The human breast carcinoma cell line HBL-100 acquires exogenous cholesterol from high-density lipoprotein via CLA-1 (CD-36 and LIMPII analogous 1)-mediated selective cholesteryl ester uptake

Abstract

Aberrant cell proliferation is one of the hallmarks of carcinogenesis, and cholesterol is thought to play an important role during cell proliferation and cancer progression. In the present study we examined the pathways that could contribute to enhanced proliferation rates of HBL-100 cells in the presence of apolipoprotein E-depleted high-density lipoprotein subclass 3 (HDL3). When HBL-100 cells were cultivated in the presence of HDL3 (up to 200 μg/ml HDL3 protein), the growth rates and cellular cholesterol content were directly related to the concentrations of HDL3 in the culture medium. In principle, two pathways can contribute to cholesterol/cholesteryl ester (CE) uptake from HDL3, (i) holoparticle- and (ii) scavenger-receptor BI (SR-BI)-mediated selective uptake of HDL3-associated CEs. Northern- and Western-blot analyses revealed the expression of CLA-1 (CD-36 and LIMPII analogous 1), the human homologue of the rodent HDL receptor SR-BI. In line with CLA-1 expression, selective uptake of HDL3-CEs exceeded HDL3-holoparticle uptake between 12- and 58-fold. Competition experiments demonstrated that CLA-1 ligands (oxidized HDL, oxidized and acetylated low-density lipoprotein and phosphatidylserine) inhibited selective HDL3-CE uptake. In line with the ligand-binding specificity of CLA-1, phosphatidylcholine did not compete for selective HDL3-CE uptake. Selective uptake was regulated by the availability of exogenous cholesterol and PMA, but not by adrenocorticotropic hormone. HPLC analysis revealed that a substantial part of HDL3-CE, which was taken up selectively, was subjected to intracellular hydrolysis. A potential candidate facilitating extralysosomal hydrolysis of HDL3-CE is hormone-sensitive lipase, an enzyme which was identified in HBL-100 cells by Western blots. Our findings demonstrate that HBL-100 cells are able to acquire HDL-CEs via selective uptake. Subsequent partial hydrolysis by hormone-sensitive lipase could provide ‘free’ cholesterol that is available for the synthesis of cellular membranes during proliferation of cancer cells.

DDX5/p68 associated lncRNA LOC284454 is differentially expressed in human cancers and modulates gene expression

“…Towards this objective, we took the approach of both silencing as well as ectopic overexpression of this RNA in HEK293T cells. Silencing of this RNA resulted in perturbation of only a subset of genes (36 up-regulated and 59 down-regulated) among which many genes are also shown to be perturbed in breast cancer [50][51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69]. The association of these genes in the breast cancer was further validated by RT-qPCR analysis in both breast cancer cell lines as well breast cancer tissue samples.…”

Relationships between caveolae and eNOS: everything in proximity and the proximity of everything

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HDL and LDL: Potential New Players in Breast Cancer Development

“…The scavenger receptor class B type I (SR-BI) acts as an HDL receptor and mediates its cholesterol uptake in breast cancer cells [87]. The receptor SR-BI is abundantly expressed in human breast cancer tissue compared with adjacent normal tissue [88].…”