Association of decreased expression of the macrophage scavenger receptor MARCO with tumor progression and poor prognosis in human hepatocellular carcinoma

Background and Aim: The macrophage receptor with collagenous structure (MARCO) belongs to the scavenger receptor family; however, few studies have assessed their potentials in modulating inflammatory signaling other than the typical function of pattern recognition and phagocytic clearance. Interestingly, RNA-Seq analyses of hepatocellular carcinoma (HCC) have identified MARCO as one of the top 30 differentially expressed genes between cancerous and adjacent noncancerous tissues. However, no research has been performed to study MARCO in liver cancer. Methods: MARCO protein expression was evaluated by immunostaining liver tissue specimens collected from 88 HCC patients, 10 liver cirrhosis patients, 6 metastatic patients, and 5 healthy controls. All sections were reviewed by blinded observers followed by the interpretation of integral optical density per area as a measure of protein intensity. Results: We observed significantly decreased expression of MARCO in intratumoral tissues of HCC compared with expression in peritumoral tissues. The expression of MARCO declined progressively as the disease condition was aggravated, with the highest expression found in healthy controls and the lowest found in patients with HCC metastasis. Furthermore, MARCO expression decreased along with tumor progression. MARCO(+) cells co-localized with CD68(+) cells, indicating predominant expression on macrophages. The overall survival rate was significantly increased in patients with high intratumoral MARCO expression compared with that of patients with low intratumoral MARCO expression. Conclusions: Our study is the first to demonstrate an association between MARCO expression and the progression and prognosis of HCC.