Effects of tirapazamine on experimental colorectal liver metastases after radiofrequency ablation1

Liposome quercetin enhances the ablation effects of microwave ablation in treating the rabbit VX2 liver tumor model

OBJECTIVE

This study aimed to investigate whether liposomal quercetin (LQ) could enhance the effects of microwave ablation (MVA) in treating the rabbit VX2 liver tumor model.

METHODS

Rabbits with VX2 liver tumors were randomly divided into three groups: intravenous LQ group (LQ group), MWA group and LQ combined with MWA (LQ + MWA) group. Five rabbits were randomly selected and sacrificed from each group at 12 h and on days 3, 7 and 14 of the operation. The tumor samples were detected and quantified by immunohistochemistry, Western blot, and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

For up to 7 days, the coagulation necrosis volume (CV) of the LQ + MWA group was larger than that of MWA and LQ groups (p < 0.05). Fourteen days after the operation, the total tumor volume of the LQ + MWA group was smaller than that of the LQ group and the MWA group (p < 0.05). The survival time of the LQ + MWA group was significantly longer than that of the MWA and LQ groups (p < 0.01). Heat shock protein 70 (HSP70), hypoxia inducible factor-1 α (HIF-1 α), vascular endothelial growth factor (VEGF), tumor microvessel density (MVD) were lower in the LQ + MWA group than the MWA and LQ groups at 12 h, on days 3 and 7. At hour 12 and on days 3 and 7, HSP70 mRNA and HIF-1α mRNA expression of MWA group were significantly higher than that of the LQ and LQ + MWA groups (p < 0.001). At 12 h, and on days 3 and 7, apoptotic rate of tumor cells in LQ + MWA group was higher than that of the MWA and LQ groups (p < 0.05). At 12 h and on days 3, 7 and 14, the proliferation index of tumor cells in residual tumor in LQ + MWA group was lower than that in the MWA and LQ groups (p < 0.05).

CONCLUSION

Preoperative infusion of LQ can significantly enhance the MWA effects of liver VX2 tumor, inhibit the excessive proliferation of residual tumor and angiogenesis, and decrease metastasis and prolong the survival period of experimental animals.

Targeting Hypoxia: Hypoxia-Activated Prodrugs in Cancer Therapy

Hypoxia is an important characteristic of most solid malignancies, and is closely related to tumor prognosis and therapeutic resistance. Hypoxia is one of the most important factors associated with resistance to conventional radiotherapy and chemotherapy. Therapies targeting tumor hypoxia have attracted considerable attention. Hypoxia-activated prodrugs (HAPs) are bioreductive drugs that are selectively activated under hypoxic conditions and that can accurately target the hypoxic regions of solid tumors. Both single-agent and combined use with other drugs have shown promising antitumor effects. In this review, we discuss the mechanism of action and the current preclinical and clinical progress of several of the most widely used HAPs, summarize their existing problems and shortcomings, and discuss future research prospects.

Effect of a hypoxic microenvironment after radiofrequency ablation on residual hepatocellular cell migration and invasion

Clinical observations have shown that the boundary of tumor ablation is often less than safe border and that the use of radiofrequency ablation (RFA) in the treatment of hepatocellular carcinoma (HCC) may probably accelerate its recurrence and metastasis. RFA can cause the formation of a transition zone between normal liver tissues and necrotic coagulation, where blood stagnation and thrombosis expose residual cancer cells to a hypoxic microenvironment. As the blocked vessels are slowly reperfused, the oxygen supply is gradually restored. Here, HCC cells underwent heat treatment and were cultured under hypoxic conditions to mimic the aforementioned situation, and morphological changes were observed in the surviving cells. Compared with their parental cells, hypoxic HCC cells showed changes that include enhanced invasive, metastatic, and chemoresistant abilities as well as mesenchymal characteristics. There was also a higher percentage of stem-like cells. However, either improving the hypoxic microenvironment or silencing hypoxia inducible factor (HIF)-1α signaling significantly reduced the invasive, metastatic, and chemoresistant potential and reversed the epithelial-mesenchymal transition to varying degrees. Together, these results indicated that a sustained hypoxic microenvironment after RFA may exert a negative impact on the prognosis of HCC patients, and minimizing exposure to a hypoxic microenvironment and targeting HIF-1α signaling might be effective strategies for patients who experience insufficient RFA therapy.

Recurrence location after resection of colorectal liver metastases influences prognosis

AIM

To assess the impact of first recurrence location on survival following surgery of colorectal liver metastases.

METHODS

A total of 265 consecutive patients with colorectal liver metastases undergoing liver surgery (2000-2011) were categorized according to first site of tumor recurrence. Time to recurrence (TTR) and overall survival (OS) were determined. Uni- and multivariate analysis were performed to identify factors associated with TTR and OS.

RESULTS

Median TTR was 1.16 years following liver resection, and 0.56 years following radiofrequency ablation (RFA). Intrahepatic recurrence following liver resection resulted in a significantly shorter median TTR compared to extrahepatic recurrence. Intrapulmonary recurrence was associated with superior survival compared to other recurrence locations. Such patterns were not observed in the RFA-treated group. Multivariate analysis identified the type of surgical treatment and extra-hepatic first-site recurrence (other than lung) as independent predictors for OS. Pre-operative chemotherapy and simultaneous intrahepatic and extrahepatic recurrence were independent predictors for both TTR and OS.

CONCLUSIONS

Patients with intrahepatic recurrence following liver resection have a significantly shorter TTR and OS when compared to patients developing extrahepatic recurrence. Pulmonary recurrence following resection is associated with longer survival. Simultaneous intra- and extrahepatic recurrence is an independent prognostic factor for TTR and OS.