DNA-PKcs subunits in radiosensitization by hyperthermia on hepatocellular carcinoma hepG2 cell line

The miR-34a-5p-c-MYC-CHK1/CHK2 Axis Counteracts Cancer Stem Cell-Like Properties and Enhances Radiosensitivity in Hepatocellular Cancer Through Repression of the DNA Damage Response

Radiotherapy has become an increasingly widespread modality for treating hepatocellular cancer (HCC); however, the development of radioresistance significantly limits its effectiveness and invariably leads to tumor recurrence. Cancer stem cell (CSC) theory offers a potential explanation for tumor relapse and radioresistance, but the underlying mechanism remains unknown. Herein we investigate the role of miRNA in molecular regulation of stemness and radioresistance in HCC. Two HCC radiation-resistant cell lines (Huh7-RR and SMMC-7721-RR) were established by selecting the radioresistant subpopulation from HCC cells via clonogenic survival assays. MiRNA Sequencing was used to identify potential radiosensitivity involved miRNA in HCC-RR cells. Xenograft tumor mouse model was established for in vivo study. CSC properties were assessed using sphere formation assay and side population (SP) cells analysis. We found that miR-34a-5p was significantly downregulated in HCC-RR cells. Overexpression of miR-34a-5p counteracts CSC properties and enhances radiosensitivity in HCC. Mechanistic investigation revealed that c-MYC is the direct target of miR-34a-5p. Overexpression of miR-34a-5p reversed c-MYC-induced radioresistance. Moreover, we found that the specific molecular mechanism was that c-MYC activated CHK1 and CHK2, which are two key DNA damage checkpoint kinases, and facilitated the DNA damage response to radiation. Repression of the miR-34a-5p-cMYC-CHK1/CHK2 axis contributes to the acquisition of radioresistance in HCC cells. In summary, the miR-34a-5p-c-MYC-CHK1/CHK2 axis counteracts cancer stem cell-like properties and enhances radiosensitivity in hepatocellular cancer through repression of the DNA damage response.

To explore the curative effect of CT-guided Iodine-125 radioactive seed implantation in the treatment of stage Ⅳprimary hepatocellular carcinoma

Objectives

To explore the clinical efficacy and survival of CT-guided Iodine-125 radioactive seed implantation in the treatment of stage Ⅳ primary hepatocellular carcinoma.

Methods

A retrospective study of 62 patients with primary hepatocellular carcinoma in our hospital from January 2017 to December 2018 [60 males, 2 females, age (52.76 ​± ​10.82) years old], All patients were implanted with Iodine-125 radioactive seeds under CT guidance, followed up regularly after operation to observe the clinical efficacy, including comparison of changes in cancer size before and after treatment, tumor marker AFP, and improvement in complications such as abdominal pain and ascites. Follow-up 3–36 months to assess patient survival.

Results

Among the 62 patients, 3 months after Iodine-125 radioactive seed implantation, 5 cases (8.1%) had complete remission of cancer, 33 cases (53.2%) had partial remission, 12 cases (19.4%) had stable lesions, and 12 cases (19.4%) had disease progression. The effective rate was 61.3%. The tumor volume (31.44 ​± ​14.51cm3) was significantly smaller than before (50.96 ​± ​30.13cm3) (t ​= ​5.303, p ​< ​0.05). The tumor marker AFP (69.28 ​± ​50.99) ug/L of 3 months after implantation was significantly lower than that before treatment (90.63 ​± ​68.58) ug/L (t ​= ​3.702, P ​< ​0.05). The average survival time of Iodine-125 seed implantation for stageⅣhepatocellular carcinoma is 11.47 ​± ​0.85 months, and the median survival time is 9 months. The survival time of the group with better pathological differentiation (gradeⅠ+Ⅱ) was significantly better than that of the group with poor differentiation (grade Ⅲ+Ⅳ) (x2 ​= ​6.869 p ​< ​0.05). Among the 38 patients with different degrees of abdominal pain, 22 patients improved better than before; 15 of 28 patients with different degrees of ascites were better than before. All patients had no serious complications related to treatment.

