Apoptosis-modulating agents in combination with radiotherapy-current status and outlook

Evading tumor evasion: current concepts and perspectives of anti-angiogenic cancer therapy

Within three decades, anti-angiogenic therapy has rapidly evolved into an integral component of current standard anti-cancer treatment. Anti-angiogenic therapy has fulfilled a number of its earlier proposed promises. The universality of this approach is demonstrated by the broad spectrum of malignant and benign tumor entities, as well as non-neoplastic diseases, that are currently treated with anti-angiogenic agents. In contrast to tumor cell targeting therapies, the development of acquired drug resistance (e.g., via mutations in growth factor receptor signaling genes) has not been described yet for the principal target of anti-angiogenic therapy--the tumor endothelium. Moreover, the tumor endothelium has emerged as a critical target of conventional cancer therapies, such as chemotherapy and radiotherapy. The presumption that tumor growth and metastasis are angiogenesis-dependent implies that the number of potential targets of an anti-cancer therapy could be reduced to those that stimulate the angiogenesis process. Therefore, the set of endogenous angiogenesis stimulants might constitute an "Achilles heel" of cancer. Direct targeting of tumor endothelium via, e.g., endogenous angiogenesis inhibitors poses another promising but clinically less explored therapeutic strategy. Indeed, the majority of current anti-angiogenic approaches block the activity of a single or at most a few pro-angiogenic proteins secreted by tumor cells or the tumor stroma. Based on our systems biology work on the angiogenic switch, we predicted that the redundancy of angiogenic signals might limit the efficacy of anti-angiogenic monotherapies. In support of this hypothesis, emerging experimental evidence suggests that tumors may become refractory or even evade the inhibition of a single pro-angiogenic pathway via compensatory upregulation of alternative angiogenic factors. Here, we discuss current concepts and propose novel strategies to overcome tumor evasion of anti-angiogenic therapy. We believe that early detection of tumors, prediction of tumor evasive mechanisms and rational design of anti-angiogenic combinations will direct anti-angiogenic therapy towards its ultimate goal--the conversion of cancer to a dormant, chronic, manageable disease.

Tumour-targeted delivery of TRAIL using Salmonella typhimurium enhances breast cancer survival in mice

Background:

An effective cancer therapeutic must selectively target tumours with minimal systemic toxicity. Expression of a cytotoxic protein using Salmonella typhimurium would enable spatial and temporal control of delivery because these bacteria preferentially target tumours over normal tissue.

Methods:

We engineered non-pathogenic S. typhimurium to secrete murine TNF-related apoptosis-inducing ligand (TRAIL) under the control of the prokaryotic radiation-inducible RecA promoter. The response of the RecA promoter to radiation was measured using fluorometry and immunoblotting. TRAIL toxicity was determined using flow cytometry and by measuring caspase-3 activation. A syngeneic murine tumour model was used to determine bacterial accumulation and the response to expressed TRAIL.

Results:

After irradiation, engineered S. typhimurium secreted TRAIL, which caused caspase-3-mediated apoptosis and death in 4T1 mammary carcinoma cells in culture. Systemic injection of Salmonella and induction of TRAIL expression using 2 Gy γ-irradiation caused a significant delay in mammary tumour growth and reduced the risk of death by 76% when compared with irradiated controls. Repeated dosing with TRAIL-bearing Salmonella in conjunction with radiation improved the 30-day survival from 0 to 100%.

Conclusion:

These results show the pre-clinical utility of S. typhimurium as a TRAIL expression vector that effectively reduces tumour growth and extends host survival.

AT-101, a small molecule inhibitor of anti-apoptotic Bcl-2 family members, activates the SAPK/JNK pathway and enhances radiation-induced apoptosis

Background

Gossypol, a naturally occurring polyphenolic compound has been identified as a small molecule inhibitor of anti-apoptotic Bcl-2 family proteins. It induces apoptosis in a wide range of tumor cell lines and enhances chemotherapy- and radiation-induced cytotoxicity both in vitro and in vivo. Bcl-2 and related proteins are important inhibitors of apoptosis and frequently overexpressed in human tumors. Increased levels of these proteins confer radio- and chemoresistance and may be associated with poor prognosis. Consequently, inhibition of the anti-apoptotic functions of Bcl-2 family members represents a promising strategy to overcome resistance to anticancer therapies.

