Accelerated perinecrotic outgrowth of colorectal liver metastases following radiofrequency ablation is a hypoxia-driven phenomenon

Hepatic Radiofrequency Ablation-induced Stimulation of Distant Tumor Growth Is Suppressed by c-Met Inhibition

PURPOSE

To elucidate how hepatic radiofrequency (RF) ablation affects distant extrahepatic tumor growth by means of two key molecular pathways.

MATERIALS AND METHODS

Rats were used in this institutional animal care and use committee-approved study. First, the effect of hepatic RF ablation on distant subcutaneous in situ R3230 and MATBIII breast tumors was evaluated. Animals were randomly assigned to standardized RF ablation, sham procedure, or no treatment. Tumor growth rate was measured for 3½ to 7 days. Then, tissue was harvested for Ki-67 proliferative indexes and CD34 microvascular density. Second, hepatic RF ablation was performed for hepatocyte growth factor (HGF), vascular endothelial growth factor (VEGF), and c-Met receptor expression measurement in periablational rim, serum, and distant tumor 24 hours to 7 days after ablation. Third, hepatic RF ablation was combined with either a c-Met inhibitor (PHA-665752) or VEGF receptor inhibitor (semaxanib) and compared with sham or drug alone arms to assess distant tumor growth and growth factor levels. Finally, hepatic RF ablation was performed in rats with c-Met-negative R3230 tumors for comparison with the native c-Met-positive line. Tumor size and immunohistochemical quantification at day 0 and at sacrifice were compared with analysis of variance and the two-tailed Student t test. Tumor growth curves before and after treatment were analyzed with linear regression analysis to determine mean slopes of pre- and posttreatment growth curves on a per-tumor basis and were compared with analysis of variance and paired two-tailed t tests.

RESULTS

After RF ablation of normal liver, distant R3230 tumors were substantially larger at 7 days compared with tumors treated with the sham procedure and untreated tumors, with higher growth rates and tumor cell proliferation. Similar findings were observed in MATBIII tumors. Hepatic RF ablation predominantly increased periablational and serum HGF and downstream distant tumor VEGF levels. Compared with RF ablation alone, RF ablation combined with adjuvant PHA-665752 or semaxanib reduced distant tumor growth, proliferation, and microvascular density. For c-Met-negative tumors, hepatic RF ablation did not increase distant tumor growth, proliferation, or microvascular density compared with sham treatment.

CONCLUSION

RF ablation of normal liver can stimulate distant subcutaneous tumor growth mediated by HGF/c-Met pathway and VEGF activation. This effect was not observed in c-Met-negative tumors and can be blocked with adjuvant c-Met and VEGF inhibitors.

Insufficient radiofrequency ablation promotes the growth of non-small cell lung cancer cells through PI3K/Akt/HIF-1α signals

Accelerated progression of residual non-small cell lung cancer (NSCLC) after incomplete radiofrequency ablation (RFA) has frequently been reported. In this study, NSCLC cells A549, CCL-185, and H358 were treated using a water bath at 47°C for 5, 10, 15, 20, and 25 min gradually to establish the sublines A549-H, CCL-185-H, and H358-H, respectively. A549-H, CCL-185-H, and H358-H cells showed a significant increase in proliferation rate when compared with their corresponding parental cellsin vitro The expression of hypoxia-inducible factor-1α (HIF-1α) was obviously upregulated in both A549-H and CCL-185-H cells. Silencing of HIF-1α abolished the insufficient RFA-induced proliferation in A549-H and CCL-185-H cells. Furthermore, insufficient RFA treatment markedly elevated the phosphorylation of ERK1/2 and Akt, but not of p38 MAPK or JNK, in A549-H and CCL-185-H cells. The inhibitor of Akt, LY294002, but not the inhibitor of ERK1/2, PD98059, suppressed the upregulation of HIF-1α and the proliferation of A549-H and CCL-185-H cellsin vitro Thein vivoresults confirmed that insufficient RFA could trigger the tumor growth, upregulate the HIF-1α expression, and activate Akt in A549 xenograft tumors. Our data suggest that insufficient RFA can promote thein vitroandin vivogrowth of NSCLC via upregulating HIF-1α through the PI3K/Akt signals.

Thermal Ablative Therapies and Immune Checkpoint Modulation: Can Locoregional Approaches Effect a Systemic Response?

Percutaneous image-guided ablation is an increasingly common treatment for a multitude of solid organ malignancies. While historically these techniques have been restricted to the management of small, unresectable tumors, there is an expanding appreciation for the systemic effects these locoregional interventions can cause. In this review, we summarize the mechanisms of action for the most common thermal ablation modalities and highlight the key advances in knowledge regarding the interactions between thermal ablation and the immune system.

Irreversible Electroporation versus Radiofrequency Ablation: A Comparison of Local and Systemic Effects in a Small-Animal Model

Purpose To compare both periablational and systemic effects of two mechanistically different types of ablation: thermal radiofrequency (RF) ablation and electroporative ablation with irreversible electroporation (IRE) in appropriately selected animal models. Materials and Methods Animal experiments were performed according to a protocol approved by the Animal Care Committee of Hebrew University. Female C57BL/6 mice (n = 165) were randomized to undergo either RF or IRE ablation of noncancerous normal liver. The inflammatory response, cell proliferation, interleukin 6 (IL-6) levels, and intactness of vessels in the liver were assessed at 6, 12, and 24 hours and at 3, 7, and 14 days after ablation (n = 122 for mechanistic experiments). Systemic effects were then assessed by comparing tumor formation in an Mdr2-knockout (KO) mouse model (n = 15) and tumor growth in a remote BNL 1ME hepatoma xenograft tumor (n = 28). Results were averaged and evaluated by using two-tailed t tests. Results Although RF ablation was associated with a well-defined periablational inflammatory rim, for IRE, the infiltrate penetrated the ablation zone, largely along persistently patent vessels. Peak IL-6 levels (6 hours after ablation) were 10 and three times higher than at baseline for IRE and RF, respectively (P < .03). Mdr2-KO mice that were treated with IRE ablation had more tumors that were 3 mm or larger than mice treated with RF ablation or sham operation (mean, 3.6 ± 1.3 [standard deviation] vs 2.4 ± 1.1 and 2.2 ± 0.8, respectively; P < .05 for IRE vs both RF ablation and sham operation). For BNL 1ME tumors, both RF and IRE liver ablation reduced tumor growth, with a greater effect noted for IRE (1329 mm(3) ± 586 and 819 mm(3) ± 327 vs 2241 mm(3) ± 548 for sham operation; P < .05) that was accompanied by more infiltrating lymphocytes compared with sham operation (7.6 cells per frame ± 1.9 vs 11.2 ± 2.1 vs 0.3 ± 0.1; P < .05). Conclusion Persistent patency of vasculature within the coagulated zone from IRE increases the area and accumulation of infiltrative cells that is associated with a higher serum IL-6 level than RF ablation. These local changes of IRE induce more robust systemic effects, including both tumorigenic and immunogenic effects. (©) RSNA, 2016 Online supplemental material is available for this article.

