Stathmin Is Required for Normal Mouse Mammary Gland Development and Δ16HER2-Driven Tumorigenesis

Abstract

Postnatal development of the mammary gland relies on the maintenance of oriented cell division and apicobasal polarity, both of which are often deregulated in cancer. The microtubule (MT) network contributes to control these processes; however, very little is known about the impact of altered MT dynamics in the development of a complex organ and on the role played by MT-interacting proteins such as stathmin. In this study, we report that female stathmin knockout (STM KO) mice are unable to nurse their litters due to frank impairment of mammary gland development. In mouse mammary epithelial cells, loss of stathmin compromised the trafficking of polarized proteins and the achievement of proper apicobasal polarity. In particular, prolactin receptor internalization and localization was altered in STM KO mammary epithelial cells, leading to decreased protein stability and downmodulation of the Prl/PrlR/STAT5 signal-ing pathway. Absence of stathmin induced alterations in mitotic spindle orientation, accumulation of mitotic defects, and apoptosis, overall contributing to tissue disorganization and further decreasing the expansion of the mammary epithelial compartment. Loss of stathmin in MMTV-D16HER2 transgenic mice decreased the incidence and increased the latency of these very aggressive mammary carcinomas. Collectively, these data identify the essential mammary protein stathmin as protumorigenic and suggest it may serve as a potential therapeutic target in breast cancer. Significance: Stathmin expression is critical to maintain oriented cell division and apicobasal polarity in normal mammary glands and to establish a protumorigenic program that eventually sustains HER2-positive breast cancer formation in mice.

Splicing factor proline- and glutamine-rich (SFPQ) protein regulates platinum response in ovarian cancer-modulating SRSF2 activity

“…GEP were performed essentially as described [20,39]. Briefly, 150 ng of total RNA were labeled with Cyanine (Cy)-3 dye andCy3-labeled RNA was hybridized using the Affymetrix Human Whole Genome (8 × 60 k) oligomicroarray platform (Agilent Technologies) and analyzed with an Agilent Microarray Scanner (Agilent Technologies) using the Agilent Feature Extraction Software 10.7.3 (Agilent Technologies).…”

CDKN1B mutation and copy number variation are associated with tumor aggressiveness in luminal breast cancer

“…Growth curves, cell cycle distribution by fluorescence-activated cell sorting (FACS) analysis, anchorage-independent cell growth and threedimensional (3D) mammary epithelial cell growth were determined as described previously [29][30][31][32][33]. Multiple cell clones were always tested in each assay, in duplicates or triplicates as appropriate.…”

“…All analyses were performed as described previously [28][29][30]32,33] and are described in detail in supplementary material, Supplementary materials and methods. For the analysis of protein stability, cycloheximide (Merck Life Science) was added to cell culture medium at 10 μg/ml and cells were collected at the indicated times and processed to prepare protein lysates for western blot analyses.…”

RNA splicing alteration in the response to platinum chemotherapy in ovarian cancer: A possible biomarker and therapeutic target

“…The AS of ERBB2 gene (encoding for HER2) can induce the exclusion of exon 16, leading to the production and coexpression with the full‐length HER2 of the so‐called Δ16HER2 isoform 32,33 . Δ16HER2 displays higher receptor dimerization, increased resistance to the most common anti‐HER2 therapy, trastuzumab, in vitro, and increased transforming and metastatic ability in vivo 32,34–36 . It is worth noting also the exon 6 inclusion of the MDM4 that results in MDM4 overexpression and p53 degradation in cancer since this AS has been targeted with specific antisense oligonucleotides (ASOs) to reduce cancer cell growth, both in vitro and in vivo 37 …”

“…32,33 Δ16HER2 displays higher receptor dimerization, increased resistance to the most common anti-HER2 therapy, trastuzumab, in vitro, and increased transforming and metastatic ability in vivo. 32,[34][35][36] It is worth noting also the exon 6 inclusion of the MDM4 that results in MDM4 overexpression and p53 degradation in cancer since this AS has been targeted with specific antisense oligonucleotides (ASOs) to reduce cancer cell growth, both in vitro and in vivo. 37 The use of mutually exclusive exons ( Figure 1C) is a rare form of AS, which affects only ∼1% of transcripts.…”