Abstract
BackgroundIntelectin (ITLN) is an adipokine with two homologs—ITLN1 and ITLN2—that has various physiological functions. Studies analyzing the relationship between ITLN and cancer are focused on ITLN1; the available literature on ITLN2 and cancer is limited. This review aims to evaluate the role of ITLN1 in cancer without imposing any inclusion criteria, to examine pro- and anticancer roles for ITLN1 and to discuss whether the relationship between ITLN and cancer is mediated by obesity.FindingsOverall, ITLN1 level was highly variable in cancer patients but different from healthy individuals. Compared with control groups, patients with gastrointestinal and prostate cancer showed increased concentrations of circulating ITLN1, while patients with gynecological, breast, bladder, and renal cancer had lower ITLN1 levels. Several studies also evaluated tissue and tumor expression of ITLN1. In gastrointestinal cancer, ITLN1 was increased in tumor tissue compared with adjacent healthy tissue and elevated in the visceral adipose tissue of patients compared with controls. Consequently, the high levels of circulating ITLN1 might be determined by the tumor and by the cancer-associated weight loss in gastrointestinal cancer. ITLN1 can activate the phosphoinositide-3-kinase-protein kinase B/Akt (PI3K/Akt) pathway. The improper regulation of this pathway may contribute to a series of cellular events that favor tumor development and progression. Obesity has been linked with an increased risk of developing some cancers. Indeed, low circulating ITLN1 levels may be a marker of the metabolic effects of obesity, rather than obesity per se, and might contribute to a deregulation of the PI3K/Akt pathway.ConclusionsITLN1 could be associated with cancer formation and progression. Since circulating ITLN1 levels are highly variable and differ between cancer types, the local tumor production of ITLN1 could be more relevant in determining malignant behavior. Future research should aim to identify the source of ITLN1 variability, to understand the differences in ITLN1 between distinct tumor types, and to further explore the signaling pathways through which this adipokine influences cancer biology.
Highlights
Intelectin (ITLN), known as omentin, is a 34-kDa lectin that contains a fibrinogen-like domain and a unique intelectinspecific region that makes it distinct from other immune lectins [1, 2]
We recently identified ITLN1 and ITLN2 mRNA as increased in the visceral adipose tissue of gastrointestinal cancer patients and found that local but not circulating ITLN1 protein demonstrated a relationship with cancer cachexia [11]
A recent systematic review examining circulating ITLN1 levels in cancer found that ITLN1 was often increased in individuals with colorectal cancer compared with healthy controls [12]
Summary
Intelectin (ITLN), known as omentin, is a 34-kDa lectin that contains a fibrinogen-like domain and a unique intelectinspecific region that makes it distinct from other immune lectins [1, 2]. ITLN1 expression has been found in epicardial fat, the small intestine, colon, ovary, lungs, and renal collecting tubes, whereas ITLN2 is expressed in intestinal Paneth cells [2, 4, 5]. Both ITLN homologs can bind microbial glycan chains but not human glycans, and the adipokine may have a role in antimicrobial defense [2, 6]. Studies analyzing the relationship between ITLN and cancer are focused on ITLN1; the available literature on ITLN2 and cancer is limited. This review aims to evaluate the role of ITLN1 in cancer without imposing any inclusion criteria, to examine pro- and anticancer roles for ITLN1 and to discuss whether the relationship between ITLN and cancer is mediated by obesity
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