Local recurrence of small cell lung cancer following radiofrequency ablation is induced by HIF-1α expression in the transition zone

Local recurrence of lung cancer following radiofrequency ablation (RFA) treatment is common. The aims of the present study were to assess how RFA treatment affects the growth of small cell lung cancer (SCLC) micrometastases in the transition zone (TZ) surrounding the ablated region and in the reference zones (RZs) of the ablated or unablated lobes and to identify the molecular mechanism(s) of lung cancer recurrence following RFA treatment. After lung micrometastases of human SCLCs had formed, RFA treatment was applied to the right upper lobe (RUL) of the lung in nude mice. Hypoxia inducible factor (HIF)-1α expression, proliferation and angiogenesis potential both in the TZ and RZ were evaluated over time. Separately, at day 1, 7 and 14 following RFA treatment, the growth of micrometastases showed an ~2-fold increase in the TZ compared to the RZ of the unablated lobe, as the right lower lobe (RLL) and the growth of micrometastases in the RZ of the RUL was also induced by RFA. In addition, accelerated tumor growth in the TZ was induced by HIF-1α, but was not associated with tissue angiogenesis potential. We concluded that local recurrences of SCLCs caused by overproliferation of micrometastases following RFA treatment were driven by HIF-1α, although angiogenesis was not the driving force in the TZ.

Sorafenib suppresses the epithelial-mesenchymal transition of hepatocellular carcinoma cells after insufficient radiofrequency ablation

BACKGROUND

Epithelial-mesenchymal transition (EMT) played an important role in the progression of hepatocellular carcinoma (HCC) after insufficient radiofrequency ablation (RFA). However, whether sorafenib could be used to suppress the EMT of HCC after insufficient RFA and further prevent the progression of residual HCC remains poorly unknown.

METHODS

Insufficient RFA was simulated using a water bath (47 °C 5, 10, 15, 20 and 25 min gradually). MTT assay and transwell assay were used to evaluate the effects of sorafenib on viability, migration and invasion of HepG2 and SMMC7721 cells after insufficient RFA in vitro. After insufficient RFA, the molecular changes in HCC cells with the treatment of sorafeinb were evaluated using western blot and ELISAs. An ectopic nude mice model was used to evaluate the effect of sorafenib on the growth of HepG2 cells in vivo after insufficient RFA.

RESULTS

HepG2 and SMMC7721 cells after insufficient RFA (named as HepG2-H and SMMC7721-H) exhibited enhanced viability, migration and invasion in vitro. Sorafenib inhibited the enhanced viability, migration and invasion of HepG2 and SMMC7721 cells after insufficient RFA. Molecular changes of EMT were observed in HepG2-H and SMMC7721-H cells. Sorafenib inhibited the EMT of HepG2-H and SMMC7721-H cells. HepG2-H cells also exhibited larger tumor size in vivo. Higher expression of PCNA, Ki67, N-cadherin, MMP-2 and MMP-9, was also observed in HepG2-H tumors. Sorafenib blocked the enhanced growth of HepG2 cells in vivo after insufficient RFA.

CONCLUSIONS

Sorafenib inhibited the EMT of HCC cells after insufficient RFA, and may be used to prevent the progression of HCC after RFA.

Low-frequency and low-intensity ultrasound-mediated microvessel disruption enhance the effects of radiofrequency ablation on prostate cancer xenografts in nude mice

The aim of the present study was to examine the impact of low-frequency, low-intensity ultrasound (US)-stimulated microbubbles (USMB) on radiofrequency ablation (RFA) in the treatment of nude mice with human prostate cancer xenografts. The tumor‑bearing nude mice were divided into three groups: The USMB+RFA group was treated with USMB immediately followed by RFA, the RFA group was treated with RFA alone, and the control group remained untreated. The animals underwent enhanced US to calculate the tumor volumes, ablation volumes and ablation rates. Subsequently, the tumors were excised for hematoxylin and eosin staining, to identify necrosis in the tumors following the treatments, and immunohistochemical staining, to analyze the apoptotic index (AI), proliferative index (PI) and microvessel density (MVD) at 1, 4 and 7 days post-treatment. Each group contained five mice at each time‑point. Necrosis was apparent in the center of the tumors in the treatment groups. Ablation lesion volumes of the USMB+RFA group were larger than those in the RFA group at 1 and 4 days post‑treatment (P=0.002 and P=0.022, respectively), and the ablation rates of the USMB+RFA group were significantly higher, compared with the RFA group at the three time‑points (all P<0.001). There were fewer apoptotic cells and more proliferative cells in the RFA group, compared with the control group 1,4 and 7 days post‑treatment (all P<0.05). The AI of the USMB+RFA group was higher than that of the control group and lower than that of the RFA group 1 day post-treatment (P=0.034 and P=0.016, respectively). The PI of the USMB+RFA group was lower than that of the control group and higher than that of the RFA group 4 and 7 days post-treatment (all P<0.05). No significant differences were observed in MVD among the three groups throughout the experiment. In conclusion, exposure to USMB prior to RFA produced larger volumes of ablation, compared with treatment with RFA alone, and increased AI and reduced PI in the residual carcinoma cells induced by RFA.

Maintenance of Clonogenic KIT(+) Human Colon Tumor Cells Requires Secretion of Stem Cell Factor by Differentiated Tumor Cells

BACKGROUND & AIMS

Colon tumors contain a fraction of undifferentiated stem cell-like cancer cells with high tumorigenic potential. Little is known about the signals that maintain these stem-like cells. We investigated whether differentiated tumor cells provide support.

METHODS

We established undifferentiated colonosphere cultures from human colon tumors and used them to generate stably differentiated cell lines. Antibody arrays were used to identify secreted factors. Expression of genes involved in stemness, differentiation, and the epithelial to mesenchymal transition was measured using reverse transcription quantitative polymerase chain reaction. Expression of KIT in human tumors was analyzed with gene expression arrays and by immunohistochemistry. Colonospheres were injected into the livers of CBy.Cg-Foxn1nu/J mice. After liver tumors had formed, hypoxia was induced by vascular clamping.