Methods

We tested the effect of (-)-gossypol, also denominated as AT-101, radiation and the combination of both on apoptosis induction in human leukemic cells, Jurkat T and U937. Because activation of the SAPK/JNK pathway is important for apoptosis induction by many different stress stimuli, and Bcl-X_L is known to inhibit activation of SAPK/JNK, we also investigated the role of this signaling cascade in AT-101-induced apoptosis using a pharmacologic and genetic approach.

Results

AT-101 induced apoptosis in a time- and dose-dependent fashion, with ED₅₀ values of 1.9 and 2.4 μM in Jurkat T and U937 cells, respectively. Isobolographic analysis revealed a synergistic interaction between AT-101 and radiation, which also appeared to be sequence-dependent. Like radiation, AT-101 activated SAPK/JNK which was blocked by the kinase inhibitor SP600125. In cells overexpressing a dominant-negative mutant of c-Jun, AT-101-induced apoptosis was significantly reduced.

Conclusion

Our data show that AT-101 strongly enhances radiation-induced apoptosis in human leukemic cells and indicate a requirement for the SAPK/JNK pathway in AT-101-induced apoptosis. This type of apoptosis modulation may overcome treatment resistance and lead to the development of new effective combination therapies.

Small-molecule XIAP inhibitors enhance gamma-irradiation-induced apoptosis in glioblastoma

Because evasion of apoptosis can cause radioresistance of glioblastoma, there is a need to design rational strategies that counter apoptosis resistance. In the present study, we investigated the potential of targeting the antiapoptotic protein XIAP for the radiosensitization of glioblastoma. Here, we report that small-molecule XIAP inhibitors significantly enhance gamma-irradiation-induced loss of viability and apoptosis and cooperate with gamma-irradiation to suppress clonogenic survival of glioblastoma cells. Analysis of molecular mechanisms reveals that XIAP inhibitors act in concert with gamma-irradiation to cause mitochondrial outer membrane permeabilization, caspase activation, and caspase-dependent apoptosis. Importantly, XIAP inhibitors also sensitize primary cultured glioblastoma cells derived from surgical specimens as well as glioblastoma-initiating stemlike cancer stem cells for gamma-irradiation. In contrast, they do not increase the toxicity of gamma-irradiation on some nonmalignant cells of the central nervous system, including rat neurons or glial cells, pointing to some tumor selectivity. In conclusion, by demonstrating for the first time that small-molecule XIAP inhibitors increase the radiosensitivity of glioblastoma cells while sparing normal cells of the central nervous system, our findings build the rationale for further (pre)clinical development of XIAP inhibitors in combination with gamma-irradiation in glioblastoma.

NFkappaB signaling related molecular alterations in human neuroblastoma cells after fractionated irradiation

Radiotherapy has been used as an adjunctive local-control modality for high-risk neuroblastoma. However, relapse due to radioresistance affects the success of radiotherapy. Ascertaining the fractionated radiation (FIR) modulated molecular targets is imperative in targeted molecular therapy. Accordingly, we investigated the (i) expression of genes representing six functional pathways; (ii) NFkappaB DNA-binding activity and (iii) expression of radioresponsive molecules after single dose (10 Gy) radiation (SDR) and FIR (2 Gy x 5) in human neuroblastoma cells. Alterations in gene expression were analyzed using QPCR-profiling, NFkappaB activity using electrophoretic mobility shift assay (EMSA) and pIkappaBalpha using immunoblotting. Modulations in TNFalpha, IL-1alpha, pAKT, IAP1, IAP2, XIAP, survivin, MnSOD, BID, Bak, MyD88 and Vegfc were determined using quantitative real-time PCR (Q-PCR) and immunoblotting. Compared to SDR, FIR significantly induced the expression of 25 genes and completely suppressed another 30 genes. Furthermore, FIR induced NFkappaB-DNA-binding activity and IkappaBalpha phosphorylation. Similarly, we observed an induced expression of IAP1, IAP2, XIAP, Survivin, IL-1alpha, MnSOD, Bid, Bak, MyD88, TNFalpha and pAKT in cells exposed to FIR. The results of the study clearly show distinct differences in the molecular response of cells between SDR and FIR. We identified several potential targets confining to NFkappaB signaling cascade that may affect radio-resistance after FIR.

Combined action of celecoxib and ionizing radiation in prostate cancer cells is independent of pro-apoptotic Bax

BACKGROUND AND PURPOSE

The cyclooxygenase-2-inhibitor celecoxib has been shown to inhibit cell growth and to reduce prostatic intraepithelial neoplasia in mice. The drug was suggested to increase efficacy of ionizing radiation. However, extent and mechanisms of the suggested benefit of celecoxib on the radiation response are still unclear. The aim of the present study was to analyze cytotoxic efficacy of celecoxib in combination with irradiation on human prostate cancer cell lines and to define the importance of pro-apoptotic Bax in this process.

