TGF-β2: A Novel Target of CD44-Promoted Breast Cancer Invasion

Abstract

We have developed a tetracycline (tet)-off regulated expression of CD44s gene in the breast cancer (BC) cell line MCF-7 (B5 clone) and identified TGF-β2 (Transforming Growth Factor beta-2; 3 fold induction) as a potential CD44-downstream transcriptional target by microarray analysis. To further validate this finding, the same RNA samples, used for microarray analysis and their corresponding protein lysates, collected from the BC cell line MCF-7-B5, were examined for CD44 expression in the presence of HA. Our results showed that TGF-β2 mRNA levels were significantly elevated following the removal of tetracycline at 18, 24, and 48 h post-HA stimulation compared to the parental cells. Furthermore, the TGF-β2 precursor protein increased in a time-dependent pattern upon HA-stimulation and in the absence of tetracycline. More interestingly, inhibition of CD44 gene by RNAi method decreased TGF-β2 expression upon HA-stimulation, and subsequently inhibited BC cell invasion in vitro. In addition to identifying TGF-β2 as a target for HA/CD44 signaling, this data suggests that ATF/CREB might be a potential transcription factor linking HA/CD44 activation to TGF-β2 transcription and additional experiments are required for a better understanding of the molecular mechanisms underpinning the novel function of the CD44/ TGF-β2 signaling pathway in breast cancer metastasis.

Role of the extracellular matrix in cancer‐associated epithelial to mesenchymal transition phenomenon

“…Notably, TGF‐β is a factor key to the preserving of the mesenchymal‐like phenotype in circulating cancer cells, due to CD44S isoform downstream signaling, which regulates vimentin and Smad2 levels (Mima et al, ) and as discussed by Heldin et al (). Furthermore, Ouhtit et al () suggest that HA/CD44s signaling, which initiates ATF/CREB activity, might facilitate TGF‐β2 transcription.…”

TGF-β1/PTEN/PI3K signaling plays a critical role in the anti-proliferation effect of tetrandrine in human colon cancer cells

“…Three sub-types of TGF-β are found in this family, including TGF-β1, TGF-β2 and TGF-β3. In reference to cancer, all the three isoforms of TGF-β are involved in cancer progression (22)(23)(24). For colon cancer, the dysfunction or loss of TGF-β signaling will promote progression of cancer (25,26).…”

HAS2 and CD44 in Breast Tumorigenesis

“…As shown in Table 8.1, basal-like cells that are highly metastatic exhibit high expression of CD44s. It has been demonstrated that although TGFβ signaling is the major regulator of EMT and maintains the stem cell phenotype (Scheel et al, 2011), CD44s, but not the variant isoforms, plays an important role in TGFβ-mediated mesenchymal phenotype associated with vimentin expression and high levels of Smad2 in nuclei (Mima et al, 2012;Ouhtit et al, 2013). Nevertheless, recent studies in our laboratory revealed that signals triggered via the binding of HAS2synthesized HA on bone-metastasizing breast cancer cells, to CD44 expressed by microvascular endothelial cells, promotes the adhesiveness between breast cancer cells and endothelial cells and thus cancer cell intravasation (Olofsson, Porsch, & Heldin, 2014).…”