Research Of The Relationship Between Osteopontin And Clinicopathological Features Of Breast Cancer

Background and ObjectiveOsteopontin(OPN) is a chemokine like phosphorylated glycoprotein that plays important role in cancer progression.The elevated expression of osterpontin has been observed in several cancers,thus,this protein is considered as a potent prognostic marker during tumor progression.Studies have found that OPN levels are elevated in the primary tumors of patients with breast cancer,which has been correlated with poor prognosis and was found to be a metastasis associated protein in breast cancer.The goal of the study was to investigated the relationship between OPN expression and clinicopathologic characteristics through examination of the expression of osteopontin in mRNA and protein level in breast cancer patients,thus providing additional support for OPN functioning and better understand of the progression of the breast cancer.Methods94 patients with primary breast carcinoma underwent modified radical mastectomy, lumpectomy or breast conserving surgery at Ji'nan Central Hospital of Shandong University(Jinan,China) from April 2006 to July 2007.The median age of the patients was 49 years(range,33-72 years).The mRNA level expression of OPN were semi-quantitively detected by reverse transcription polymerase chain reaction (RT-PCR) in 66 breast cancers,37 normal breast tissues adjacent to cancer(＞5cm) and 28 benign breast tumor specimens.OPN protein expression was determined by immunohistochemical staining of tissue section using goat anti-human monoclonal antibody OPN(mab53,Santa Cruz Biotechnology,Santa Cruz,USA) as primary sera. The overall amount of staining for OPN was determined based on staining intensity(I) and proportion/extent(E) of stained tumor cells as described by Tuck et al.The proportion score represented the estimated fraction of positively staining tumor cells (0=none;1=＜1/100;2=1/100-1/10;3=1/10-1/3;4=1/3-2/3;5=＞2/3).The intensity score represented the estimated average staining intensity of positive tumor cells (0=none,1=weak,2=intermediate,3=strong).The overall amount of positive staining was expressed as the sum of the proportion and intensity scores(ranges =0 for negative staining and 2-8 for positive staining).Calcification was evaluated by three imaging experts who worked independently and know nothing about patient's clinical information.Results(1) By RT-PCR methods,the OPNmRNA expression was 0.47±0.150 and 0.33±0.09 in breast cancer tissues and benign breast tumors respectively,which showed a statistic significance(P＜0.01).The OPNmRNA showed a higher level in patients with c-erbB-2 ovexpression or axillary lymph node metastasis,which showed a statistic significance too(P=0.015,P=0.004).But it was negative correlated to histological subtype,tumor grade and TNM stage(P=0.14,P=0.073 and P=0.47, respectively).Age,primary tumor size,and the number of axillary lymph node metastases were not significantly associated with OPNmRNA expression(P＞0.05).The brightness of electrophoretic bands of the 42 cases with microcalcification on mammogram was obvious higher than that in the cases without microcalcification.The ratio of OPN toβ-action of microcalcification group and without microcalcification group was 0.52±0.15,0.40±0.14 respectively,there was a significant deviation(P=0,014).There was no obvious difference between the expression of OPNmRNA and the number of calcifications or the calcification patterns(P＞0.05).(2) Immunohistochemical analysis of OPN expression was performed on the 95 primary tumors.Mean OPN score was significantly higher in invasive breast carcinoma(4.83) than that in normal breast tissues(1.86) or benign tumor tissues(2.18).The differenes of OPN expression between the patients with axillary lymph node metastasis and those without axillary lymph node metastasis showed a statistic significance(P=0.048).Similarly,the OPN expression of primary tumor were significantly associated with those of metastatic axillary lymph node (P=0.03),whereas,histological subtype,tumor grade and TNM stage were not(P=0.50, P =0.41 and P=0.80,respectively).OPN was more common in patients with c-erbB-2 ovexpression than those without c-erbB-2 overexpression,although there was not significant difference between them(P=0.056).The Mean OPN score in calcification group were 5.24,compared with non-calcification group(4.11),there were obviously differential expression(P=0.032).There was no obvious difference between the expression of OPN protein and the number of calcifications or the calcifcation patterns too(P＞0.05).Conclusion(1) In breast cancer patients,OPN highly expressed in mRNA level and protein level,which was significantly associated with axillary lymphy nodes metastases and calcification,whereas,histological subtype,tumor grade and TNM stage were not. Age,primary tumor size,and the number of axillary lymph node metastases were not significantly associated with OPNmRNA and OPN protein expression.(2) OPN may be a tumor marker for breast cancer with good sensitivity and specificity.In breast cancer patients,OPN can reflect the tumor burden.Additional prospective and retrospective studies are warranted to better understand the role of OPN expression,to further refine prognosis,and to optimize treatment in patients with breast cancer.OPN may be a addition for histopathology detection and a new evidence for early diagnose,recur monitoring and combined therapy.