Modulation of insulin/IGFs pathways by sirtuin-7 inhibition in drug-induced chemoreistance

• Published in: Diagnostic pathology 2014-05, Vol.9 (1), p.94-94, Article 94
• Main Authors: Aljada, Ahmad, Saleh, Ayman M, Al Suwaidan, Salem
• Format: Article
• Language: English
• Subjects: Aging; Analysis; Apoptosis; Blotting, Western; Breast cancer; Cancer therapies; Cell Line, Tumor; Colleges & universities; Cytotoxicity; Drug resistance; Drug Resistance, Neoplasm - physiology; Health sciences; Humans; Insulin; Insulin - metabolism; Kinases; Medical equipment and supplies industry; Medical test kit industry; Metabolism; Military reserves; Parenting; Physiological aspects; Real-Time Polymerase Chain Reaction; Reverse Transcriptase Polymerase Chain Reaction; RNA polymerase; Signal Transduction - physiology; Sirtuins - metabolism; Somatomedins - metabolism; Transfection; Tumors
• ISSN: 1746-1596; 1746-1596
• DOI: 10.1186/1746-1596-9-94

Insulin and insulin-like growth factors (IGFs) are key regulators of metabolism and growth. Recent evidences suggest a key role of these pathways in non-classical tissues and the metabolic pathways by which these hormones exert their effects in neoplasia is unclear. To study insulin/IGFs pathways in drug sensitive and resistant cancer cells representing breast cancer (MCF-7), osteosarcoma (SaOS-2), and ovarian cancer (A2780) and to examine the effect of Sirtuin-7 (Sirt7) inhibition on insulin/IGFs pathways in MCF-7 cell line. Drug resistant cells were generated by continuous incubation of parental cell lines with stepwise increases in Doxorubicin or Cisplatin over a period of 3 to 6 months. MCF-7 cells were transfected with cloned hairpin siRNA template for Sirt7 using the Amaxa GmbH transfection system. mRNA expression of Sirt7, INSR, IRS-1, IRS-2, IRS-4, IGF-1, IGF-2, MDR-1, MRP-1, BCRP was measured by qPCR and Sirt7 by standard Western blotting. FITC-insulin uptake was imaged with Leica Confocal Microscope. Insulin receptor (INSR), insulin receptor substrate-1 (IRS-1) were inhibited in drug-induced resistance, whereas IRS-2 was significantly induced in all the chemoresistant cells tested when compared to their parental counterparts. IGF-1 and IGF-2 were also upregulated in all the drug resistant cells tested. Sirt7 was significantly reduced in all chemoresistant cells tested. Knockdown of Sirt7 expression in human breast MCF-7 cell line by siRNA induced premature senescence-like phenotype and multi-drug resistance, suggesting that this gene may play an active role in regulating cancer cell response to stress. Suppression of Sirt7 selectively inhibited INSR and IRS-1, whereas it had minimal effect on that of IRS-2. Sirt7 suppression in MCF-7 also inhibited insulin uptake. Additionally, Sirt7 inhibition upregulated IGF-1, IGF-2 and IGFR expression. Our data demonstrate that stress-induced Sirt7 inhibition significantly increases stress resistance and modulates insulin/IGF-1 signaling pathways. More importantly, this study links Sir2 family proteins to insulin/IGF signaling in drug-induced stress resistance in neoplasia. The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1135426681234493.