RESULTS

Differentiated cells from various tumors, or medium conditioned by them, increased the clonogenic capacity of colonospheres. Stem cell factor (SCF) was secreted by differentiated tumor cells and supported the clonogenic capacity of KIT(+) colonosphere cells. Differentiated tumor cells induced the epithelial to mesenchymal transition in colonosperes; this was prevented by inhibition of KIT or SCF. SCF prevented loss of clonogenic potential under differentiation-inducing conditions. Suppression of SCF or KIT signaling greatly reduced the expression of genes that regulate stemness and the epithelial to mesenchymal transition and inhibited clonogenicity and tumor initiation. Bioinformatic and immunohistochemical analyses revealed a correlation between expression of KIT- and hypoxia-related genes in colon tumors, which was highest in relapse-prone mesenchymal-type tumors. Hypoxia induced expression of KIT in cultured cells and in human colon tumor xenografts and this contributed to the clonogenic capacity of the tumor cells.

CONCLUSIONS

Paracrine signaling from SCF to KIT, between differentiated tumor cells and undifferentiated stem-like tumor cells, helps maintain the stem-like features of tumor cells, predominantly under conditions of hypoxia.

Systemic siRNA Nanoparticle-Based Drugs Combined with Radiofrequency Ablation for Cancer Therapy

PURPOSE

Radiofrequency thermal ablation (RFA) of hepatic and renal tumors can be accompanied by non-desired tumorigenesis in residual, untreated tumor. Here, we studied the use of micelle-encapsulated siRNA to suppress IL-6-mediated local and systemic secondary effects of RFA.

METHODS

We compared standardized hepatic or renal RFA (laparotomy, 1 cm active tip at 70 ± 2 °C for 5 min) and sham procedures without and with administration of 150 nm micelle-like nanoparticle (MNP) anti-IL6 siRNA (DOPE-PEI conjugates, single IP dose 15 min post-RFA, C57Bl mouse:3.5 ug/100ml, Fisher 344 rat: 20 ug/200 ul), RFA/scrambled siRNA, and RFA/empty MNPs. Outcome measures included: local periablational cellular infiltration (α-SMA+ stellate cells), regional hepatocyte proliferation, serum/tissue IL-6 and VEGF levels at 6-72 hr, and distant tumor growth, tumor proliferation (Ki-67) and microvascular density (MVD, CD34) in subcutaneous R3230 and MATBIII breast adenocarcinoma models at 7 days.

RESULTS

For liver RFA, adjuvant MNP anti-IL6 siRNA reduced RFA-induced increases in tissue IL-6 levels, α-SMA+ stellate cell infiltration, and regional hepatocyte proliferation to baseline (p < 0.04, all comparisons). Moreover, adjuvant MNP anti-IL6- siRNA suppressed increased distant tumor growth and Ki-67 observed in R3230 and MATBIII tumors post hepatic RFA (p<0.01). Anti-IL6 siRNA also reduced RFA-induced elevation in VEGF and tumor MVD (p < 0.01). Likewise, renal RFA-induced increases in serum IL-6 levels and distant R3230 tumor growth was suppressed with anti-IL6 siRNA (p < 0.01).

CONCLUSIONS

Adjuvant nanoparticle-encapsulated siRNA against IL-6 can be used to modulate local and regional effects of hepatic RFA to block potential unwanted pro-oncogenic effects of hepatic or renal RFA on distant tumor.

Preclinical Study of Locoregional Therapy of Hepatocellular Carcinoma by Bioelectric Ablation with Microsecond Pulsed Electric Fields (μsPEFs)

Unresectable hepatocellular carcinoma (HCC) needs locoregional ablation as a curative or downstage therapy. Microsecond Pulsed Electric Fields (μsPEFs) is an option. A xenograft tumor model was set up on 48 nude mice by injecting human hepatocellular carcinoma Hep3B cells subcutaneously. The tumor-bearing mice were randomly divided into 3 groups: μsPEFs treated, sham and control group. μsPEFs group was treated by μsPEFs twice in 5 days. Tumor volume, survival, pathology, mitochondria function and cytokines were followed up. μsPEFs was also conducted on 3 swine to determine impact on organ functions. The tumors treated by μsPEFs were completely eradicated while tumors in control and sham groups grew up to 2 cm(3) in 3 weeks. The μsPEFs-treated group indicated mitochondrial damage and tumor necrosis as shown in JC-1 test, flow cytometry, H&E staining and TEM. μsPEFs activates CD56+ and CD68+ cells and inhibits tumor proliferating cell nuclear antigen. μsPEFs inhibits HCC growth in the nude mice by causing mitochondria damage, tumor necrosis and non-specific inflammation. μsPEFs treats porcine livers without damaging vital organs. μsPEFs is a feasible minimally invasive locoregional ablation option.

Correlation between vascular endothelial growth factor levels and prognosis of hepatocellular carcinoma patients receiving radiofrequency ablation

This study is aimed to investigate the effect of serum vascular endothelial growth factor (VEGF) levels on prognosis of hepatocellular carcinoma (HCC) patients receiving radiofrequency ablation (RFA). The 110 HCC patients who received computed tomography (CT) guided RFA were enrolled in this study. The levels of serum VEGF were determined before and after RFA by enzyme-linked immunosorbent assay (ELISA). According to the ELISA results, the patients were divided into the negative group and the positive group. The patient's progression-free survival time was determined. It was demonstrated that the serum VEGF had no significant correlation with ages, sex and tumour size. There were no significant peripheral blood supplies around tumour necrosis. The results showed that higher levels of serum VEGF had a worse prognosis when compared to the patients with lower levels of serum VEGF. The difference between the area under the receiver operating characteristic curve and those when area under curves equalled 0.5 was statistically significant (P < 0.05). The serum VEGF level in liver cancer patients can be used as a prognostic indicator for evaluating the efficacy of RFA treatments.

Radiofrequency ablation-induced upregulation of hypoxia-inducible factor-1α can be suppressed with adjuvant bortezomib or liposomal chemotherapy

PURPOSE

To characterize upregulation of hypoxia-inducible factor (HIF)-1α after radiofrequency (RF) ablation and the influence of an adjuvant HIF-1α inhibitor (bortezomib) and nanodrugs on modulating RF ablation-upregulated hypoxic pathways.

MATERIALS AND METHODS

Fisher 344 rats (n = 68) were used. First, RF ablation-induced periablational HIF-1α expression was evaluated in normal liver or subcutaneous R3230 tumors (14-16 mm). Next, the effect of varying RF ablation thermal dose (varying tip temperature 50°C-90°C for 2-20 minutes) on HIF-1α expression was studied in R3230 tumors. Third, RF ablation was performed in R3230 tumors without or with an adjuvant HIF-1α inhibitor, bortezomib (single intraperitoneal dose 0.1 mg/kg). Finally, the combination RF ablation and intravenous liposomal chemotherapeutics with known increases in periablational cellular cytotoxicity (doxorubicin, paclitaxel, and quercetin) was assessed for effect on periablational HIF-1α. Outcome measures included immunohistochemistry of HIF-1α and heat shock protein 70 (marker of nonlethal thermal injury).