Conclusions

Iodine-125 radioactive seed implantation therapy can safely and effectively treat hepatocellular carcinoma, and relieve the clinical symptoms of abdominal pain and ascites.

Predictive factors for survival following stereotactic body radiotherapy for hepatocellular carcinoma with portal vein tumour thrombosis and construction of a nomogram

Background

We evaluated the treatment response and predictive factors for overall survival (OS) in patients with hepatocellular carcinoma (HCC) and portal vein tumour thrombosis (PVTT), who underwent stereotactic body radiotherapy (SBRT). Additionally, we developed and validated a personalised prediction model for patient survival.

Methods

Clinical information was retrospectively collected for 80 patients with HCC and PVTT, who were treated with SBRT at the Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital) between December 2015 and June 2019. A multivariate Cox proportional hazard regression model was used to identify the independent predictive factors for survival. Clinical factors were subsequently presented in a nomogram. The area under the receiver operating characteristic curve (AUC) and decision curve analysis (DCA) were used to evaluate the accuracy of the model and the net clinical benefit.

Results

All patients completed the planned radiotherapy treatment, and the median follow-up duration was 10 months (range, 1–35.3 months). The median survival duration was 11.5 months, with 3-, 6-, and 12-month survival rates of 92.5, 74.5, and 47.5%, respectively. The multivariable Cox regression model indicated that the following were significant independent predictors of OS: clinical T stage (p = 0.001, hazard ratio [HR] = 3.085, 95% confidence interval [CI]: 1.514–6.286), cirrhosis (p = 0.014, HR = 2.988, 95% CI: 1.246–7.168), age (p = 0.005, HR = 1.043, 95% CI: 1.013–1.075), alpha-fetoprotein level (p = 0.022, HR = 1.000, 95% CI: 1.000–1.000), and haemoglobin level (p = 0.008, HR = 0.979, 95% CI: 0.963–0.994). A nomogram based on five independent risk factors and DCA demonstrated a favourable predictive accuracy of patient survival (AUC = 0.74, 95% CI: 0.63–0.85) and the clinical usefulness of the model.

Conclusions

SBRT is an effective treatment for patients with HCC with PVTT. Notably, clinical T stage, presence of cirrhosis, age, alpha-fetoprotein levels, and haemoglobin levels are independent prognostic factors for survival. The presented nomogram can be used to predict the survival of patients with HCC and PVTT, who underwent SBRT.

lncRNA MIR22HG-Derived miR-22-5p Enhances the Radiosensitivity of Hepatocellular Carcinoma by Increasing Histone Acetylation Through the Inhibition of HDAC2 Activity

Background

With the development of radiotherapy technology, radiotherapy has been increasingly used to treat primary hepatocellular carcinoma (HCC). However, due to radioresistance and the intolerance of the adjacent organs to radiation, the effects of radiotherapy are often unsatisfactory. Therefore, it is necessary to study radiosensitization in HCC.

Method

A microarray was used to analyze the genes that were significantly associated with radiosensitivity. HCC cells, HepG2 and MHCC97H, were subjected to radiation in vitro. Real-time PCR was performed to determine MIR22HG (microRNA22 host gene) and miR-22-5p expression levels. Western blotting was performed to determine histone expression levels. A histone deacetylase (HDAC) whole cell assay was used to determine the activity of HDAC2. MTT, colony formation, 5-ethynyl-2′-deoxyuridine, and wound healing assays were performed to examine the function of MIR22HG and miR-22-5p in cellular radiosensitivity. Chromatin immunoprecipitation-PCR was used to confirm that HDAC2 affects the acetylation level of the MIR22HG promoter region. Finally, animal experiments were performed to demonstrate the in vivo effect of MIR22HG on the radiosensitivity of hepatoma.

Results

Irradiation can up-regulate MIR22HG expression and down-regulate HDAC2 expression. Inhibition of HDAC2 expression promotes histone acetylation in the MIR22HG promoter region and up-regulates MIR22HG expression. MIR22HG can increase radiosensitivity via miR-22-5p in HCC.

