between 10%-50%; strong positive (+ + +), the positive cells >50%.

DNA ploidy was measured by flow cytometry, the detailed procedures and the stand ard of evalua-tion followed the method reported previously[3].

RESULTS

Expression of the Ki-67 antigen was not related to WHO’s classification and Lauren’s classification (P < 0.05). It was not related to the depth of local in-vasion of gastric cancer (P > 0.05), growth pattern (P > 0.05) and local lymph nodes metastasis (P > 0.05). But the expression of Ki-67 was significantly related to the distant organ metastases (P < 0.005, Table 1) and also related to DNA aneuploidy pat-tern(Table 2).

Table 1 Relationship between expression of Ki-67 antigen and metast asis of gastric cancer.

Metastasis (Mets)	n	Expression of Ki-67 antigen
		+——+ +(%)	+ + +(%)
Non-Mets	7	3(42.9)	4(57.1)
LN Mets	32	23(71.9)	9(28.1)
Distant organ Mets	17	3(17.6)	14(82.4)b
Total	56	29(51.8)	27(48.2)

^bP < 0.01, vs LN (lymph node).

Table 2 Relationship between expression of Ki-67 antigen and DNA ploidy.

DNA ploidy	n	Expression of Ki-67 antigen
		+——+ +(%)	+ + +(%)
Di(Tetra)ploid	35	22(62.9)	13(37.1)
Aneuploid	21	7(33.3)	14(66.7)a

^aP < 0.05.

DISCUSSION

Proliferative activity of cancer cells was closely re-lated to the biological behavior of carcinoma, espe-cially the invasion, metastasis and prognosis. In this study, the results showed that Ki-67 could be used as a marker to measure the proliferative activity of gastric cancer cells and predict the potential of metastasis to distant organs of gastric cancer. The method was simple and quick. The detection of Ki-67 antigen could be used as a useful marker to fore-tell the high risk of the metastases to distant organs and predict the prognosis of gastric cancer.

DNA aneuploidy was one of the markers of malignant tumour cells. Xin, et al[4] had reported that aneuploidy DNA pattern may be related to the development of distant organ metastases, especially through the blood vascular system. The results of this study showed that DNA aneuploidy was related to the expression of Ki-67, the latter was also close-ly related to the distant met astases (P < 0.01). These suggested that the expression of Ki-67 and a-neuploidy DNA pattern are two objective markers which may be valuable in predicting high potential of metastases to the distant organs, and the com-bined detecti on of these two markers could be a more useful method for predicting metastases to the distant organs and prognosis.