Chaperonin CCT-mediated AIB1 folding promotes the growth of ERα-positive breast cancer cells on hard substrates
Authors: Ze Zhang
Jun Jang
Lingling Zhang
Li Chen
Xiangdong Luo
Juhui Qiu
Journal: PLoS ONE (2014)
Discipline: Multidisciplinary
Keywords: Estrogen receptor alpha; Bone metastases; Substrates; Chaperonin CCT; AIB1
Affiliations: Breast Disease Center, Southwest Hospital, Third Military Medical University, Chongqing, China; Burn Research Institute, Southwest Hospital, Third Military Medical University, Chongqing, China; National Key Laboratory of Trauma and Burns, Chongqing Key Laboratory of Disease Proteomics, Chongqing, China., Burn Research Institute, Southwest Hospital, Third Military Medical University, Chongqing, China; National Key Laboratory of Trauma and Burns, Chongqing Key Laboratory of Disease Proteomics, Chongqing, China., Breast Disease Center, Southwest Hospital, Third Military Medical University, Chongqing, China.

Abstract:  Clinical observations have revealed a strong association between estrogen receptor alpha (ERα)-positive tumors and the development of bone metastases, however, the mechanism underlying this association remains unknown. We cultured MCF-7 (ERα-positive) on different rigidity substrates. Compared with cells grown on more rigid substrates (100 kPa), cells grown on soft substrates (10 kPa) exhibited reduced spreading ability, a lower ratio of cells in the S and G2/M cell cycle phases, and a decreased proliferation rate. Using stable isotope labeling by amino acids (SILAC), we further compared the whole proteome of MCF-7 cells grown on substrates of different rigidity (10 and 100 kPa), and found that the expression of eight members of chaperonin CCT increased by at least 2-fold in the harder substrate. CCT folding activity was increased in the hard substrate compared with the soft substrates. Amplified in breast cancer 1 (AIB1), was identified in CCT immunoprecipitates. CCT folding ability of AIB1 increased on 100-kPa substrate compared with 10- and 30-kPa substrates. Moreover, using mammalian two-hybrid protein-protein interaction assays, we found that the polyglutamine repeat sequence of the AIB1 protein was essential for interaction between CCTζ and AIB1. CCTζ-mediated AIB1 folding affects the cell area spreading, growth rate, and cell cycle. The expressions of the c-myc, cyclin D1, and PgR genes were higher on hard substrates than on soft substrate in both MCF-7 and T47D cells. ERα and AIB1 could up-regulate the mRNA and protein expression levels of the c-myc, cyclin D1, and PgR genes, and that 17 β-estradiol could enhance this effects. Conversely, 4-hydroxytamoxifen, could inhibit these effects. Taken together, our studies demonstrate that some ERα-positive breast cancer cells preferentially grow on more rigid substrates. CCT-mediated AIB1 folding appears to be involved in the rigidity response of breast cancer cells, which provides novel insight into the mechanisms of bone metastasis. 

Retracted: Yes

PubPeer comments:
 The data in this manuscript do not support most of their conclusion. For exam, in figure3, they used TNF-a only to stimulate tenocytes to express inflammatory cytokines. However, they concluded that  The TNF-u03b1 and IL-20 Up-Regulated in de Quervain s Can Promote Inflammation Cytokine Release , where the IL-20 is? IL-20 was not used here to stimulate tenocytes. Furthermore, it s totally wrong to measure NF-kB by q-PCR to explain inflammation. Only if they investigate phosphorylated NF-KB by western blot in tenocytes treated with TNF-a could explain inflammation. There is no staining of IL-20 in primary tenocytes; and no control cell staining of their immunocytochemistry. ,