Conclusion

Inhibition of HDAC2 expression promotes histone acetylation in the MIR22HG promoter region, thereby up-regulating the expression of MIR22HG and promoting the production of miR-22-5p, and ultimately increasing the sensitivity of liver cancer radiotherapy.

Immunogenic Effect of Hyperthermia on Enhancing Radiotherapeutic Efficacy

Hyperthermia is a cancer treatment where tumor tissue is heated to around 40 °C. Hyperthermia shows both cancer cell cytotoxicity and immune response stimulation via immune cell activation. Immunogenic responses encompass the innate and adaptive immune systems, involving the activation of macrophages, natural killer cells, dendritic cells, and T cells. Moreover, hyperthermia is commonly used in combination with different treatment modalities, such as radiotherapy and chemotherapy, for better clinical outcomes. In this review, we will focus on hyperthermia-induced immunogenic effects and molecular events to improve radiotherapy efficacy. The beneficial potential of integrating radiotherapy with hyperthermia is also discussed.

KU-0060648 inhibits hepatocellular carcinoma cells through DNA-PKcs-dependent and DNA-PKcs-independent mechanisms

Here we tested anti-tumor activity of KU-0060648 in preclinical hepatocellular carcinoma (HCC) models. Our results demonstrated that KU-0060648 was anti-proliferative and pro-apoptotic in established (HepG2, Huh-7 and KYN-2 lines) and primary human HCC cells, but was non-cytotoxic to non-cancerous HL-7702 hepatocytes. DNA-PKcs (DNA-activated protein kinase catalytic subunit) is an important but not exclusive target of KU-0060648. DNA-PKcs knockdown or dominant negative mutation inhibited HCC cell proliferation. On the other hand, overexpression of wild-type DNA-PKcs enhanced HepG2 cell proliferation. Importantly, KU-0060648 was still cytotoxic to DNA-PKcs-silenced or -mutated HepG2 cells, although its activity in these cells was relatively weak. Further studies showed that KU-0060648 inhibited PI3K-AKT-mTOR activation, independent of DNA-PKcs. Introduction of constitutively-active AKT1 (CA-AKT1) restored AKT-mTOR activation after KU-0060648 treatment in HepG2 cells, and alleviated subsequent cytotoxicity. In vivo, intraperitoneal (i.p.) injection of KU-0060648 significantly inhibited HepG2 xenograft growth in nude mice. AKT-mTOR activation was also inhibited in xenografted tumors. Finally, we showed that DNA-PKcs expression was significantly upregulated in human HCC tissues. Yet miRNA-101, an anti-DNA-PKcs miRNA, was downregulated. Over-expression of miR-101 in HepG2 cells inhibited DNA-PKcs expression and cell proliferation. Together, these results indicate that KU-0060648 inhibits HCC cells through DNA-PKcs-dependent and -independent mechanisms.

Jujube leaf green tea extracts inhibits hepatocellular carcinoma cells by activating AMPK

Here we evaluated the anti-hepatocellular carcinoma activity by the Jujube leaf green tea extracts (JLGTE). We showed that JLGTE exerted anti-proliferative, cytotoxic and pro-apoptotic activities against HepG2 and primary human hepatocellular carcinoma cells. It was however non-cytotoxic to the normal hepatocytes. JLGTE activated AMP-activated protein kinase (AMPK) signaling, which was required for its cytotoxicity against hepatocellular carcinoma cells. Silence of AMPKα1, via targeted short hairpin RNAs or CRISPR-Cas9 genome editing, inhibited JLGTE-induced AMPK activation and HepG2 cell apoptosis. Further, in-activation of AMPK by a dominant negative AMPKα1 (T172A) also alleviated JLGTE's cytotoxicity against HepG2 cells. On the other hand, forced-activation of AMPK by introduction of a constitutively-active AMPKα1 (T172D) mimicked JLGTE's actions and led to HepG2 cell apoptosis. These results suggest that JLGTE inhibits human hepatocellular carcinoma cells possibly via activating AMPK.

