Establishment of a hepatocyte cell line producing growth-promoting factors for liver-colonizing tumor cells

In vivo and in vitro interactions between human colon carcinoma cells and hepatic stellate cells

Stromal reaction is important for the growth of cancer both in primary and metastatic sites. To demonstrate this reaction during the hepatic metastasis of human colon carcinoma, we histologically investigated alterations to the distribution and phenotype of hepatic stellate cells (HSCs), the only mesenchymal cells in the liver parenchyma, using a nude mouse model. Intrasplenically injected colon carcinoma LM-H3 cells migrated into the space of Disse and underwent proliferation, in close association with hepatocytes and HSCs, at 2 days. At 14 days, HSCs were accumulated around the tumor mass and expressed alpha-smooth muscle actin, a marker for HSC activation. We next investigated in vitro the growth factors involved in the interactions between LM-H3 cells and HSCs. Conditioned medium of rat HSCs which underwent culture-induced activation contained platelet-derived growth factor (PDGF)-AB, hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta, and could augment LM-H3-cell proliferation and migration. Neutralizing antibodies against PDGF-AA and PDGF-BB and those against PDGF-BB and HGF inhibited proliferation and migration, respectively, of LM-H3 cells, whereas antibody against TGF-beta had no effect. LM-H3 cells expressed PDGF receptors-alpha and -beta and c-met. Conditioned medium of LM-H3 cells contained PDGF-AB, and could enhance HSC proliferation and migration. This augmenting effect was suppressed by treatment with anti-PDGF-AB antibody. The present study has demonstrated that bidirectional interactions involving PDGF and HGF take place in vitro between colon carcinoma cells and HSCs, raising the possibility that similar interactions might be involved in the stromal reaction during hepatic metastasis.

Ultrastructure of early phase hepatic metastasis of human colon carcinoma cells with special reference to desmosomal junctions with hepatocytes

To demonstrate ultrastructural events in the early phase of hepatic metastasis of human colon carcinoma, we intrasplenically injected a highly metastasizable, human colon carcinoma cell line LM-H3 (1 x 10(6) cells) into nude mice, and electron microscopically investigated the hepatic metastasis. At 24 h, tumor cells adhered to the endothelial wall of terminal portal venules and periportal sinusoids. At 48-72 h, after extravasation, they deeply invaded the hepatic cell plate and the interstitial tissue of the portal tract, in which they underwent proliferation and made the metastatic foci. Tumor cells were linked with each other or with surrounding hepatocytes by desmosomes. Desmosomes were maintained during the mitosis. When invading tumor cells were exposed to the bile canaliculi, they generated microvilli on the surface. Microvilli were also formed at the luminal surface of intracytoplasmic inclusions. In the interstitial tissue of the portal tract, tumor cells were closely associated with fibroblasts. However, no junctional specializations were seen between them. The present study demonstrated that human colon carcinoma cell line LM-H3 formed desmosomes with hepatocytes soon after invasion of the hepatic cell plate, suggesting the regulatory role of an interaction with hepatocytes in the growth of metastatic foci within the liver parenchyma.

CD44H participates in the intrahepatic growth of murine colon 26 adenocarcinoma cells

The purpose of this study was to determine if CD44, a metastasis-associated cell adhesion molecule, is involved in the hepatic colonization by murine colon 26 adenocarcinoma cells. Indirect membrane immunofluorescence and FACS analysis showed strong expressions of CD44 and integrin beta 1 on colon 26 cells. Injection of 1 x 10(5) colon 26 cells into the superior mesenteric vein of syngeneic BALB/c mice produced macroscopic hepatic nodules in 92% (22/24) of the mice 14 days after inoculation. When colon 26 cells were pretreated with an anti-CD44 monoclonal antibody (mAb), IM7, only 30% (3/10) of the mice produced minute nodules in the liver on day 14 (P < 0.001), though IM7 did not inhibit growth of the cells in vitro. Pretreatment of colon 26 cells with an anti-integrin beta 1 mAb did not significantly block the hepatic metastasis. Histologically, microcolonies of tumor cells were detected in all of the livers on day 14 including the IM7-pretreatment mice that were free of gross nodules. However, percentages of tumor-occupied areas in the liver were consistently lower in IM7-pretreatment mice than in control mice (0.82% vs. 5.0% on day 14; P < 0.005). Reverse transcription-polymerase chain reaction (RT-PCR) amplification of mRNA revealed that colon 26 cells and splenocytes only expressed the hematopoietic isoform of CD44 (CD44H), which had no insertion of variant exons, while normal colonocytes expressed possible variant isoforms. These data suggest that malignant transformation of murine colonic epithelium altered the expression pattern of CD44 isoforms and that CD44H participates in the intrahepatic growth of colon 26 cells.