RESULTS

RF ablation increased periablational HIF-1α in both normal liver and R3230 tumor, peaking at 24-72 hours. Tumor RF ablation had similar HIF-1α rim thickness but significantly greater percent cell positivity compared with hepatic RF ablation (P < .001). HIF-1α after ablation was the same regardless of thermal dose. Bortezomib suppressed HIF-1α (rim thickness, 68.7 µm ± 21.5 vs 210.3 µm ± 85.1 for RF ablation alone; P < .02) and increased ablation size (11.0 mm ± 1.5 vs 7.7 mm ± 0.6 for RF ablation alone; P < .002). Finally, all three nanodrugs suppressed RF ablation-induced HIF-1α (ie, rim thickness and cell positivity; P < .02 for all comparisons), with liposomal doxorubicin suppressing HIF-1α the most (P < .03).

CONCLUSIONS

RF ablation upregulates HIF-1α in normal liver and tumor in a temperature-independent manner. This progrowth, hypoxia pathway can be successfully suppressed with an adjuvant HIF-1α-specific inhibitor, bortezomib, or non-HIF-1α-specific liposomal chemotherapy.

Nanodrug-enhanced radiofrequency tumor ablation: effect of micellar or liposomal carrier on drug delivery and treatment efficacy

PURPOSE

To determine the effect of different drug-loaded nanocarriers (micelles and liposomes) on delivery and treatment efficacy for radiofrequency ablation (RFA) combined with nanodrugs.

MATERIALS/METHODS

Fischer 344 rats were used (n = 196). First, single subcutaneous R3230 tumors or normal liver underwent RFA followed by immediate administration of i.v. fluorescent beads (20, 100, and 500 nm), with fluorescent intensity measured at 4-24 hr. Next, to study carrier type on drug efficiency, RFA was combined with micellar (20 nm) or liposomal (100 nm) preparations of doxorubicin (Dox; targeting HIF-1α) or quercetin (Qu; targeting HSP70). Animals received RFA alone, RFA with Lipo-Dox or Mic-Dox (1 mg i.v., 15 min post-RFA), and RFA with Lipo-Qu or Mic-Qu given 24 hr pre- or 15 min post-RFA (0.3 mg i.v.). Tumor coagulation and HIF-1α or HSP70 expression were assessed 24 hr post-RFA. Third, the effect of RFA combined with i.v. Lipo-Dox, Mic-Dox, Lipo-Qu, or Mic-Qu (15 min post-RFA) compared to RFA alone on tumor growth and animal endpoint survival was evaluated. Finally, drug uptake was compared between RFA/Lipo-Dox and RFA/Mic-Dox at 4-72 hr.

RESULTS

Smaller 20 nm beads had greater deposition and deeper tissue penetration in both tumor (100 nm/500 nm) and liver (100 nm) (p<0.05). Mic-Dox and Mic-Qu suppressed periablational HIF-1α or HSP70 rim thickness more than liposomal preparations (p<0.05). RFA/Mic-Dox had greater early (4 hr) intratumoral doxorubicin, but RFA/Lipo-Dox had progressively higher intratumoral doxorubicin at 24-72 hr post-RFA (p<0.04). No difference in tumor growth and survival was seen between RFA/Lipo-Qu and RFA/Mic-Qu. Yet, RFA/Lipo-Dox led to greater animal endpoint survival compared to RFA/Mic-Dox (p<0.03).

CONCLUSION

With RF ablation, smaller particle micelles have superior penetration and more effective local molecular modulation. However, larger long-circulating liposomal carriers can result in greater intratumoral drug accumulation over time and reduced tumor growth. Accordingly, different carriers provide specific advantages, which should be considered when formulating optimal combination therapies.

Value of radiofrequency ablation in the treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a malignant disease that substantially affects public health worldwide. It is especially prevalent in east Asia and sub-Saharan Africa, where the main etiology is the endemic status of chronic hepatitis B. Effective treatments with curative intent for early HCC include liver transplantation, liver resection (LR), and radiofrequency ablation (RFA). RFA has become the most widely used local thermal ablation method in recent years because of its technical ease, safety, satisfactory local tumor control, and minimally invasive nature. This technique has also emerged as an important treatment strategy for HCC in recent years. RFA, liver transplantation, and hepatectomy can be complementary to one another in the treatment of HCC, and the outcome benefits have been demonstrated by numerous clinical studies. As a pretransplantation bridge therapy, RFA extends the average waiting time without increasing the risk of dropout or death. In contrast to LR, RFA causes almost no intra-abdominal adhesion, thus producing favorable conditions for subsequent liver transplantation. Many studies have demonstrated mutual interactions between RFA and hepatectomy, effectively expanding the operative indications for patients with HCC and enhancing the efficacy of these approaches. However, treated tumor tissue remains within the body after RFA, and residual tumors or satellite nodules can limit the effectiveness of this treatment. Therefore, future research should focus on this issue.

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.

TRAIL-secreting mesenchymal stem cells promote apoptosis in heat-shock-treated liver cancer cells and inhibit tumor growth in nude mice

Liver cancer is one of the top six leading causes of cancer-related death. Radiofrequency ablation (RFA) is an important means of treating liver cancer. Residual cancer after RFA is the most frequent cause of recurrence in cases of liver cancer. The main difference between residual cancer cells and ordinary liver cancer cells is that residual cancer cells experience heat shock. The secretable form of trimeric human tumor necrosis factor-related apoptosis-inducing ligand (stTRAIL) induces apoptosis in a variety of human cancers but not in normal tissues. It has shown potent cancer-selective killing activity and has drawn considerable attention as a possible cancer therapy. In the present work, the therapeutic potential of this stTRAIL-based gene therapy was evaluated in hepatocellular carcinoma subjected to RFA. Rat bone marrow mesenchymal stem cells (BM-MSCs) were isolated and transduced with a lentiviral vector encoding stTRAIL (stTRAIL-MSCs, T-MSCs). Cells treated with heat treatment at 43 °C for 45 min served as simulated residual cancer cells. After treatment with T-MSCs, apoptosis in heat-shock-treated liver cancer cells increased significantly, and caspase-3 was upregulated. When T-MSCs were subcutaneously injected into nude mice, they localized to the tumors and inhibited tumor growth, significantly increasing survival. Collectively, the results of the present study indicate that BM-MSC can provide a steady source of stTRAIL and may be suitable for use in the prevention of the recurrence of hepatocellular carcinoma after RFA with secretable trimeric TRAIL.

