Clinical & Experimental Metastasis 20: 599–609, 2003. © 2003 Kluwer Academic Publishers. Printed in the Netherlands. 599 Expression of the 67 kDa laminin receptor and the α6 integrin subunit in serous ovarian carcinoma Vered Givant-Horwitz 1 , Ben Davidson 2 , Gregg van de Putte 3 , Hiep Phuc Dong 2 , Iris Goldberg 4 , Sivan Amir 1 , Gunnar B. Kristensen 3 & Reuven Reich 1,5 1 Department of Pharmacology and Experimental Therapeutics, Faculty of Medicine, Hebrew University, Jerusalem, Israel; 2 Department of Pathology, The Norwegian Radium Hospital, Montebello, Oslo, University of Oslo, Norway; 3 Department of Gynecologic Oncology, The Norwegian Radium Hospital, University of Oslo, Montebello, Oslo, Norway; 4 Department of Pathology, Sheba Medical Center, Tel-Hashomer, Israel, affiliated with Sackler School of Medicine, Tel-Aviv University, Israel; 5 Affiliated with the David R. Bloom Center for Pharmacy at the Hebrew University Received 6 January 2003; accepted in revised form 24 April 2003 Key words: integrins, laminin receptors, metastasis, mRNA in situ hybridization, prognosis Abstract The aim of this study was to analyze the expression of two laminin receptors, the 67kDa laminin receptor (LBP) pre- cursor and the α6 integrin subunit, in effusions and solid tumors of patients diagnosed with serous ovarian carcinoma and to evaluate their predictive role. Eighty-eight effusions and one hundred sixteen primary (= forty-one) and metastatic (= seventy-five) ovarian carcinomas were evaluated for expression of the above-mentioned mRNAs using in situ hybridiz- ation (ISH). LBP protein expression was studied in 24 effusions and 43 solid tumors using immunohistochemistry (IHC). α6 integrin subunit protein expression was studied in 27 effusions using flow cytometry (FCM). Expression of LBP mRNA was frequently detected in both carcinoma (92 of 116 cases, 79%) and stromal (79 of 116 cases, 68%) cells in solid tumors. Expression was still higher in cancer cells in effusions (85 of 88 specimens, 96%). In contrast, α6 integrin subunit was less frequently detected in both solid tumors (33 of 116; 28% in carcinoma cells, 23 of 116; 20% in stromal cells) and effusions (36 of 88; 41%). LBP protein expression was found in 19 of 24 (79%) effusions and 40 of 43 (93%) solid tumors, and was higher in effusions of patients who received chemotherapy prior to tapping (P = 0.024). FCM showed protein expression of the α6 integrin subunit in 17 of 27 (63%) effusions. Expression of the α6 integrin subunit mRNA in tumor cells of solid lesions was significantly lower in solid tumors of FIGO stage-IV patients compared to those of patients diagnosed with stage-III-disease (P = 0.004), and its absence predicted significantly shorter overall survival (OS) in univariate analysis (P = 0.018). Absence of α6 integrin subunit protein expression using FCM predicted median OS of 12 months compared to 26 months for patients with tumors expressing the protein, although this finding did not reach significance (P = 0.27). In conclusion, as opposed to previous reports, both mRNA and protein expression of the α6 integrin subunit do not appear to be down-regulated in effusions compared to solid tumors. Loss of α6 integrin subunit mRNA (and possibly protein) expression is a novel prognostic marker in advanced-stage ovarian carcinoma. LBP mRNA and protein expression is independent of that of the α6 integrin subunit in both solid tumors and effusions of serous ovarian carcinoma. Abbreviations: DMSO – dimethoxy sulfoxide; FCM – flow cytometry; FITC – fluorescein isothiocynate; IHC – Immunohistochemistry; ISH – in situ hybridization; LBP – laminin-binding protein; NBT-BICP – nitroblue tetrazolium- 5-bromo-4-chloro-3-indolyl phosphate; PE – phycoerythrin; PerCP – peridinin chlorophyll protein Introduction Local invasion and distant metastasis are the main factors responsible for cancer-related morbidity and mortality. Breaching and degradation of the basement membrane (BM) is a key event in these processes and signifies the transition from a contained in situ lesion to an invasive and poten- tially disseminated tumor in epithelial malignancies. The Correspondence to: Dr Ben Davidson, Department of Pathology, The Norwegian Radium Hospital, Montebello N-0310 Oslo, Norway. Tel: +47-22934871; Fax: +47-22508554; E-mail: bend@ulrik.uio.no BM, a thin layer of extracellular matrix that physiologic- ally supports epithelial, endothelial and mesenchymal cells, is composed of several proteins, including laminins, the major non-collagenous protein, type-IV collagen, and pro- teoglycans [1]. Laminin is a large glycoprotein composed of various α, β and γ -chains, forming at least 12 isoforms [1]. Laminin receptors fall into two categories: integrin and non-integrin. Integrins, a family of heterodimeric glycoproteins, are composed of α- and β -subunits [2]. Eighteen α and eight β subunits are known to date, forming twenty-five different