金属硫蛋白过表达对乳腺癌化疗方案选择的影响

　　作者：董建峰,马洁华,张,辉,张晓丽,薄爱华　　作者单位：河北北方学院基础医学院解剖教研室,河北 张家口 075000

　　【摘要】目的：探讨金属硫蛋白(Metallothionein，MT)在乳腺癌中过表达的意义及其与乳腺癌化疗方案选择的相关性。方法：利用SP免疫组织化学技术，检测88例乳腺癌组织中MT表达率。结果：MT在乳腺癌中总阳性率为67.05%(59/88)。MT在髓样癌、小叶癌和导管癌中的阳性率分别为41.67%，85.71%和62.50%。在浸润型乳腺癌组阳性率明显高于非浸润型癌组(P<0.05);在小叶癌组阳性率高于髓样癌组和导管癌组(P<0.05);淋巴结转移组阳性率高于非转移组(P<0.05)。结论：MT表达与乳腺癌的病理类型及有否淋巴结转移相关，检测MT对乳腺癌化疗方案的制定有指导意义。

　　【关键词】 金属硫蛋白,乳腺肿瘤,免疫组织化学

　　Since the first report of metallothionein(MT)overexpression in thyroid cancer tissues by Cherian and Nartey in 1987[1],there has been an extensive interest in the role which is played by MT in tumorigenesis.The abnormal increase of MT is related to the genesis,development and drugresistance of tumor[2].To investigate the expression of MT in breast cancer and its clinical significance,we collected 88 cases with breast cancer to examine the expression of MT with streptavidin peroxidase(SP)immunohistochemical method,The aim was to clarify the relation between the expression of MT and the biology characteristic of tumor cell,and offer a base of establishing chemistry treatment scheme.

　　1 Materials and methods

　　1.1 Patients and samples

　　88 cases with breast cancer in women were collected from January 2005 to October 2008 at No.1 Affiliated Hospital Hebei North University in Zhangjiakou.The age range was 30 to 79 years old,the average age was 51.5 years,and the median age was 48.5 years.

　　1.2 Immunohistochemical staining

　　Mouse antimetallothionein antibody was conducted by Santa Cruz,USA.Immunohistochemical staining SP kit and DAB kit were purchased from Beijing Zhongshan Goldenbridge biotechnology Co.Ltd.(China).The samples of cancer were fixed in 100mL/L dehydrated formaldehyde and embedded in paraffin,sections of 5μm thickness were sliced,which were dyed by HE staining method,and all samples were confirmed by pathological diagnosis and clinical classitication.Immunohistochemical SP staining method was used in the experiment with conventional staining procedures.The negative control was designed as PBS instead of antibody I,the positive control was known as positive tissue sections which was provided by Beijing Zhongshan Co.Ltd.(China).

　　1.3 Statistical analysis

　　χ2 test was used for statistical analysis,P value less than 0.05 was considered as statistical significance.

　　2 Results

　　The MT immunoreactive productions was showed brown with yellow color and distributed in cytoplasm of the cancer cells.But the cell nucleus and negative control cell were showed no color(Fig1—3).The relationship between the expression of MT and the biology characteristic of carcinomer cell was showed in Tables 1.

　　Table 1 Relationship between MT expression and pathology type,lymph metastases in breast cancer

　　GroupnBreast Cancer MT(+)n%Total positive rate885967.05Marrow cancer12541.67Lobular cancer282485.71▲Ductal carcinoma483062.50Infiltrating cancer 685276.47△Noninfiltrating cancer20735.00Lymph metastases393076.92★Nonlymph metastases492959.18

　　▲:Positive rate was significantly higher than that of marrow cancer group and ductal carcinoma group(P<0.05);△:Positive rate was significantly higher than that of noninfiltrating cancer group(P<0.05);★:Positive rate was significantly higher than that of Nonlymph metastases group(P<0.05)

　　Fig 1 Infiltrating ductal carcinoma (SP,×400)Fig 2 Infiltrating lobular cancer (SP,×400)Fig 3 Marrow cancer (SP,×400)

　　Discussion

　　The MT is protein of small molecular with much sulfydryl.MT gene is located at chromosome 16.MT proteins are small molecular weight proteins containing 61 to 68 amino acid residue,and are characterized by high cysteine content with a paucity of aromatic acids,there is 25%～30% cysteine of in MT.In human,there are four subgroup of MT proteins,namely MT1,MT2,MT3 and MT4,and each subgroup can be classified into αand β[3].Because MT exhibit the selective chelating power for heavy metal ion such as zine(Zn),copper(Cu),cadmium(Cd)and platinum(Pt),they are involved in heavy metal complex.MT has close relation to absorption，transportation and metabolism of many trace elements.MT has also been implicated in chemoresistance to anticancer drugs and in scavenging free radical in cells[4].The clearance ability of MT is 38.5 times higher than that of glutathione according to the relevant report,especially ZnMT[5].Moreover,MT also participates in the regulation of stress reaction and cell apoptosis.Some reports indicated that the high expression of MT had some relation to the occurrence,development and differentiation of tumor[6].

　　MT gene is inducible,its involvement in tumor drugresistance has attracted much attention[7],Huang Gengwen et al[8]transfected C127 cells of mouse with human MT gene,resulting in 10 times more MT content along with 4.4 times increase of drugresistance to carboplatin, chlorambucil and melpalan.Examined MT of many tumor cell lines,it was found that high expression of MT in cells was accompanied by drugresistance to cisplatin and alkylating agent,while cells with low expression of MT was sensitive to the above anticancer drugs[9].CdCl2 induced inhibition of MT gene expression in mouse embryonic fibrocytes could increase the sensitivity to anticancer drugs.The tumors with high MT expression have drugresistance to electrophilic chemotherapy drugs,it can cut off the effect of the chemotherapy drugs to targeted DNA.When MT meets alkylating agent,it can change on property and structure,then affect the distribution of metal ion in cells,and start multiple chemical reactions,so that the cytotoxicity effect of alkylating agent is reduced.Some experiments demonstrated that tumors with high MT content were resistant to alkylating agents(carboplatin,cisplatin and nitrosocarbamidealkylating agent)and cyclophosphamide,but responsive to fluorouracil(5Fu)and vincristine.The mechanism needs further investigation.[10,11].

　　This study showed that positive rate of MT was higher in breast carcinoma,the total expression rate of MT was 67.05%,and the positive rate of MT in lobular cancer was higher than that of ductal cancer and marrow cancer(P<0.05).The positive rat of MT was significantly higher in infiltrating type of cancer group than that in noninfiltrating type of cancer.The overexpression of MT showed was associated with biology characteristic of breast carcinoma.It was reported that the medicine of platinum(oxaliplatin,cisplatin etc.)is used widely in treating cancer at present,if the patients MT expression is high,his sensitivity will descend with this medicine,but to the patient with MT negative,his sensitivity will increase[12,13].Our experiment indicated that it will enhance chemotherapy effect if drugresistance gene protein examination could be used broadly,it will enhance the rate of existence and the quantity of the patientslife.

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