[Change of ERCC1 expression of residual VX2 squamous carcinoma cells in rabbit lung after radiofrequency ablation]

背景与目的

残存肿瘤是影响射频消融（radiofrequency ablation, RFA）治疗肺恶性肿瘤效果的重要因素，联合铂类药物化疗是减少残存肿瘤的重要手段之一。核苷酸切除修复交叉互补基因1（excision repair cross-complementation group 1, ERCC1）的表达水平是影响铂类药物化疗效果的重要因素之一。RFA治疗后残存肿瘤会发生一些生物学特性变化，但有关ERCC1表达变化的研究尚无报道。本研究旨在探讨RFA治疗后兔肺内残存VX2鳞癌细胞ERCC1表达水平的变化。

方法

应用组织块悬液注射法建立兔VX2鳞癌肺内移植瘤模型。58只荷瘤新西兰白兔随机分为对照组（n=10）和RFA组（n=48）。在RFA治疗时，通过控制电极展开范围、输出功率、治疗时间的方法，造成肿瘤残存。应用免疫组织化学方法检测残存肿瘤细胞在不同时间点ERCC1表达的阳性率。

结果

RFA组残存肿瘤组织ERCC1表达阳性率在1 d-5 d呈一过性升高（53.7%±1.6% & 32.9%±2.5%），5 d后恢复至对照组水平。

结论

因在RFA治疗后1 d-5 d内残存肿瘤细胞ERCC1表达增高，在此期间给予铂类药物化疗可能效果不佳。

Molecular changes in bone marrow, tumor and serum after conductive ablation of murine 4T1 breast carcinoma

Thermal ablation of solid tumors using conductive interstitial thermal therapy (CITT) produces coagulative necrosis in the center of ablation. Local changes in homeostasis for surviving tumor and systemic changes in circulation and distant organs must be understood and monitored in order to prevent tumor re-growth and metastasis. The purpose of this study was to use a mouse carcinoma model to evaluate molecular changes in the bone marrow and surviving tumor after CITT treatment by quantification of transcripts associated with cancer progression and hyperthermia, serum cytokines, stress proteins and the marrow/tumor cross-talk regulator stromal-derived factor 1. Analysis of 27 genes and 22 proteins with quantitative PCR, ELISA, immunoblotting and multiplex antibody assays revealed that the gene and protein expression in tissue and serum was significantly different between ablated and control mice. The transcripts of four genes (Cxcl12, Sele, Fgf2, Lifr) were significantly higher in the bone marrow of treated mice. Tumors surviving ablation showed significantly lower levels of the Lifr and Sele transcripts. Similarly, the majority of transcripts measured in tumors decreased with treatment. Surviving tumors also contained lower levels of SDF-1α and HIF-1α proteins whereas HSP27 and HSP70 were higher. Of 16 serum chemokines, IFNγ and GM-CSF levels were lower with treatment. These results indicate that CITT ablation causes molecular changes which may slow cancer cell proliferation. However, inhibition of HSP27 may be necessary to control aggressiveness of surviving cancer stem cells. The changes in bone marrow are suggestive of possible increased recruitment of circulatory cancer cells. Therefore, the possibility of heightened bone metastasis after thermal ablation needs to be further investigated and inhibition strategies developed, if warranted.

Insufficient radiofrequency ablation promotes epithelial-mesenchymal transition of hepatocellular carcinoma cells through Akt and ERK signaling pathways

Background

Residual tumor progression after insufficient radiofrequency ablation (RFA) has been recently reported. However, whether epithelial-mesenchymal transition (EMT), which is a key process that drives cancer metastasis, is involved in the tumor progression after insufficient RFA is not well understood.

Methods

Human hepatocellular carcinoma (HCC) cell lines SMMC7721 and Huh7 were used. Insufficient RFA was simulated using a water bath (47°C 5 min, 10 min, 15 min, 20 min and 25 min gradually). MTT assay was used to evaluate the proliferation of HCC cells in vitro. Migration and invasion of HCC cells were determined by transwell assay. The molecular changes in HCC cells after insufficient RFA were evaluated by western blot. LY294002 and PD98059 were used to treat HCC cells. An ectopic nude mice model and a tail vein metastatic assay were used to evaluate the growth and metastatic potential of SMMC7721 cells in vivo after insufficient RFA.

Results

SMMC7721 and Huh7 cells after insufficient RFA (named as SMMC7721-H and Huh7-H respectively) exhibited enhanced proliferation, migration and invasion (6.4% and 23.6%, 33.2% and 66.1%, and 44.1% and 57.4% increase respectively) in vitro. Molecular changes of EMT were observed in SMMC7721-H and Huh7-H cells. LY294002 and PD98059 inhibited the EMT of SMMC7721-H and Huh7-H cells. SMMC7721-H cells also exhibited larger tumor size (1440.8 ± 250.3 mm³ versus 1048.56 ± 227.6 mm³) and more lung metastasis (97.4% increase) than SMMC7721 cells in vivo. Higher expression of PCNA, N-cadherin and MMP-2 and MMP-9, was also observed in SMMC7721-H tumors.

Conclusions

Insufficient RFA could directly promote the invasiveness and metastasis of HCC cells. Insufficient RFA may promote the EMT of HCC cells through Akt and ERK signaling pathways.

After insufficient radiofrequency ablation, tumor-associated endothelial cells exhibit enhanced angiogenesis and promote invasiveness of residual hepatocellular carcinoma

Background

The mechanism regarding rapid progression of residual hepatocellular carcinoma (HCC) after insufficient radiofrequency ablation (RFA) has been preliminarily discussed. However, most studies have mainly focused on RFA-induced changes in the tumor cells. The present study was designed to determine whether tumor-associated endothelial cells (TAECs) could contribute to the invasiveness of HCC after insufficient RFA.

Methods

TAECs were isolated from fresh HCC tissue and characterized. Morphological changes were observed in TAECs after heat treatment for 10 min. TAEC proliferation, migration and tube formation after heat treatment for 10 min at 37°C (control group), and 42 and 47°C (insufficient RFA groups) were examined. The differences in TAECs interactions with HepG2-GFP or HCCLM3-GFP cells among the two insufficient RFA groups and control group were evaluated. The expression of E-selectin, ICAM-1 and VCAM-1 in TAECs was measured. The effects of TAECs on the invasiveness of HepG2-GFP or HCCLM3-GFP cells after insufficient RFA were analyzed. The IL-6, IL-8, MCP-1 and GRO-α concentrations in conditioned medium from TAECs were measured after insufficient RFA. The associated signaling pathways of Akt, ERK1/2, STAT3 and NF-κB were analyzed in TAECs after insufficient RFA.

Results

TAECs expressed the EC-specific markers and took up complexes of Dil-Ac-LDL. Relative to the control group, the proliferation of TAECs was significantly inhibited and their migration and tube formation were significantly enhanced in the insufficient RFA groups. Significantly more HepG2-GFP or HCCLM3-GFP cells adhered to TACEs in these groups than in the control group (all P<0.001), via up-regulated expression of E-selectin, ICAM-1 and VCAM-1. TAECs promoted the invasiveness of HepG2-GFP or HCCLM3-GFP cells after insufficient RFA via the up-regulation of IL-6, IL-8, MCP-1 and GRO-α in conditioned medium (all P<0.05). Insufficient RFA enhanced the activities of Akt, ERK1/2 and NF-κB signaling pathways and inhibited STAT3 signaling pathways.