Silencing the Girdin gene enhances radio-sensitivity of hepatocellular carcinoma via suppression of glycolytic metabolism

Background

Radiotherapy has been used increasingly to treat primary hepatocellular carcinoma. Clinically, the main cause of radiotherapy failure is cellular radioresistance, conferred via glycolytic metabolism. Our previous study demonstrated that Girdin is upregulated in primary hepatocellular carcinoma and promotes the invasion and metastasis of tumor cells. However, whether Girdin underlies the radio-sensitivity of hepatocellular carcinoma remains unclear.

Methods

A short hairpin RNA (shRNA) was used to silence CCDC88A (encoding Girdin), and real-time PCR was performed to determine CCDC88A mRNA expression. Then, cell proliferation, colony formation, flow cytometric, scratch, and transwell assays were to examine the influence of Girdin silencing on cellular radiosensitivity. Glycolysis assays were conducted to exam cell glycolysis process. Western blotting was performed to explore the signaling pathway downstream of Girdin. Finally, animal experiments were performed to demonstrate the effect of CCDC88A silencing on the radiosensitivity of hepatoma in vivo.

Results

shRNA-induced Girdin silencing suppressed glycolysis and enhanced the radio-sensitivity of hepatic cell lines, HepG2 and Huh-7. Furthermore, silencing of Girdin inhibited the PI3K/AKT/HIF-1α signaling pathway, which is a central regulator of glycolysis.

Conclusion

Girdin can regulate glycolysis in hepatocellular carcinoma cells through the PI3K/AKT/HIF-1α signaling pathway, which decreases the sensitivity of tumor cells to radiotherapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0580-7) contains supplementary material, which is available to authorized users.

High-biologically effective dose palliative radiotherapy for a tumor thrombus might improve the long-term prognosis of hepatocellular carcinoma: a retrospective study

Background

This study aimed to highlight the type of tumor thrombus and identify the prognostic factors influencing the long-term survival outcomes in patients with hepatocellular carcinoma (HCC) having a tumor thrombus. A tumor thrombus in HCC is associated with poor prognosis.

Methods

Eighty patients diagnosed with HCC having a tumor thrombus between May 2006 and April 2014 were enrolled in this study. Age, gender, clinical characteristics, laboratory findings, Child-Pugh classification, performance status (ECOG), types of tumor thrombi, radiotherapy method, biologically effective dose (BED), and primary treatment method were analyzed to identify the prognostic factors associated with the overall survival (OS) rates. Statistical analyses were performed using SPSS version 19.0.

Results

The median follow-up duration was 24 months (range 6–90). The 1-, 3-, and 5-year OS rates of the patients were 77.6%, 37.6%, and 18.8%, respectively. On univariate analysis, gender, radiotherapy method, BED, types of tumor thrombi, Child-Pugh classification, ECOG, and total bilirubin were associated with OS (P < 0.001, P = 0.001, P = 0.016, P = 0.003, P < 0.001, P < 0.001, P = 0.039, respectively). The prognostic factors for OS in multi-variate analyses were gender (P < 0.001), BED (P = 0.044), Child Pugh classification (P = 0.020), performance status (ECOG) (P = 0.004), and types of tumor thrombi (P = 0.001). The median OS for the high-BED group was better than that for the low-BED groups (42 months vs. 19 months, P = 0.016).

Conclusions

Gender, BED, performance status (ECOG), Child-Pugh classification, and types of tumor thrombi seemed to affect OS, and a stepwise decrease in survival was observed with the types of tumor thrombi ranging from I to IV. High-BED palliative radiotherapy might improve the long-term outcomes for patients with HCC having a tumor thrombus.

Efficacy of three-dimensional conformal radiotherapy combined with transarterial chemoembolization for hepatocellular carcinoma with portal vein tumor thrombus

Objective

The current study aimed to evaluate the efficacy and outcomes of three-dimensional conformal radiotherapy (3DCRT) combined with transarterial chemoembolization (TACE) for treating patients with hepatocellular carcinoma involving portal vein tumor thrombus.

