Date Published: February 15, 2019
Publisher: Public Library of Science
Author(s): Tuomas Kaprio, Tiina Rasila, Jaana Hagström, Harri Mustonen, Petri Lankila, Caj Haglund, Leif C. Andersson, Irina V. Lebedeva.
Ornithine decarboxylase (ODC) is the rate-limiting enzyme of polyamine synthesis. The two ODC antizyme inhibitors (AZIN1) and (AZIN2) are regulators of the catalytic activity of ODC. While AZIN1 is a regulator of cell proliferation, AZIN2 is involved in intracellular vesicle transport and secretion. There are no previous reports on the impact of AZIN2 expression in human cancer. We applied immunohistochemistry with antibodies to human AZIN2 on tissue micro- arrays of colorectal cancers (CRC) from 840 patients with a median follow-up of 5.1 years (range 0–25.8). The 5-year disease-specific survival rate was 58.9% (95% Cl 55.0–62.8%). High AZIN2 expression was associated with mucinous histology (p = 0.002) and location in the right hemicolon (p = 0.021). We found no association with age, gender, stage, or histological tumor grade. High tumor expression of AZIN2 predicted an unfavorable prognosis (p<0.0001, log-rank test), compared to low AZIN2 expression. Cox multivariable analysis identified AZIN2 as an independent factor of an unfavorable prognosis in CRC. The strongest AZIN2 expression was seen in invasive tumor cells having morphological features of epithelial-mesenchymal transition (EMT). Induction of EMT in HT-29 CRC cells lead to upregulated expression of endogenous AZIN2. Given that AZIN2 is a regulator of vesicle transport and secretion, we overexpressed human AZIN2 cDNA in T84 CRC cells, and found strongly enhanced accumulation of CD63-positive exosomes in the culture medium. These findings indicate that AZIN2 expression is a signature of EMT-associated secretory phenotype that is linked to an adverse prognosis in CRC.
Colorectal cancer (CRC), with over one million new cases every year, is one of the three most common cancers worldwide, and its incidence is rising. Early detection, radical surgery, and adjuvant chemotherapy are important for clinical outcome. Stage of disease at diagnosis is the most crucial factor for predicting patient outcome; 40% of the patients have localised disease and another 40% have regional disease. 
Cancers typically display increased catalytic activity of ODC and elevated concentrations of polyamines. AZIN1 and AZIN2 are both positive activators of ODC. AZIN1, which is physiologically involved in regulating the cell cycle and in stimulating cell proliferation, has been associated with cancer. Furthermore, it has been identified as a predictive factor of relapse in pediatric pre-B ALL  and associated with aggressive behavior in cancers of the breast, prostate, lung, and ovary .