Conclusions

Insufficient RFA enhanced TAEC migration and tube formation, and this may play a key role in the rapid growth of residual HCC. Increased expression of metastasis-related molecules in TAECs after insufficient RFA may be a potential mechanism for the metastasis of residual HCC.

Conductive thermal ablation of 4T1 murine breast carcinoma reduces severe hypoxia in surviving tumour

PURPOSE

The purpose of this study was to quantify hypoxia changes in viable tumour volumes after thermal ablation of a murine breast carcinoma.

METHODS

Murine breast 4T1 tumours were grown in the rear leg of BALB/c mice to an average diameter of 10-12 mm. Tumours were treated with conductive interstitial thermal therapy (CITT) at a peak temperature of 80-90°C for 10 min. The animals were euthanised 72 h later, and the tumours were removed for immunohistochemical staining with pimonidazole - a marker of partial pressure of oxygen. The levels of pimonidazole staining intensity were used to quantify changes in hypoxia gradients in terms of strong, medium and weak positive pixel fractions.

RESULTS

The pimonidazole staining ratio of viable control tumour tissue to viable tissue in tumours that were ablated was 0.7 for weak staining, 2.7 for medium staining and 8.0 (p < 0.03) for strong pimonidazole staining.

CONCLUSION

This shift of pimonidazole staining toward lower intensity pixels in the remaining tumour indicates that tumour ablation with CITT may increase radiosensitivity of the remaining tumour tissue and presents a rationale for combination therapy.

Patterns of histological changes following hepatic electrolytic ablation in an ex-vivo perfused model

Electrolytic ablation (EA) destroys the liver by releasing toxic radicles and producing modifications in the local pH without increasing the tissue temperature. We assessed the histological changes produced by EA using an ex-vivo perfused model. Five porcine livers were harvested, preserved in ice and reperfused for six hours in an extracorporeal circuit using autologous normothermic blood. One hour after reperfusion EA was performed and liver biopsies collected at the end of the experiments. The main necrotic zone consisted of coagulative necrosis, sinusoidal dilatation and haemorrhage with an unusual morphological pattern. The coagulative necrosis and haemorrhage affected mainly the peripheral area of the lobule with relative sparing of the area surrounding the centrilobular vein. Contrasting with this sinusoidal dilatation appeared to be more prominent in the centrilobular area. EA produces patterns of tissue destruction that have not been observed with the more commonly used thermal techniques. Further studies should obtain more information about the influence of adjacent biliary and vascular structures so that appropriate clinical trials can be designed.

Does Radiofrequency Ablation Add to Chemotherapy for Unresectable Liver Metastases?

In patients with unresectable colorectal liver metastases (CRLM), radiofrequency ablation (RFA) might be a good alternative, whenever possible. In contrast to systemic therapy, the aim of RFA is to achieve complete local tumor control in an attempt to provide long-term survival. In this article we discuss the available evidence regarding the treatment of patients with unresectable CRLM, focusing on RFA in conjunction with modern systemic therapies. We observed that the available evidence in the existing literature is limited, and often consists of level 2 and 3 evidence, thereby hampering any firm conclusions. Nonetheless, RFA seems superior to chemotherapy alone in patients with liver-only disease amenable for RFA. However, the combination of RFA and chemotherapy has been demonstrated to be feasible and safe, lending support to the concept of RFA followed by chemotherapy, in order to reduce local recurrence rates and prolong survival.

Incomplete thermal ablation stimulates proliferation of residual renal carcinoma cells in a translational murine model

What's known on the subject? and What does the study add? Thermal ablation influences the local tissue microenvironment. Several studies have reported that residual tumour cells may exhibit a more aggressive phenotype. This study shows that incomplete CA and RFA cause an increased proliferation and decreased apptosis of residual renal tumour cells. This may be caused by stimulatory factors such as hypoxia, HSPs and inflammatory cells.

OBJECTIVE

To compare the effect of incomplete thermal ablation vs partial nephrectomy (PN) on growth stimulation and cellular survival in renal tumours.

MATERIALS AND METHODS

Renca renal tumours were transplanted under the renal capsule of mice (four to six mice/group) after which incomplete radiofrequency ablation (RFA), cryoablation (CA) or PN was performed. At several time points after treatment, presence of cell proliferation, apoptosis, hypoxic areas, inflammatory factors and the heat-shock proteins (HSPs) 70 and 90 were evaluated using immunohistochemistry.

RESULTS

At 2 h after thermal ablation residual tumour cells showed increased proliferation. This hyperproliferation was significantly stronger after RFA than CA (P < 0.05) and not present after PN. Residual cells showed increased apoptosis after 2 h and decreased apoptosis from 2 days after thermal ablation. Apoptotic cells were significantly less evident at 3 days after RFA (P < 0.001). Hypoxic areas and HSPs were increasingly present from 2 h up to 7 days after thermal ablation (P < 0.001). Inflammatory cells infiltrated mainly the necrotic areas after thermal ablation, and their abundance peaked at 1 week after ablation (P < 0.05). The increased cell growth was preceded by hypoxia and presence of HSPs.

CONCLUSIONS

CA and RFA result in an increased proliferation and decreased apoptosis of residual renal tumour cells. This hyperproliferation may be caused by stimulatory factors, e.g. hypoxia, HSPs and inflammatory cells, and could facilitate recurrences of renal tumours after thermal ablation. This study highlights the importance of achieving complete tumour destruction.

Insufficient radiofrequency ablation promotes angiogenesis of residual hepatocellular carcinoma via HIF-1α/VEGFA

Background

The mechanism of rapid growth of the residual tumor after radiofrequency (RF) ablation is poorly understood. In this study, we investigated the effect of hyperthermia on HepG2 cells and generated a subline with enhanced viability and dys-regulated angiogenesis in vivo, which was used as a model to further determine the molecular mechanism of the rapid growth of residual HCC after RF ablation.

Methodology/Principal Findings

Heat treatment was used to establish sublines of HepG2 cells. A subline (HepG2 k) with a relatively higher viability and significant heat tolerance was selected. The cellular protein levels of VEGFA, HIF-1α and p-Akt, VEGFA mRNA and secreted VEGFA were measured, and all of these were up-regulated in this subline compared to parental HepG2 cells. HIF-1α inhibitor YC-1 and VEGFA siRNA inhibited the high viability of the subline. The conditioned media from the subline exerted stronger pro-angiogenic effects. Bevacizumab, VEGFA siRNA and YC-1 inhibited proangiogenic effects of the conditioned media of HepG2 k cells and abolished the difference between parental HepG2 cells and HepG2 k cells. For in vivo studies, a nude mouse model was used, and the efficacy of bavacizumab was determined. HepG2 k tumor had stronger pro-angiogenic effects than parental HepG2 tumor. Bevacizumab could inhibit the tumor growth and angiogenesis, and also eliminate the difference in tumor growth and angiogenesis between parental HepG2 tumor and HepG2 k tumor in vivo.