Methods

Between January 2000 and December 2013, a total of 182 hepatocellular carcinoma patients with portal vein tumor thrombus were retrospectively analyzed: 68 patients were treated by 3DCRT alone (group A), 74 by TACE alone (group B), and 40 by a combination of 3DCRT + TACE (group C). The overall survival (OS) of the three groups was compared using the Kaplan–Meier method. The independent predictors of survival were identified using multivariate analysis.

Results

The total effective rate (complete response + partial response) among all patients was 44% (80/182). The objective response rate (complete response + partial response) was higher in group C than in group A or B, but the differences were not significant. OS rates at 1, 2, and 3 years were significantly higher in group C than in group A or B (P<0.05), while OS rates were similar between groups A and B. Multivariate analysis identified serum levels of alpha-fetoprotein <400 ng/mL and the use of 3DCRT + TACE as independent predictors of better OS.

Conclusion

These results suggest that combining 3DCRT with TACE may provide better OS than either technique alone in hepatocellular carcinoma patients with portal vein tumor thrombus.

Synthesis of novel galactose functionalized gold nanoparticles and its radiosensitizing mechanism

BACKGROUND

Biocompatible gold nanoparticles (GNPs) are potentially practical and efficient agents in cancer radiotherapy applications. In this study, we demonstrated that GNPs can significantly modulate irradiation response of hepatocellular carcinoma cells in vitro and investigated the underlying mechanisms. We co-grafted galactose (GAL) targeting hepatocyte specific asialoglycoprotein receptor and Polyethylene Glycol (PEG) onto GNPs surfaces to increase GNPs targeting specificity and stability.

RESULTS

This novel GAL-PEG-GNPs and bare GNPs show similar appearance and cytotoxicity profiles, while more GAL-PEG-GNPs can be effectively uptaken and could enhance cancer cell killing.

CONCLUSION

GAL-PEG-GNPs have better radiosensitization to HepG2. The sensitization mechanism of GAL-PEG-GNPs is related to the apoptotic gene process activated by generation of a large amount of free radicals induced by GNPs.

Hyperthermia-induced radiosensitization in CHO wild-type, NHEJ repair mutant and HR repair mutant following proton and carbon-ion exposure

The DNA repair mechanisms involved in hyperthermia-induced radiosensitization with proton and carbon ion radiation exposure were investigated in the present study. In a previous study, Chinese hamster ovary (CHO) cells were exposed to low linear energy transfer (LET) photon radiation. These cells can be sensitized by hyperthermia as a result of inhibition of homologous recombination (HR) repair. The present study used wild-type, non-homologous end joining (NHEJ) and HR repair-deficient CHO cells to define the contributions of each repair pathway to cellular lethality following hyperthermia-induced hadron radiation sensitization. The cells were exposed to ionizing radiation, followed by hyperthermia treatment (42.5°C for 1 h). Hyperthermia-induced radiosensitization was determined by the colony formation assay and thermal enhancement ratio. HR repair-deficient cells exhibited no hyper-sensitization to X-rays, protons, or low and high LET carbon ions when combined with hyperthermia. Wild-type and NHEJ repair-deficient cells exhibited significant hyperthermia-induced sensitization to low LET photon and hadron radiation. Hyperthermia-induced sensitization to high LET carbon-ion radiation was less than at low LET radiation. Relative biological effectiveness (RBE) between radiation alone and radiation combined with hyperthermia cell groups was not significantly different in any of the cell lines, with the exception of wild-type cells exposed to high LET radiation, which exhibited a lower RBE in the combined group. The present study investigated additional cell lines to confirm the lower RBE observed in DNA repair-deficient cell lines. These findings suggested that hyperthermia-induced hyper-sensitization to hadron radiation is also dependent on inhibition of HR repair, as was observed with photon radiation in a previous study.

