LNK (SH2B3) is an adaptor protein studied extensively in normal and malignant hematopoietic cells. In these cells, it downregulates activated tyrosine kinases at the cell surface resulting in an antiproliferative effect. To date, no studies have examined activities of LNK in solid tumors. In this study, we found by in silico analysis and staining tissue arrays that the levels of LNK expression were elevated in high-grade ovarian cancer. To test the functional importance of this observation, LNK was either overexpressed or silenced in several ovarian cancer cell lines. Remarkably, overexpression of LNK rendered the cells resistant to death induced by either serum starvation or nutrient deprivation, and generated larger tumors using a murine xenograft model. In contrast, silencing of LNK decreased ovarian cancer cell growth in vitro and in vivo. Western blot studies indicated that overexpression of LNK upregulated and extended the transduction of the mitogenic signal, whereas silencing of LNK produced the opposite effects. Furthermore, forced expression of LNK reduced cell size, inhibited cell migration and markedly enhanced cell adhesion. Liquid chromatography-mass spectroscopy identified 14-3-3 as one of the LNK-binding partners. Our results suggest that in contrast to the findings in hematologic malignancies, the adaptor protein LNK acts as a positive signal transduction modulator in ovarian cancers.
IHC staining of ovarian cancer tissue array stained with LNK antibody #1, Normal ovary 1; #2, Normal ovary 2; #3, Benign ovarian tumor; #4, Clear cell ovarian carcinoma; #5,Serous Cystadenocarcinoma of the ovary (Grade I); #6, Serous cystadenocarcinoma (Grade II); #7, Serous cystadenocarcinoma (Grade III); #8, Serous cystadenocarcinoma (Grade III); #9, Endometrioid carcinoma of the ovary (Grade I), #10, Endometrioid carcinoma (Grade II) #11, Endometrioid carcinoma (Grade III), #12, Endometrioid carcinoma (Grade III).
L-W Ding1,6, Q-Y Sun1,6, D-C Lin1,2, W Chien1, N Hattori1, X-M Dong3, S Gery2, M Garg1, NB Doan4, JW Said4, J-F Xiao1, H Yang1, L-Z Liu1, X Meng1, RY-J Huang1, K Tang3 and HP Koeffler1,2,5
1Cancer Science Institute of Singapore, National University of Singapore, Singapore, Singapore; 2Division of Hematology/Oncology, Cedar-Sinai Medical Center, UCLA School of Medicine, Los Angeles, CA, USA;
3School of Biology Science, Nanyang Technological University, Singapore, Singapore;
4Santa Monica-University of California, Los Angeles Medical Center, Los Angeles, CA, USA
5National University Cancer Institute, National University Hospital Singapore, Singapore, Singapore. Correspondence: Dr L-W Ding, Cancer
Science Institute of Singapore, National University of Singapore, #13 North, MD6, 14 Medical Drive, Singapore 117599, Singapore.
6These authors contributed equally to this work.