Conclusions/Significance

The angiogenesis induced by HIF1α/VEGFA produced by altered cells after hyperthermia treatment may play an important role in the rapid growth of residual HCC after RF ablation. Bevacizumab may be a good candidate drug for preventing and treating the process.

Low-dose steroid pretreatment ameliorates the transient impairment of liver regeneration

AIM

To determine if liver regeneration (LR) could be disturbed following radiofrequency (RF) ablation and whether modification of LR by steroid administration occurs.

METHODS

Sham operation, partial hepatectomy (PH), and partial hepatectomy with radiofrequency ablation (PHA) were performed on adult Fisher 344 rats. We investigated the recovery of liver volume, DNA synthetic activities, serum cytokine/chemokine levels and signal transducers and activators of transcription 3 DNA-binding activities in the nucleus after the operations. Additionally, the effects of steroid (dexamethasone) pretreatment in the PH group (S-PH) and the PHA group (S-PHA) were compared.

RESULTS

The LR after PHA was impaired, with high serum cytokine/chemokine induction compared to PH, although the ratio of the residual liver weight to body weight was not significantly different. Steroid pretreatment disturbed LR in the S-PH group. On the other hand, low-dose steroid pretreatment improved LR and suppressed tumor necrosis factor (TNF)-α elevation in the S-PHA group, with recovery of STAT3 DNA-binding activity. On the other hand, low-dose steroid pretreatment improved LR and suppressed TNF-α elevation in the S-PHA group, with recovery of STAT3 DNA-binding activity.

CONCLUSION

LR is disturbed after RF ablation, with high serum cytokine/chemokine induction. Low-dose steroid administration can improve LR after RF ablation with TNF-α suppression.

Effects of tirapazamine on experimental colorectal liver metastases after radiofrequency ablation1

Background

Radiofrequency ablation (RFA) is a common procedure for the management of colorectal liver metastases. RFA-generated lesions are surrounded by a rim of hypoxia that is associated with aggressive outgrowth of intrahepatic micrometastases. Hypoxia-activated prodrugs such as tirapazamine are designed selectively to induce apoptosis in tumour cells under hypoxic conditions. Therefore, it was hypothesized that tirapazamine may have therapeutic value in limiting hypoxia-associated tumour outgrowth following RFA.

Methods

Murine C26 and MC38 colorectal cancer cells were grown under hypoxia and normal oxygenation in vitro, and treated with different concentrations of tirapazamine. Apoptosis and cell cycle distribution were assessed by western blot and fluorescence-activated cell sorting analysis. Proliferative capacity was tested by means of colony-formation assays. Mice harbouring microscopic colorectal liver metastases were treated with RFA, followed by a single injection of tirapazamine (60 mg/kg) or saline. Tumour load was assessed morphometrically 7 days later.

Results

Tirapazamine induced apoptosis of colorectal tumour cells under hypoxia in vitro. Under normal oxygenation, tirapazamine caused a G2 cell cycle arrest from which cells recovered partly. This reduced, but did not abolish, colony-forming capacity. A single dose of tirapazamine largely prevented accelerated outgrowth of hypoxic micrometastases following RFA. Tirapazamine administration was associated with minimal toxicity.

Conclusion

Tirapazamine induced apoptosis in colorectal cancer cells in a hypoxia-dependent manner and potently suppressed hypoxia-associated outgrowth of liver metastases with limited toxicity. This warrants further study to assess the potential value of tirapazamine, or other hypoxia-activated prodrugs, as adjuvant therapeutics following RFA treatment of colorectal liver metastases.

Proliferative activity in hepatocellular carcinoma is closely correlated with glucose metabolism but not angiogenesis

BACKGROUND & AIMS

This study investigated the relationship between tumor proliferative activity and the grade of tumor glucose metabolism or angiogenesis in hepatocellular carcinoma (HCC).

METHODS

The study was performed as a retrospective analysis of 63 patients with HCC who underwent fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) as a preoperative examination prior to liver resection. Tumor proliferative activity was evaluated by the Ki-67 labeling index (LI). The grade of tumor glucose metabolism was evaluated by measuring the protein expression level of glucose transporter (GLUT)-1, expression level of pyruvate kinase type M2 (PKM2) mRNA, and FDG uptake. The grade of tumor angiogenesis was evaluated by the protein expression level of vascular endothelial growth factor (VEGF) and tumor microvessel density.

RESULTS

All patients were divided into tertiles according to the Ki-67 LI: the low LI group (n = 21), the intermediate LI group (n = 21), and the high LI group (n = 21). The high LI group showed a tendency to have advanced tumor stage, and lower disease-free survival and overall survival rates than the low LI and the intermediate LI groups. The expression grade of GLUT-1, PKM2 mRNA, and FDG uptake gradually increased with the Ki-67 LI. On the other hand, the protein expression grade of VEGF and microvessel density was paradoxically decreased with the Ki-67 LI.

CONCLUSIONS

These data suggest that (1) the proliferative activity of a resected specimen predicted the prognosis in patients with HCC; (2) the proliferative activity was closely correlated with the glucose metabolism, but not with angiogenesis.

Radiofrequency ablation vs hepatic resection for solitary colorectal liver metastasis: A meta-analysis

AIM: To evaluate the comparative therapeutic efficacy of radiofrequency ablation (RFA) and hepatic resection (HR) for solitary colorectal liver metastases (CLM).

METHODS: A literature search was performed to identify comparative studies reporting outcomes for both RFA and HR for solitary CLM. Pooled odds ratios (OR) with 95% confidence intervals (95% CI) were calculated using either the fixed effects model or random effects model.

RESULTS: Seven nonrandomized controlled trials studies were included in this analysis. These studies included a total of 847 patients: 273 treated with RFA and 574 treated with HR. The 5 years overall survival rates in the HR group were significantly better than those in the RFA group (OR: 0.41, 95% CI: 0.22-0.90, P = 0.008). RFA had a higher rate of local intrahepatic recurrence compared to HR (OR: 4.89, 95% CI: 1.73-13.87, P = 0.003). No differences were found between the two groups with respect to postoperative morbidity and mortality.

CONCLUSION: HR was superior to RFA in the treatment of patients with solitary CLM. However, the findings have to be carefully interpreted due to the lower level of evidence.

A role for CD95 signaling in ischemia/reperfusion-induced invasion and outgrowth of colorectal micrometastases in mouse liver

BACKGROUND

Ischemia/reperfusion (I/R) injury in the liver is associated with accelerated outgrowth of micrometastases. The aim of the study was to test the role of CD95 signaling in accelerated outgrowth of colorectal liver metastases following I/R.

