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Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance.

ABSTRACT: Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolipids have been well documented. Sphingolipids are known to play many structural and signalling roles in cells, as they are involved in the control of growth, survival, adhesion, and motility. In particular, in order to increase survival, cancer cells: (a) counteract the accumulation of ceramide that is endowed with pro-apoptotic potential and is induced by many drugs; (b) increase the synthesis of sphingosine-1-phosphate and glucosylceramide that are pro-survivals signals; (c) modify the synthesis and the metabolism of complex glycosphingolipids, particularly increasing the levels of modified species of gangliosides such as 9-O acetylated GD3 (?Neu5Ac(2-8)?Neu5Ac(2-3)?Gal(1-4)?Glc(1-1)Cer) or N-glycolyl GM3 (?Neu5Ac (2-3)?Gal(1-4)?Glc(1-1)Cer) and de-N-acetyl GM3 (NeuNH(2)?Gal(1-4)?Glc(1-1)Cer) endowed with anti-apoptotic roles and of globoside Gb3 related to a higher expression of the multidrug resistance gene MDR1. In light of this evidence, the employment of chemical or genetic approaches specifically targeting sphingolipid dysregulations appears a promising tool for the improvement of current chemotherapy efficacy.

SUBMITTER: Giussani P

PROVIDER: S-EPMC3975402 | biostudies-literature | 2014

REPOSITORIES: biostudies-literature

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Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance.

Giussani Paola P Tringali Cristina C Riboni Laura L Viani Paola P Venerando Bruno B

International journal of molecular sciences 20140312 3

Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolip ...[more]

PMID: 24625663

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Project description:BACKGROUND:Invasive lobular breast carcinoma (ILC) is a histological subtype of breast cancer that is characterized by loss of E-cadherin and high expression of estrogen receptor alpha (ER?). In many cases, ILC is effectively treated with adjuvant aromatase inhibitors (AIs); however, acquired AI resistance remains a significant problem. METHODS:To identify underlying mechanisms of acquired anti-estrogen resistance in ILC, we recently developed six long-term estrogen-deprived (LTED) variant cell lines from the human ILC cell lines SUM44PE (SUM44; two lines) and MDA-MB-134VI (MM134; four lines). To better understand mechanisms of AI resistance in these models, we performed transcriptional profiling analysis by RNA-sequencing followed by candidate gene expression and functional studies. RESULTS:MM134 LTED cells expressed ER at a decreased level and lost growth response to estradiol, while SUM44 LTED cells retained partial ER activity. Our transcriptional profiling analysis identified shared activation of lipid metabolism across all six independent models. However, the underlying basis of this signature was distinct between models. Oxysterols were able to promote the proliferation of SUM44 LTED cells but not MM134 LTED cells. In contrast, MM134 LTED cells displayed a high expression of the sterol regulatory element-binding protein 1 (SREBP1), a regulator of fatty acid and cholesterol synthesis, and were hypersensitive to genetic or pharmacological inhibition of SREBPs. Several SREBP1 downstream targets involved in fatty acid synthesis, including FASN, were induced, and MM134 LTED cells were more sensitive to etomoxir, an inhibitor of the rate-limiting enzyme in beta-oxidation, than their respective parental control cells. Finally, in silico expression analysis in clinical specimens from a neo-adjuvant endocrine trial showed a significant association between the increase of SREBP1 expression and lack of clinical response, providing further support for a role of SREBP1 in the acquisition of endocrine resistance in breast cancer. CONCLUSIONS:Our characterization of a unique series of AI-resistant ILC models identifies the activation of key regulators of fatty acid and cholesterol metabolism, implicating lipid-metabolic processes driving estrogen-independent growth of ILC cells. Targeting these changes may prove a strategy for prevention and treatment of endocrine resistance for patients with ILC.

Dataset Information

Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance.

Publications

Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance.

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