Tumor-Specific Targeting of Pancreatic Cancer with Shiga Toxin B-Subunit

Abstract

Pancreatic carcinoma is one of the most aggressive tumor entities, and standard chemotherapy provides only modest benefit. Therefore, specific targeting of pancreatic cancer for early diagnosis and therapeutic intervention is of great interest. We have previously shown that the cellular receptor for Shiga toxin B (STxB), the glycosphingolipid globotriaosylceramide (Gb 3 or CD77) is strongly increased in colorectal adenocarcinoma and their metastases. Here, we report an upregulation of Gb 3 in pancreatic adenocarcinoma (21 of 27 cases) as compared with matched normal tissue (n ¼ 27). The mean expression was highly significantly increased from 30 AE 16 ng Gb 3 /mg tissue in normal pancreas to 61 AE 41 ng Gb 3 /mg tissue (mean AE SD, P ¼ 0.0006), as evidenced by thin layer chromatography. Upregulation of Gb 3 levels did not depend on tumor stage or grading and showed no correlation with clinical outcome. Tumor cells and endothelial cells were identified as the source of increased Gb 3 expression by immunocytochemistry. Pancreatic cancer cell lines showed rapid intracellular uptake of STxB to the Golgi apparatus, following the retrograde pathway. The therapeutic application of STxB was tested by specific delivery of covalently coupled SN38, an active metabolite of the topoisomerase I inhibitor irinotecan. The cytotoxic effect of the STxB-SN38 compound in pancreatic cancer cell lines was increased more than 100-fold compared with irinotecan. Moreover, this effect was effectively blocked by competing incubation with nonlabeled STxB, showing the specificity of the targeting. Thus, STxB constitutes a promising new tool for specific targeting of pancreatic cancer. Mol Cancer Ther; 10(10); 1918-28. Ó2011 AACR.

Gastric Adenocarcinomas Express the Glycosphingolipid Gb3/CD77: Targeting of Gastric Cancer Cells with Shiga Toxin B-Subunit

“…The nontoxic B-subunit of the bacterial Shiga toxin (STxB) may be used as an efficient and specific tool for tumor targeting. The cellular STxB receptor, the neutral glycosphingolipid globotriaosylceramide Gb 3 (Gala1-4Galb1-4Glcb1-1Cer), or CD77, is overexpressed in colon carcinoma (6,21), pancreatic (5,8), and breast cancer (25). Moreover, STxB can be functionalized and coupled to specific agents for noninvasive or endoscopic tumor imaging, which has successfully been demonstrated in preclinical models (28,36).…”

“…To avoid contamination and phenotype changes, cells were kept as frozen stocks and cultured consecutively for 4 weeks maximum in DMEM with FCS (7%), 1% penicillin/streptomycin, and 1% glutamine. Gastric cancer cell lines of diffuse/poorly differentiated type: AGS and KATO III, GP220 MKN-45 NUGC4, cell lines of intestinal type: MKN-7, NCI-N87, St 2957, St 3051, and St 23132, and HCT 116 colorectal cancer cells as described previously (8). Cell lines have been tested and authenticated by multiplex short tandem repeat analysis (Promega), the last test has been performed in October 2015 at the Institute of Legal Medicine, LMU Munich, Germany.…”

“…Samples were stained with fluorescently labeled STxB, according to methods established previously (8). In all cases, STxB-labeling was restricted to the abluminal parts of gastric glands, and no major differences were observed between different parts of the stomach.…”

“…[4][5][6][7][8]. The terminal disaccharide of this lipid is the receptor of the bacterial Shiga toxin.…”

“…The decisive requirement for application of STxB is the cellspecific expression of Gb 3 in tumor cells: Gb3 is expressed by Burkitt and centrofollicular lymphoma and solid tumors like testicular seminoma, breast, ovary, pancreatic, and colon cancer (5,6,8,(19)(20)(21)(22)(23)(24)(25)(26).…”