The role of radiotherapy in the treatment of hepatocellular carcinoma with portal vein tumor thrombus

The aim of this study was to evaluate the role of radiotherapy in the treatment of hepatocellular carcinoma (HCC) with portal vein tumor thrombosis (PVT) and to determine the prognostic factors for overall survival. Altogether, 106 patients with HCC and PVT referred for radiotherapy between 2004 and 2009 were retrospectively reviewed. A total of 60 Gy in 30 daily fractions was delivered with intensity-modulated radiotherapy techniques. Patient-related and treatment-related factors were analyzed to evaluate their prognostic significance for the overall survival rate. Complete response was noted in 10 patients and partial response in 55 patients. The liver lesions had become resectable after the completion of radiotherapy in 12 patients, and surgery was subsequently performed. One or two courses of transarterial chemoembolization (TACE) were administered to 19 patients following radiotherapy. The 1-year and 2-year overall survival rates were 34.7% and 11%, respectively, and the median survival was 7 months for the entire cohort of patients. Post-radiotherapy treatment modality, response to radiotherapy and JIS score were demonstrated as independent prognostic factors for overall survival (P = 0.003, P < 0.001, P < 0.001, respectively). For patients who received surgical intervention after radiotherapy, the median survival was 30 months and the 2-year overall survival rate was 67%. Radiotherapy achieved a 61.5% objective response rate and prolonged survival in patients with PVT. The liver tumors had become resectable after radiotherapy in 11% of patients. Our results suggested that radiotherapy could offer survival benefits and should be considered as a treatment option for patients with PVT. Radiotherapy could also be considered as a preoperative treatment modality in patients with HCC and PVT.

TLR4-dependent immune response promotes radiation-induced liver disease by changing the liver tissue interstitial microenvironment during liver cancer radiotherapy

Liver tissue interstitial fluid (TIF) a special microenvironment around liver cells, which may play a vital role in cell communication during liver injury. Moreover, toll-like receptor 4 (TLR4) is an important trigger of the immune response that may also play a role in liver injuries, including radiation-induced liver disease (RILD). Therefore, the purpose of this study was to identify the roles of the TLR4-dependent immune response and TIFs in RILD after radiation therapy (RT) for liver cancer. This study consisted of two phases, and in the primary phase, the livers of TLR4 mutant (TLR4(-)) and normal (TLR4(+)) mice were irradiated with 30 Gy. TIF was then obtained from mouse livers and assessed by cytokine array analysis 20 days after irradiation, and cytokines in the TIFs, TLR4 and RILD were analyzed. In the second or validation phase, hepatocytes were isolated from TLR4(+) or TLR4(-) mice irradiated with 8 Gy and were co-cultured with TIFs from mouse livers, apoptosis of the hepatocytes was then measured using flow cytometry. We found that severe RILD was accompanied by higher expression of granulocyte macrophage colony-stimulating factor (GM-CSF), tumor necrosis factor-related apoptosis inducing ligand (TRAIL) and vascular endothelial growth factor receptor 2(VEGFR-2) in liver TIFs, from in TLR4(+) mice compared with TLR4(-) mice (P < 0.05). In both TLR4(+) and TLR4(-) hepatocytes, apoptosis after irradiaton was increased significantly after co-culture in TIFs from TLR4(+) mice that had their livers irradiated, compared with TIFs from TLR4(-) mice that had their livers irradiated or TIFs from unirradiated mice (P < 0.05). In summary, these findings indicate that the TLR4-dependent immune response may promote RILD by enhancing the expression of GM-CSF, VEGFR-2 and TRAIL in liver TIFs.

Molecular targets and mechanisms of radiosensitization using DNA damage response pathways

The cellular reaction to genomic instability includes a network of signal transduction pathways collectively referred to as the DNA damage response (DDR). Activated by a variety of DNA lesions, the DDR orchestrates cell cycle arrest and DNA repair, and initiates apoptosis in instances where damage cannot be repaired. As such, disruption of the DDR increases the prevalence of DNA damage secondary to incomplete repair, and in doing so, enhances radiation-induced cytotoxicity. This article describes the molecular agents and their targets within DDR pathways that sensitize cells to radiation. Moreover, it reviews the therapeutic implications of these compounds, provides an overview of relevant clinical trials and offers a viewpoint on the evolution of the field in the years to come.

