Characteristics of CD44 alternative splice pattern in the course of human colorectal adenocarcinoma progression

Abstract

BackgroundCD44 is considered as ‘a’ metastasis associated gene, despite the fact that it is an umbrella term for a group of molecules produced from a single gene by alternative splicing. However, little consideration is given to the above in the literature of colorectal carcinomas as well as other tumour types, leading to confusion and contradictory results about its possible role in tumour progression.MethodsWe compared the CD44 alternative splice pattern (ASP) of three genetically different human colorectal cancer cell lines (HT25, HT29, HCT116) using a series of PCR reactions and next- generation sequencing method, as well as identified a colorectal adenocarcinoma specific CD44 ASP. This ASP was further investigated in terms of its qualitative and quantitative stability in our experimental iso- and xenograft mouse models for colorectal cancer progression. A complex preclinical experimental set-up was established to separately test the different steps of tumour progression and the role of tumour microenvironment, respectively, focusing on the role of ‘CD44’ in this process.ResultsWe managed to present a colorectal cancer-specific CD44 ASP, which remained unchanged from cell lines throughout primary tumour formation and metastatic progression. Furthermore, we report a unique roster of all expressed CD44 variant isoforms characteristic to colorectal cancer. Finally, on quantitative assessment of the variable exons v3 and v6, higher co-expression levels were found to be characteristic to metastatically potent tumour cells.ConclusionParticular CD44 variant isoforms seem to act as “metastasis genes” via tumour microenvironment-driven shifts in v3 and v6 expressions. However, this function may just affect a minority of tumour subclones. This fact and the huge potential number of different CD44 splice variants that can contain v3 and v6 domains can explain incoherence of clinical studies regarding functional asessment of CD44 variants, as well as diminish the chances of using CD44 variants for predictive purpose.

CD44: A Multifaceted Molecule in Cancer Progression

“…A similar finding was also observed in glioma mouse model suggesting the importance of CD44 in cancer stemness [8]. Some recent studies have exhibited CD44 as cancer stem cell marker in breast, gastric, pancreatic, colorectal and other cancers [9][10][11][12][13][14][15][16][17]. Different tumor types and their associated cells in the microenvironment express probably different sets of CD44 isoforms with a varied combination of variants.…”

Activation of c-Met and Upregulation of CD44 Expression Are Associated with the Metastatic Phenotype in the Colorectal Cancer Liver Metastasis Model

“…The expression of key proteins in the CD44, β-catenin, and FAK pathways, which play an important role in CRC metastasis [7]–[9] was analyzed next. We observed a gradual increase of high molecular weight CD44 expression observed at ∼150 kDa in HT29 LM cell lines, with maximum CD44 expression in HT29 LM3 compared to the parental HT29 cell line ( Figure 3A ) .…”

CD44 Standard Isoform; Not a Good Marker for Colon Cancer

“…These discrepancies may be due to different patient material and follow up duration, antibodies, and immunohistochemical techniques used in different studies (2,9). Furthermore, a number of studies have demonstrated CD44 expression in most non-tumoral epithelial tissues, including stomach mucous membrane, small intestinal, prostate, ductal epithelium of breast, skin, hair follicles, and transitional epithelium (1, 2, 9).…”

“…In developed countries, colorectal cancer (CRC), or rather its progression to metastatic disease, accounts for 25% of tumor deaths (2). CRC evolves through a series of morphologically recognizable stages, known as the adenoma-carcinoma sequence.…”