METHODS

Mice underwent vascular clamping 5 days after induction of colorectal liver metastases. Invasion and outgrowth of micrometastases following I/R were analyzed by post-mortem confocal microscopy (36 hr post-I/R) and by morphometric assessment of tumor load (5 days post-I/R), respectively. Tumor cell CD95 was suppressed by lentiviral RNA interference. The contribution of host CD95L was assessed by using gld-mice lacking functional CD95L.

RESULTS

CD95-knockdown in tumor cells strongly reduced perinecrotic invasion (tumor diameter from ∼830 to ∼470 µm) and largely prevented outgrowth acceleration of perinecrotic liver metastases following I/R (from ∼8- to ∼4.5-fold). In gld-mice, the relative hepatic area with necrosis was markedly reduced. Perinecrotic tumor cell clusters still displayed an invasive phenotype (tumor diameter of ∼980 µm). However, I/R-induced acceleration of tumor outgrowth was reduced in gld-mice from ∼8- to ∼5-fold.

CONCLUSIONS

I/R induces invasion and accelerated outgrowth of preestablished metastases in a CD95-dependent manner. Activation of the CD95 system following I/R not only contributes to liver injury, but may also promote aggressive tumor recurrence.

Radiofrequency ablation of colorectal hepatic metastases

Radiofrequency ablation (RFA) may be performed intraoperatively, laparoscopically, or percutaneously. The percutaneous approach is associated with the least procedural risk and may be performed under local anesthesia. Percutaneous RFA should be considered a primary treatment option for patients with unresectable hepatic tumors or conditions that prohibit general anesthesia or abdominal surgery. Continually improving thermal ablation and imaging technologies are likely to further increase tumor ablation efficacy and expand its role in treatment of hepatic metastases.

Adjuvant radioimmunotherapy after radiofrequency ablation of colorectal liver metastases in an experimental model

PURPOSE

Radiofrequency ablation (RFA) has shown to improve survival in patients not eligible for surgical resection of colorectal liver metastases. However, recurrences after RFA are a major problem. Adjuvant radioimmunotherapy (RIT) after surgical resection of liver metastases has shown to improve survival. The aim of the present study was to test the hypothesis that adjuvant RIT might be an effective way to prevent recurrent liver metastases after RFA in an experimental model.

METHODS

Tumours in the liver were induced by intrahepatic injection of 300,000 CC531 cells in male Wag/Rij rats (n = 60). Ten days later, the intrahepatic tumours were treated with RFA. Adjuvant RIT ((177)Lu-labelled monoclonal antibody MG1 at 300 MBq/kg) was administered intravenously either at the day of RFA (day 10) or 7 days later. Control rats received no treatment. Primary endpoint was survival.

RESULTS

Administration of (177)Lu-MG1 resulted in a transient decrease in body weight, compared to no adjuvant treatment. However, no other signs of clinical discomfort were registered. Log rank test showed that the survival curves of the groups treated with RIT, either at day 10 or day 17, did not differ significantly from the survival curve of the rats that did not receive adjuvant treatment (P = 0.902).

CONCLUSION

This study shows that adjuvant RIT does not increase survival after RFA of colorectal liver metastases in rats.

CD95 is a key mediator of invasion and accelerated outgrowth of mouse colorectal liver metastases following radiofrequency ablation

BACKGROUND & AIMS

Recently, we have shown that micro-metastases, in the hypoxic transition zone surrounding lesions generated by radiofrequency ablation (RFA), display strongly accelerated outgrowth. CD95 is best known for its ability to induce apoptosis but can also promote tumorigenesis in apoptosis-resistant tumor cells. Therefore, we tested whether CD95 signaling plays a role in accelerated outgrowth of colorectal liver metastases following RFA.

METHODS

Hypoxia-induced invasion was assessed in three-dimensional EGFP-expressing C26 tumor cell cultures by confocal microscopy. CD95 localization was tested by immunofluorescence. Invasion and outgrowth of liver metastases following RFA were analyzed by post-mortem confocal microscopy and by morphometric assessment of tumor load. Neutralization of CD95L was performed by using antibody MFL4. CD95 was suppressed by lentiviral RNA interference. The role of host CD95L was assessed using gld mice.

RESULTS

Micro-metastases in the hypoxic transition zone following RFA displayed a highly invasive phenotype and increased expression of CD95 and CD95L. Hypoxia-induced tumor cell invasion in vitro increased the expression of CD95 and CD95L and induced translocation of CD95 to the invasive front. In vitro invasion, metastasis invasion, and accelerated tumor growth in the transition zone were strongly suppressed by neutralizing CD95L or by suppressing tumor cell CD95. In contrast, metastasis invasion and outgrowth were unaffected in gld mice.

CONCLUSIONS

Hypoxia causes autocrine activation of CD95 on colorectal tumor cells, thereby promoting local invasion and accelerated metastasis outgrowth in the hypoxic transition zone following RFA. Further pre-clinical work is needed to assess the role of CD95L neutralization, either alone or in combination with chemotherapy, in limiting aggressive recurrence of liver metastases following RFA.

Radiofrequency ablation of colorectal liver metastases induces an inflammatory response in distant hepatic metastases but not in local accelerated outgrowth

BACKGROUND

Recently, we have shown in a murine model that radiofrequency ablation (RFA) induces accelerated outgrowth of colorectal micrometastases in the transition zone (TZ) surrounding the ablated lesion. Conversely, RFA also induces an anti-tumor T-cell response that may limit tumor growth at distant sites. Here we have evaluated whether an altered density of inflammatory cells could be observed in the perinecrotic (TZ) metastases compared to hepatic metastases in the distant reference zone (RZ).

METHODS

RFA-treated tumor-bearing mice (n = 10) were sacrificed. The inflammatory cell density (neutrophils, macrophages, CD4(+) T-cells, and CD8(+) T-cells) of tumors in the TZ (TZ tumors) was compared to that in tumors in the RZ (RZ tumors). Sham-operated, tumor-bearing mice (n = 10) were analyzed simultaneously as controls (sham-treated tumors).

RESULTS

In RFA-treated, tumor-bearing mice RZ tumors contained a significantly higher density of neutrophils and CD4(+) T-cells, but not macrophages and CD8(+) T-cells compared to sham-treated tumors. Notably, TZ tumors had a significantly lower density of neutrophils, CD4(+) T-cells, and CD8(+) T-cells, but not macrophages, when compared to RZ tumors.

CONCLUSIONS

The accelerated perinecrotic tumor outgrowth following RFA is associated with a reduced density of neutrophils and T-cells compared to distant hepatic metastases. This may have implications for local tumor recurrence following RFA.