SPINK1 Status in Colorectal Cancer, Impact on Proliferation, and Role in Colitis-Associated Cancer

Abstract

Colorectal cancer is a major cause of deaths due to cancer; therefore, research into its etiology is urgently needed. Although it is clear that chronic inflammation is a risk factor for colorectal cancer, the details remain uncertain. Serine protease inhibitor, Kazal type 1 (SPINK1) is mainly produced in pancreatic acinar cells. However, SPINK1 is expressed in various cancers and in inflammatory states, such as colon cancer and inflammatory bowel disease. There are structural similarities between SPINK1 and epidermal growth factor (EGF). Hence, it was hypothesized that SPINK1 functions as a growth factor for tissue repair in inflammatory states, and if prolonged, acts as a promoter for cell proliferation in cancerous tissues. Here, immunohistochemical staining for SPINK1 was observed in a high percentage of colorectal cancer patient specimens and SPINK1 induced proliferation of human colon cancer cell lines. To clarify its role in colon cancer in vivo, a mouse model exposed to the colon carcinogen azoxymethane and nongenotoxic carcinogen dextran sodium sulfate revealed that Spink3 (mouse homolog of SPINK1) is overexpressed in cancerous tissues. In Spink3 heterozygous mice, tumor multiplicity and tumor volume were significantly decreased compared with wild-type mice. These results suggest that SPINK1/Spink3 stimulates the proliferation of colon cancer cells and is involved in colorectal cancer progression.Implications: Evidence suggests that SPINK1 is an important growth factor that connects chronic inflammation and cancer.

Emerging Roles of SPINK1 in Cancer

“…These proteins have been suggested to function as tumor suppressors in CRC and their expression is downregulated in early stages of CRC (59 ). In a carcinogen-induced colitis and colon cancer mouse model, expression levels of SPINK3, the mouse ortholog of SPINK1, correlated with colitis and subsequent tumor burden, suggesting a link between SPINK3 and inflammation-induced colon cancer (56 ). These data support the role of SPINK1 as an oncogene and an acute-phase reactant in CRC.…”

“…Notably, in this model, SPINK1 inhibited the activation of caspase-dependent apoptosis (58 ). Forced expression of SPINK1 in HT-29 and Colo205 cells enhanced cell proliferation (56 ) and conversely stable knockdown of SPINK1 decreased proliferation of the HT-29 cell-derived cell line WiDr (59 ). Further, in the study by Chen and colleagues (54 ), SPINK1 positivity was correlated with a high proliferation rate, as measured by the Ki67 index.…”

“…In another recent study, SPINK1 was shown to be expressed in around 55% of colorectal tumors and significantly higher protein levels were observed in advanced tumors. However, no correlation between SPINK1 expression and overall survival was found (56 ). Hence the prognostic value of tissue expression of SPINK1 in colon cancer remains controversial.…”

Novel method to rescue a lethal phenotype through integration of target gene onto the X-chromosome

“…To this end, we generated a replacement vector containing CAG promoter-human SPINK1 minigene12 flanked by two mutated lox P sites, and co-transfected this vector along with a Cre recombinase expression vector13 into B210 ES cells (Fig. 1a).…”

“…SPINK1 minigene was described elsewhere12. For the present study, we have generated a replacement vector30 containing lox JTZ17-CAG-promoter (pCAGGS)- SPINK1 minigene-polyA (pA)- phosphoglycerate kinase-1 promoter (PGK)-puromycin resistance gene (PAC)-pA (PGK-PAC-pA)- lox 2272.…”