HSP90 inhibitor AUY922 abrogates up-regulation of RTKs by mTOR inhibitor AZD8055 and potentiates its antiproliferative activity in human breast cancer
Authors: Yi Su
Ling-Hua Meng
Si-Meng Chen
Yan-Yan Shen
Chen-Liang Guo
Yi-Chao Xu
Jian Ding
Yi Chen
Jia-Jie Shi
Journal: International journal of cancer (2014)
Discipline: CLINICAL MEDICINE
Keywords: HSP90 inhibitor; breast cancer; drug combination; mTOR kinase inhibitor; receptor tyrosine kinases.
Affiliations: Division of Anti-Tumor Pharmacology, State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, Shanghai, 201203, People's Republic of China., Division of Anti-Tumor Pharmacology, State Key Laboratory of Drug Research; Shanghai Institute of Materia Medica, Chinese Academy of Sciences; Shanghai 201203 People's Republic of China

Abstract:  mTOR inhibition led to activation of upstream receptor tyrosine kinases (RTKs) and AKT, which may attenuate the efficacy of mTOR kinase inhibitors. We sought to discover efficient drug combination with mTOR inhibitors by elucidating the survival feedback loops induced by mTOR inhibition in breast cancer. The feedback signaling upon treatment of mTOR inhibitor AZD8055 was determined and the combinatorial activity of AZD8055 and HSP90 inhibitor AUY922 in cell signaling and proliferation were detected. Treatment of breast cancer T47D cells with AZD8055 induced activation of AKT and phosphatidylinositol 3-kinase (PI3K), which was accompanied with increase in expression of multiple upstream proteins including EGFR, HER2, HER3 and IRS-1. Different RTKs were revealed to be responsible for the reactivation of AKT by AZD8055 in different breast cancer cell lines. Down-regulation of these proteins differentially enhanced the antiproliferative activity of AZD8055. AZD8055 and AUY922 displayed synergistic effect against a panel of human breast cancer cells irrespective their genotype, which was associated with enhanced cell cycle arrest and inhibition of DNA synthesis. AUY922 destabilized multiple tested tyrosine kinases and abrogated activation of AKT induced by AZD8055. AZD8055 also inhibited up-regulation of HSP70 and HSP27 upon AUY922 treatment. Cotreatment of these two drugs demonstrated synergistic activity against triple negative MDA-MB-468 xenograft without enhanced toxicity. The combination of AZD8055 and AUY922 demonstrated synergistic activity against various types of breast cancer and established a mechanistic rationale for a combination approach using catalytic mTOR kinase inhibitor and HSP90 inhibitor in the treatment of breast cancer. 

Retracted: No

PubPeer comments:
 What appears to be the same actin control blot has appeared in four publications, in some instance more than once in the same paper. Figure 6b in the current paper (#4 below) is the most recent addition to the list. In three cases it is in blots from mice (liver twice, adipose tissue once) and in one case in a blot of extracts from cultured cells (3T3-L1). The descriptions and figure legends that follow were taken from the papers 1. Obesity (Silver Spring). 2014 March From methods:  In brief, male obese mice (B6v-Lep obese J) were purchased from Harlan (Chicago, IL) at the age of 8 weeks. Legend  Figure 1. A) Western blot and densitometry analyses of liver HO-1 and actin; 2. International Journal of Molecular Sciences 2019, 20, 3205.  Figure 2. E_ect of AngII exposed to 3T3-L1 murine pre-adipocytes by Western blot analysis for protein expression of (A) HO-1, (B) SIRT1, (C) CYP11B2, (D) MR, and (E) IR-_, shown as mean band densities 3. Journal of Nutrition and Metabolism 2017;2017:Article ID 4964571.  Figure 2: Effect of HO-1 induction on gp91phox, GST, and nuclear NRF2 protein levels in liver of lean and obese mice. Western blot and densitometry analysis of (a) gp91phox, (b) GST, (c) nuclear NRF2, (d)HO-1, and (e)HO-2 protein levels.  Male obese (ob) mice (B6v-Lep ob J) were purchased from Harlan (Chicago, IL) at the age of 7 weeks and used at the age of 8 weeks. Age- and sex-matched lean mice (B6.V, lean; Harlan) were used as controls. 4 International Journal of Obesity (2014) 38, 456u2013465  Figure 6. Effects of the PPARd-agonist on adipogenic marker expression in adipose tissue in 2K1C animalsu2014treated with and without GW501516 or GW 501516u00feSnMP. (au2013d)  The actin blots are enlarged and aligned below. Contrast and brightness have been adjusted to make details more apparent. The duplication of this actin blot has been commented on previously in this forum. https: pubpeer.com publications BDEF6309C027A4C387F0C7CE279822  In the  mest panel in the blot in figure 6a, lanes 1-4 and 5-8 are duplicates; I added the numbering for reference. If one rotates lanes 1-4 180 degrees about horizontal axis and aligns them with lanes 5-8, their identity becomes apparent. The contrast and brightness of the enlarged images were adjust to make the shared features more apparent. It turns out that this is the same blot noted in one of the publications cited above (Obesity (Silver Spring). 2014 March, figure 7C) except that it is flipped left to right. https: pubpeer.com publications E865BFC0CEBB2DC7E479846587019D I feel dizzy.  ,