Exosomes in colorectal carcinoma formation: ALIX under the magnifying glass

• Published in: Modern pathology Vol. 29; no. 8; pp. 928 - 938
• Main Authors: Valcz, Gábor, Galamb, Orsolya, Krenács, Tibor, Spisák, Sándor, Kalmár, Alexandra, Patai, Árpád V, Wichmann, Barna, Dede, Kristóf, Tulassay, Zsolt, Molnár, Béla
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2016; Elsevier Limited
• Subjects: Adenoma - chemistry; Adenoma - genetics; Adenoma - pathology; Aged; Aged, 80 and over; Biomarkers, Tumor - analysis; Biomarkers, Tumor - genetics; Biopsy; Biosynthesis; Calcium-Binding Proteins - analysis; Calcium-Binding Proteins - genetics; Cancer; Carcinoma - chemistry; Carcinoma - genetics; Carcinoma - pathology; Case-Control Studies; Cell culture; Cell Cycle Proteins - analysis; Cell Cycle Proteins - genetics; Colorectal Neoplasms - chemistry; Colorectal Neoplasms - genetics; Colorectal Neoplasms - pathology; Endosomal Sorting Complexes Required for Transport - analysis; Endosomal Sorting Complexes Required for Transport - genetics; Exosomes - chemistry; Exosomes - genetics; Exosomes - pathology; Female; Gene Expression Profiling - methods; Growth factors; Humans; Immunohistochemistry; Male; Medical research; Medicine; Metastasis; MicroRNAs; Middle Aged; Multivesicular Bodies - chemistry; Multivesicular Bodies - genetics; Multivesicular Bodies - pathology; Oligonucleotide Array Sequence Analysis; Oncology; Pathology; Proteins; Smooth muscle; Stem cells; Tumor Microenvironment; Tumors; Hungary; United States > US
• ISSN: 0893-3952; 1530-0285
• DOI: 10.1038/modpathol.2016.72

Exosomes are small membrane vesicles that have important roles in transporting a great variety of bioactive molecules between epithelial compartment and their microenvironment during tumor formation including colorectal adenoma–carcinoma sequence. We tested the mRNA expression of the top 25 exosome-related markers based on ExoCharta database in healthy (n=49), adenoma (n=49) and colorectal carcinoma (n=49) patients using Affymetrix HGU133 Plus2.0 microarrays. Most related genes showed significantly elevated expression including PGK1, PKM, ANXA5, ENO1, HSP90AB1 and MSN during adenoma–carcinoma sequence. Surprisingly, the expression of ALIX (ALG 2-interacting protein X), involved in multivesicular body (MVB) and exosome formation, was significantly reduced in normal vs adenoma (P=5.02 × 10−13) and in normal vs colorectal carcinoma comparisons (P=1.51 × 10−10). ALIX also showed significant reduction (P<0.05) at the in situ protein level in the epithelial compartment of adenoma (n=35) and colorectal carcinoma (n=37) patients compared with 27 healthy individuals. Furthermore, significantly reduced ALIX protein levels were accompanied by their gradual transition from diffuse cytoplasmic expression to granular signals, which fell into the 0.6–2 μm diameter size range of MVBs. These ALIX-positive particles were seen in the tumor nests, including tumor–stroma border, which suggest their exosome function. MVB-like structures were also detected in tumor microenvironment including α-smooth muscle actin-positive stromal cells, budding off cancer cells in the tumor front as well as in cancer cells entrapped within lymphoid vessels. In conclusion, we determined the top aberrantly expressed exosome-associated markers and revealed the transition of diffuse ALIX protein signals into a MVB-like pattern during adenoma–carcinoma sequence. These tumor-associated particles seen both in the carcinoma and the surrounding microenvironment can potentially mediate epithelial–stromal interactions involved in the regulation of tumor growth, metastatic invasion and therapy response.