A comparison of treatment combinations with and without radiotherapy for hepatocellular carcinoma with portal vein and/or inferior vena cava tumor thrombus

PURPOSE

To evaluate the potential role of external beam radiation therapy (EBRT) in the treatment of patients with hepatocellular carcinoma (HCC) who have portal vein (PV) and/or inferior vena cava (IVC) tumor thrombi.

METHODS AND MATERIALS

One hundred fifty-eight patients with HCC who had PV and/or IVC tumor thrombus were reviewed and analyzed by Kaplan-Meier and Cox regression analysis. Forty-four patients with HCC who received local limited EBRT (in addition to other treatment modalities) were classified as the EBRT group. The total radiation dose was 36-60 Gy (median, 50 Gy) and was focused on the tumor thrombi. One hundred fourteen patients with HCC who did not receive EBRT were selected from hospitalized patients with HCC who had PV and/or IVC thrombi during the same period; these were classified as the non-EBRT group, and their intrahepatic tumors were treated with transarterial chemoembolization or resection, on the basis of the patients' status. Parameters observed included survival rates and the tumor thrombus response to EBRT as seen on CT scan or MRI.

RESULTS

Of the 44 patients who received EBRT, 15 (34.1%) showed complete disappearance of tumor thrombi, 5 (11.4%) were in partial remission, 23 (52.3%) were stable in their tumor thrombi, and 1 (2.3%) showed disease progression at the end of the study period. The median survival was 8 months, and the 1-year survival rate was 34.8% in the EBRT group. In the non-EBRT group, the median survival and 1-year survival rates were 4 months and 11.4%, respectively. In stepwise multivariate analysis, EBRT showed a strongly protective value (relative risk = 0.324, p < 0.001). Survival was not related to intrahepatic tumor status in the non-EBRT patients. However, in the EBRT group, poorer prognosis was significantly related to intrahepatic multifocal or diffusion lesions, and the most common reason for death was liver failure caused by uncontrolled intrahepatic disease.

CONCLUSION

Although EBRT is palliative in intent, it is preferred for prolonging survival in the treatment of tumor thrombi.

Radiosensitization by hyperthermia in the chicken B-lymphocyte cell line DT40 and its derivatives lacking nonhomologous end joining and/or homologous recombination pathways of DNA double-strand break repair

Hyperthermia has a radiosensitizing effect, which is one of the most important biological bases for its use in cancer therapy with radiation. Although the mechanism of this effect has not been clarified in molecular terms, possible involvement of either one or both of two major DNA double-strand break (DSB) repair pathways, i.e. nonhomologous end joining (NHEJ) and homologous recombination (HR), has been speculated. To test this possibility, we examined cells of the chicken B-lymphocyte cell line DT40 and its derivatives lacking NHEJ and/or HR: KU70(-/-), DNA-PKcs(-/-/-), RAD54(-/-) and KU70(-/-)/RAD54(-/-). Radiosensitization by hyperthermia could be seen in all of the mutants, including KU70(-/-)/RAD54(-/-), which lacked both NHEJ and HR. Therefore, radiosensitization by hyperthermia cannot be explained simply by its inhibitory effects, if any, on NHEJ and/or HR alone. However, in NHEJ-defective KU70(-/-) and DNA-PKcs(-/-/-), consisting of two subpopulations with distinct radiosensitivity, the radiosensitive subpopulation, which is considered to be cells in G(1) and early S, was not sensitized. Substantial sensitization was seen only in the radioresistant subpopulation, which is considered to be cells in late S and G(2), capable of repairing DSBs through HR. This observation did not exclude possible involvement of NHEJ in G(1) and early S phase and also suggested inhibitory effects of hyperthermia on HR. Thus partial contribution of NHEJ and HR in radiosensitization by hyperthermia, especially that depending on the cell cycle stage, remains to be considered.