CD98hc (SLC3A2) drives integrin-dependent renal cancer cell behavior

Abstract

BackgroundOverexpression of CD98hc (SLC3A2) occurs in a variety of cancers and is suspected to contribute to tumor growth. CD98, a heterodimeric transmembrane protein, physically associates with certain integrin β subunit cytoplasmic domains via its heavy chain, CD98hc. CD98hc regulates adhesion-induced intracellular signal transduction via integrins, thereby, affecting cell proliferation and clonal expansion. Disruption of CD98hc led to embryonic lethality in mice (E 3.5 and E 9.5) and CD98hc −/− embryonic stem cell transplantation failed to form teratomas, while CD98hc over-expression in somatic cells resulted in anchorage-independent growth. However, it is unclear whether interference with CD98hc expression tumor cell behavior.MethodsRenal cell cancer cell lines have been used to determine the effect of CD98hc expression on cancer cell behavior using cell adhesion, cell trans-migration and cell spreading assays. Flow cytometric analysis was performed to study the rate of apoptosis after detachment or serum starvation. shRNA-lentiviral constructs were used to stably knockdown or reconstitute full length or mutated CD98hc. The role of CD98 as a promotor of tumorigenesis was evaluated using an in in vivo tumor transplantation animal model. Immunohistochemical analysis was performed to analyze cell proliferation and CD98 expression in tumors.ResultsThis report shows that CD98hc silencing in clear cell renal cancer cells reverts certain characteristics of tumorigenesis, including cell spreading, migration, proliferation and survival in vitro, and tumor growth in vivo. Acquisition of tumorigenic characteristics in clear cell renal cancer cells occurred through the integrin binding domain of CD98hc. A CD98hc/integrin interaction was required for adhesion-induced sustained FAK phosphorylation and activation of the major downstream signaling pathways PI3k/Akt and MEK/ERK, while overexpression of a constitutive active form of FAK rescued the CD98hc deficiency.ConclusionsIn this study we demonstrate that loss of CD98hc blocks tumorigenic potential in renal cell cancer.

CD99 inhibits CD98-mediated β1 integrin signaling through SHP2-mediated FAK dephosphorylation

“…Particularly, crosslinking of CD98hc increased adhesion of the small cell lung-cancer cell line (SCLC) H345 and that of breast cancer cells to fibronectin and laminin by inducing conformational changes in β1 integrins [14,15]. The physical association of CD98hc with specific integrin β subunits is required for tumorigenesis of renal cancer cells via sustained FAK phosphorylation and activation of the PI3K/Akt and MEK/ERK signaling pathways [16]. Previous studies indicated that CD98hc-induced FAK phosphorylation was dependent on the β1 integrin-mediated signaling pathway [17][18][19].…”

Dominant Suppression of β1 Integrin by Ectopic CD98-ICD Inhibits Hepatocellular Carcinoma Progression

“…While regulated activation of integrins is critical for tissue homeostasis, overexpressed β1-integrin detected in several types of human cancers indicated poor prognosis, and it is associated with metastasis and chemo-resistance of cancer cells [12,13,14]. Indeed, integrin-dependent events, such as survival, proliferation, migration and even malignant transformation can be activated by CD98 without integrin ligation or extracellular matrix engagement [10,15,16,17,18]. Recently, CD98 was reported to enable matrix assembly and support RhoA-driven contractility, and it contributed to carcinogenesis by amplifying a positive feedback loop, which increases both extracellular matrix stiffness and resulting cellular responses [15].…”

CD98 Regulates Vascular Smooth Muscle Cell Proliferation in Atherosclerosis

“…Male mice of each genotype, [8][9][10] weeks old, were put on HFD for 16 weeks to allow the establishment of VSMC-rich atherosclerotic plaque.…”

“…The protein has dual functions, including transporting large, neutral amino acids via its interaction with various light chains, and mediating integrin signaling via its cytoplasmic tail, specifically β1-or β3-integrins 1314, 15 . Together, these functions serve to regulate cell survival, proliferation, migration and even malignant transformation 10,16 .…”

“…CD98 is a transmembrane protein made up of a heavy chain (CD98hc) and one of several light chains that is involved in biological events and diseases that require proliferative and migratory processes, including cancer 10 and several autoimmune diseases 11,12 . The protein has dual functions, including transporting large, neutral amino acids via its interaction with various light chains, and mediating integrin signaling via its cytoplasmic tail, specifically β1-or β3-integrins 1314, 15 .…”