Tumor growth-promoting cellular host response during liver atrophy after portal occlusion

BACKGROUND/AIMS

Clinical observations suggest cancer progression after preoperative segmental portal vein occlusion, a procedure to prevent liver failure after major hepatic resections. The aim of this study was to determine whether portal occlusion induces host reactions which promote cancer invasion and angiogenesis.

METHODS

The rat model of portal branch ligation (PBL) was compared with partial hepatectomy (PH) and sham operation (SO) and evaluated for the expression of heat shock protein-70 (hsp70), heme oxygenase-1 (hmox1), early growth response gene-1 (Egr-1) and urokinase-type plasminogen activator (uPA), its inhibitor (PAI-1) and receptor (uPAR).

RESULTS

Portal deprivation after PBL was associated with a regression of liver tissue to 25% of its original mass within 8 days with only modest fibrotic changes. During the progression of atrophy, there were significant inductions of hsp70-, hmox1- and Egr-1-mRNA in comparison with regenerating liver tissue. PAI-1-specific mRNA was transiently elevated at 3 - 48 h after PBL in the atrophying lobes, whereas uPA and uPAR were unaffected in comparison with PH or SO.

CONCLUSION

Hepatic atrophy caused by PBL is associated with increased expression of genes known to promote tumor growth. These host events represent a possible explanation for the tumor progression after portal occlusion and require further evaluation.

Sustained function in atrophying liver tissue after portal branch ligation in the rat

BACKGROUND

Preoperative segmental portal vein occlusion has become a common method to prevent liver failure after extended hepatic resection. To date, it is not elucidated whether atrophy by portal deprivation with concomitant contralateral regeneration leads to impaired liver function. We addressed this question by examining the expression of liver function proteins related to glucose homeostasis and acute-phase response in a corresponding animal model.

MATERIALS AND METHODS

Male Wistar rats were subjected to either portal branch ligation (PBL), partial hepatectomy (PH), or sham operation (SO). The mRNA expression and chronological distribution of glucose-6-phosphatase (G6P), glucagon receptor (GR), glceraldehyd-3-phosphate-dehydrogenase (GAPDH), albumin, fibronectin, and C1-esterase-inhibitor (C1-Inh) genes were examined by Northern-blot hybridizations. Determinations of serum-glucose and glycogen staining by periodic acid and Schiff were performed to analyze changes in glucose mobilization and storage.

RESULTS

In regenerating liver tissue after PH and PBL, we detected a selective reduction of transcripts encoding G6P during the prereplicative period 6 and 12 h after surgery and a contemporary drop in serum glucose levels. This impairment proved to be more distinct after PH than after PBL. Compared with the residual liver after PH, the level of glycogen disappearance was lower after PBL in the regenerating lobe. In the portal-deprived liver tissue, the expression of genes coding for G6P, GR, GAPDH, albumin, fibronectin, and C1-Inh was not altered compared with the SO group.

CONCLUSIONS

Overall, portal-deprived liver tissue undergoing atrophy retains its liver-specific differentiation and function and helps to maintain homeostasis during the fast regeneration of the non-occluded liver lobe.