CCN6 regulates IGF2BP2 and HMGA2 signaling in metaplastic carcinomas of the breast

Emily R McMullen; Maria E Gonzalez; Stephanie L Skala; Mai Tran; Dafydd Thomas; Sabra I Djomehri; Boris Burman; Kelley M Kidwell; Celina G Kleer

doi:10.1007/s10549-018-4960-2

CCN6 regulates IGF2BP2 and HMGA2 signaling in metaplastic carcinomas of the breast

Breast Cancer Res Treat. 2018 Dec;172(3):577-586. doi: 10.1007/s10549-018-4960-2. Epub 2018 Sep 15.

Authors

Emily R McMullen¹, Maria E Gonzalez^{1

2}, Stephanie L Skala¹, Mai Tran^{1

2}, Dafydd Thomas¹, Sabra I Djomehri^{1

2}, Boris Burman^{1

2}, Kelley M Kidwell^{2

3}, Celina G Kleer^{4

5

6}

Affiliations

¹ Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
² Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
³ Department of Biostatistics, University of Michigan Medical School, Ann Arbor, MI, 48109, USA.
⁴ Department of Pathology, University of Michigan Medical School, Ann Arbor, MI, 48109, USA. kleer@umich.edu.
⁵ Rogel Cancer Center, University of Michigan Medical School, Ann Arbor, MI, 48109, USA. kleer@umich.edu.
⁶ Department of Pathology, University of Michigan Medical School, 4217 Rogel Cancer Center, 1500 E. Medical Center Dr., Ann Arbor, MI, 48109, USA. kleer@umich.edu.

Abstract

Purpose: Metaplastic breast carcinomas are an aggressive subtype of triple-negative breast cancer (TNBC) in which part or all of the adenocarcinoma transforms into a non-glandular component (e.g., spindled, squamous, or heterologous). We discovered that mammary-specific Ccn6/Wisp3 knockout mice develop mammary carcinomas with spindle and squamous differentiation that share upregulation of the oncofetal proteins IGF2BP2 (IMP2) and HMGA2 with human metaplastic carcinomas. Here, we investigated the functional relationship between CCN6, IGF2BP2, and HMGA2 proteins in vitro and in vivo, and their expression in human tissue samples.

Methods: MMTV-cre;Ccn6^fl/fl tumors and spindle TNBC cell lines were treated with recombinant CCN6 protein or vehicle. IGF2BP2 was downregulated using shRNAs in HME cells with stable CCN6 shRNA knockdown, and subjected to invasion and adhesion assays. Thirty-one human metaplastic carcinomas were arrayed in a tissue microarray (TMA) and immunostained for CCN6, IGF2BP2, and HMGA2.

Results: CCN6 regulates IGF2BP2 and HMGA2 protein expression in MMTV-cre;Ccn6^fl/fl tumors, in MDA-MB-231 and - 468, and in HME cells. CCN6 recombinant protein reduced IGF2BP2 and HMGA2 protein expression, and decreased growth of MMTV-cre;Ccn6^fl/fl tumors in vivo. IGF2BP2 shRNA knockdown was sufficient to reverse the invasive abilities conferred by CCN6 knockdown in HME cells. Analyses of the TCGA Breast Cancer Cohort (n = 1238) showed that IGF2BP2 and HMGA2 are significantly upregulated in metaplastic carcinoma compared to other breast cancer subtypes. In clinical samples, low CCN6 is frequent in tumors with high IGF2BP2/HMGA2 with spindle and squamous differentiation.

Conclusions: These data shed light into the pathogenesis of metaplastic carcinoma and demonstrate a novel CCN6/IGF2BP2/HMGA2 oncogenic pathway with biomarker and therapeutic implications.

Keywords: Breast cancer; CCN6; HMGA2; IGF2BP2; Metaplastic; WISP3.

MeSH terms

Animals
CCN Intercellular Signaling Proteins / physiology*
Cell Adhesion
Cell Line, Tumor
Female
HMGA2 Protein / analysis
HMGA2 Protein / physiology*
Humans
Mice
Middle Aged
Neoplasm Invasiveness
Neoplasm Metastasis
RNA-Binding Proteins / analysis
RNA-Binding Proteins / physiology*
Signal Transduction / physiology*
Triple Negative Breast Neoplasms / pathology*
Triple Negative Breast Neoplasms / therapy

Substances

CCN Intercellular Signaling Proteins
CCN6 protein, human
HMGA2 Protein
IGF2BP2 protein, human
RNA-Binding Proteins

Abstract

MeSH terms

Substances

Grants and funding