The identification of nuclear αvβ3 integrin in ovarian cancer: non-paradigmal localization with cancer promoting actions

Abstract

Nuclear translocation of transmembrane proteins was reported in high-grade serous ovarian cancer (HGSOC), a highly aggressive gynecological malignancy. Although the membrane receptor αvβ3 integrin is amply expressed in HGSOC and involved in disease progression, its nuclear localization was never demonstrated. Nuclear αvβ3 was explored in HGSOC cells (OVCAR3, KURAMOCHI, and JHOS4), nuclear localization signal (NLS) modified β3 OVCAR3, Chinese hamster ovaries (CHO-K1) and human embryonic kidney (HEK293) before/after transfections with β3/β1 integrins. We used the ImageStream technology, Western blots (WB), co immunoprecipitations (Co-IP), confocal immunofluorescence (IF) microscopy, flow cytometry for cell counts and cell cycle, wound healing assays and proteomics analyses. Fresh/archived tumor tissues were collected from nine HGSOC patients and normal ovarian and fallopian tube (FT) tissues from eight nononcological patients and assessed for nuclear αvβ3 by WB, confocal IF microscopy and immunohistochemistry (IHC). We identified nuclear αvβ3 in HGSOC cells and tissues, but not in normal ovaries and FTs. The nuclear integrin was Tyr 759 phosphorylated and functionally active. Nuclear αvβ3 enriched OVCAR3 cells demonstrated induced proliferation and oncogenic signaling, intact colony formation ability and inhibited migration. Proteomics analyses revealed a network of nuclear αvβ3-bound proteins, many of which with key cancer-relevant activities. Identification of atypical nuclear localization of the αvβ3 integrin in HGSOC challenges the prevalent conception that the setting in which this receptor exerts its pleiotropic actions is exclusively at the cell membrane. This discovery proposes αvβ3 moonlighting functions and may improve our understanding of the molecular basis of ovarian cancer pathogenesis.

Nuclear αvβ3 integrin expression, post translational modifications and regulation in hematological malignancies

“…Although membrane integrins were shown before to govern nuclear alterations during cancer progression, 36 there is limited information on nuclear integrins and the prevalent conception is that the settings by which integrins initiate their actions is exclusively at the cell membrane. This dogma was challenged by our recent identification of atypical nuclear αvβ3 localization in ovarian cancer models 12 . In this current work we have confirmed this phenomenon in several hematological malignancies in which membrane αvβ3 expression and involvement were reported 9‐11,37‐39 and provided indication for both existence and modifications of the nuclear αvβ3 (Figure 5).…”

“…The identified interactions with the nuclear integrin in T‐ALL and CLL cells, but not in normal immortalized B cells, suggest potential cancer‐relevant roles. Support for this assumption is provided by our recent demonstration of induced tumor growth and oncogenic signaling in ovarian cancer cells ectopically enriched with the nuclear αvβ3 12 …”

“…Its expression was demonstrated in CLL cells, 9 malignant T‐cells 10 and MCL cells 11 . We have recently identified in ovarian cancer models the existence of a nuclear αvβ3 pool, with tumor promoting activities 12 . Such atypical translocation of transmembrane proteins from the cell membrane to the nucleus was reported before for other cancer‐associated receptors, 13,14 but not for integrins.…”

“…We recently identified in ovarian cancer atypical nuclear localization of the αvβ3 integrin with tumor promoting actions. 12 We set to determine whether this localization is not limited to solid tumors and may exist also in hematological malignancies. We studied models of T-ALL (Jurkat cells) and MCL (HMC-1 cells), two rare and aggressive types of leukemia, as well as CLL, the most common chronic adult leukemia.…”

Application of the Interaction between Tissue Immunohistochemistry Staining and Clinicopathological Factors for Evaluating the Risk of Oral Cancer Progression by Hierarchical Clustering Analysis: A Case-Control Study in a Taiwanese Population

“…Besides, our study raised an interesting issue of localization of IHC staining. In previous studies of ovarian cancer, different localizations of thyroid hormone receptors and αvβ3 integrin demonstrated different nuclear and non-nuclear signaling pathway for cancerogenesis [40,41]. The translocation of transmembrane proteins from the cell membrane to the nucleus may be another crucial mechanism [42].…”