Determinants of differential liver-colonizing potential of variants of the MCA-38 murine colon cancer cell line

Liver and circulating NK1.1(+)CD3(-) cells are increased in infection with attenuated Salmonella typhimurium and are associated with reduced tumor in murine liver cancer

An attenuated (DeltacyA, Deltacrp) strain of Salmonella typhimurium (chi4550) containing a gene for human IL-2 (chi4550pIL2) reduces hepatic tumor burden when orally inoculated into mice with liver cancer; however, wild-type S. typhimurium is also associated with cancer regression. Therefore, experiments were designed to clarify the invasiveness and the anti-tumor properties of three strains of S. typhimurium. S. typhimurium chi4550pIL2, chi4550, or wild type (WT) was incubated with mature Caco-2 and HT-29 enterocytes, and S. typhimurium internalization was assessed. For infectivity experiments, mice were orally inoculated with saline or 10(9)S. typhimurium chi4550pIL2, chi4550, or WT; 48 h later mice were sacrificed for analysis of cecal bacteria and S. typhimurium translocation to mesenteric lymph nodes. For experiments involving tumor implantation, four groups were studied: saline control, tumor alone, chi4550pIL2+tumor, and chi4550+tumor. Mice were orally inoculated with saline or S. typhimurium and underwent laparotomy 24 h later with 5 x 10(4) MCA38 murine adenocarcinoma cells injected into the spleen. On day 14, liver tumors were counted and peripheral blood and hepatic lymphocyte populations were analyzed by FACScan. Attenuated S. typhimurium exhibited decreased internalization by cultured enterocytes and decreased infectivity after oral inoculation. Mice treated with chi4550pIL2 or chi4550 had fewer liver tumors and increased populations of hepatic and circulating NK1.1(+)CD3(-) lymphocytes compared to mice treated with saline (P < 0.01). These data suggest that attenuated S. typhimurium may have an application as an anti-tumor agent.

Correlation between the sialylation of cell surface Thomsen-Friedenreich antigen and the metastatic potential of colon carcinoma cells in a mouse model

The cell surface glycosylation profiles of a liver metastatic colon carcinoma variant cell line, SL4 cells previously selected from colon 38 cells in vivo for liver colonization were investigated. Flowcytometric analysis was performed with 7 plant lectins and 10 carbohydrate specific monoclonal antibodies. The results showed that peanut agglutinin (PNA), Sambucus nigra agglutinin, Ulex europeus agglutinin-I, anti-LeX, anti-LeY, and anti-Le(b) antibodies bound to the parental colon 38 cells but not to SL4 cells. Another variant cell line was selected in vitro for the paucity of cell surface PNA-binding sites using a magnetic cell sorter and was designated as 38-N4 cells. The binding profiles of plant lectins and carbohydrate-specific antibodies to 38-N4 cells were very similar to those of SL4 cells. After intrasplenic injections, metastatic ability of 38-N4 cells was higher than that of colon 38 cells. PNA binding to SL4 cells and 38-N4 cells was detected after sialidase treatment of these cells, indicating increased sialylation of Thomsen-Friedenreich antigen in these cells. The mRNA levels of sialyltransferases, ST3Gal I, ST3Gal II, ST6GalNAc I, and ST6GalNAc II, were compared. The level of ST3Gal II mRNA was elevated in both SL4 cells and 38-N4 cells, whereas the level of ST6GalNAc II mRNA was elevated in 38-N4 cells compared with colon 38 cells. According to the expression array analysis, there are other glycosyltransferase genes differentially expressed between SL4 and colon 38 cells, yet their involvement in the altered glycosylation in these cells is unclear.

Suppression of a sialyltransferase by antisense DNA reduces invasiveness of human colon cancer cells in vitro

Transfer of terminal alpha 2,6-linked sialic acids to N-glycans is catalyzed by beta-galactoside alpha 2,6-sialyltransferase (ST6Gal I). Expression of ST6Gal I and its products is reportedly increased in colon cancers. To investigate directly the functional effects of ST6Gal I expression, human colon cancer (HT29) cells were transfected with specific antisense DNA. ST6Gal I mRNA and protein were virtually undetectable in six strains of transfected HT29 cells. ST6Gal activity was reduced to 14% of control (P<0.005) in transfected cells. Expression of terminal alpha 2,6- and alpha 2,3-linked sialic acids, and unmasked N-acetyllactosamine oligosaccharides, respectively, was assessed using flow cytometry and fluoresceinated Sambucus nigra, Maackia amurensis and Erythrina cristagalli lectins. Results indicated a major reduction in expression of alpha 2,6-linked sialic acids and counterbalancing increase in unmasked N-acetyllactosamines in antisense DNA-transfected cells, without altered expression of alpha 2,3-linked sialic acids or ganglioside profiles. The ability of transfected cells to form colonies in soft agar and to invade extracellular matrix material (Matrigel), respectively, in vitro was reduced by approx. 98% (P<0.0001) and more than 3-fold (P<0.005) compared to parental HT29 cells. These results indicate that N-glycans bearing terminal alpha 2,6-linked sialic acids may enhance the invasive potential of colon cancer cells.

Inhibitory effects of bovine lactoferrin on colon carcinoma 26 lung metastasis in mice

In order to determine the effects of the multifunctional iron-binding glycoprotein, lactoferrin (LF), and related compounds on tumor growth and metastasis, bovine LF (bLF), and bLF hydrolysate and lactoferricin (bLFcin), active products generated by acid-pepsin hydrolysis were administered orally to BALB/c mice bearing subcutaneous (s.c.) implants of the highly metastatic colon carcinoma 26 (Co 26Lu). bLF and the bLF hydrolysate demonstrated significant inhibition of lung metastatic colony formation from s.c. implanted tumors without appreciable effects on tumor growth. bLFcin displayed a tendency for inhibition of lung metastasis. On the other hand, bLF did not exert marked anti-metastatic activity in athymic nude mice bearing Co 26Lu, though bLF had a tendency to inhibit the lung metastatic colony formation associated with anti-asialoGM1 antibody (Ab) treatment. AsialoGM1+ and CD8+ cells in white blood cells were increased after treatment with bLF. In vitro, the viability of Co 26Lu-F55 cells was markedly decreased when co-cultured with white blood cells from mice administrated bLF p.o., but recovered on treatment with anti-asialoGM1 Ab or anti-CD8 mAb and complement. The results suggest bLF and related compounds might find application as tools in the control of metastasis and that asialoGM1+ and CD8+ cells in the blood are important for their inhibitory effects.