MATERIALS AND METHODS

Induction of apoptosis and global and clonogenic cell survival upon irradation- (2-10Gy), celecoxib- (10-75microM) or combined treatment were evaluated in prostate cancer cells by fluorescence microscopy, WST-1 assay and standard colony formation assays.

RESULTS

Celecoxib <25microM caused morphological changes and growth inhibition without substantial apoptosis or radiosensitization in terms of decreased clonogenic cell survival. In contrast, celecoxib 25microM increased radiation-induced cell death and clonogenic kill. While radiation-induced clonogenic death was increased in the presence of Bax, effects of celecoxib or combined treatment were Bax independent.

CONCLUSIONS

Our findings reveal Bax-independent beneficial effects of celecoxib on radiation-induced apoptosis and eradication of clonogenic prostate cancer cells in vitro providing a rationale for clinical evaluation of high-dose celecoxib in combination with irradiation in prostate cancer patients.

Increased apoptotic potential and dose-enhancing effect of gold nanoparticles in combination with single-dose clinical electron beams on tumor-bearing mice

High atomic number material, such as gold, may be used in conjunction with radiation to provide dose enhancement in tumors. In the current study, we investigated the dose-enhancing effect and apoptotic potential of gold nanoparticles in combination with single-dose clinical electron beams on B16F10 melanoma tumor-bearing mice. We revealed that the accumulation of gold nanoparticles was detected inside B16F10 culture cells after 18 h of incubation, and moreover, the gold nanoparticles were shown to be colocalized with endoplasmic reticulum and Golgi apparatus in cells. Furthermore, gold nanoparticles radiosensitized melanoma cells in the colony formation assay (P = 0.02). Using a B16F10 tumor-bearing mouse model, we further demonstrated that gold nanoparticles in conjunction with ionizing radiation significantly retarded tumor growth and prolonged survival compared to the radiation alone controls (P < 0.05). Importantly, an increase of apoptotic signals was detected inside tumors in the combined treatment group (P < 0.05). Knowing that radiation-induced apoptosis has been considered a determinant of tumor responses to radiation therapy, and the length of tumor regrowth delay correlated with the extent of apoptosis after single-dose radiotherapy, these results may suggest the clinical potential of gold nanoparticles in improving the outcome of melanoma radiotherapy.

Gamma-radiation induces apoptosis via sarcoplasmatic reticulum in guinea pig ileum smooth muscle cells

We investigated the effects of gamma-radiation on cells isolated from the longitudinal smooth muscle layer of the guinea pig ileum, a relatively radioresistant tissue. Single doses (up to 50 Gy) reduced the amount of sarcoplasmatic reticulum and condensed the myofibrils, as shown by electron microscopy 3 days post-irradiation. After that, contractility of smooth muscle strips was reduced. Ca(2+) handling was altered after irradiation, as shown in fura-2 loaded cells, with elevated basal intracellular Ca(2+), reduced amount of intrareticular Ca(2+), and reduced capacitive Ca(2+) entry. Radiation also induced apoptosis, judged from flow cytometry of cells loaded with proprium iodide. Electron microscopy showed that radiation caused condensation of chromatin in dense masses around the nuclear envelope, the presence of apoptotic bodies, fragmentation of the nucleus, detachment of cells from their neighbors, and reductions in cell volume. Radiation also caused activation of caspase 12. Apoptosis was reduced by the administration of the caspase inhibitor Z-Val-Ala-Asp-fluoromethyl-ketone methyl ester (Z-VAD-FMK) during the 3 day period after irradiation, and by the chelator of intracellular Ca(2+), 1,2-bis(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid (BAPTA), from 1 h before until 2 h after irradiation. BAPTA also reduced the effects of radiation on contractility, basal intracellular Ca(2+), amount of intrareticular Ca(2+), capacitative Ca(2+) entry, and apoptosis. In conclusion, the effects of gamma radiation on contractility, Ca(2+) handling, and apoptosis appear due to a toxic action of intracellular Ca(2+). Ca(2+)-induced damage to the sarcoplasmatic reticulum seems a key event in impaired Ca(2+) handling and apoptosis induced by gamma-radiation.

Enhancement of glioma radiotherapy and chemotherapy response with targeted antibody therapy against death receptor 5

PURPOSE

TRA-8 is an agonistic mouse monoclonal antibody that binds to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor 5, which induces apoptosis in cancer cells through a caspase-8-dependent mechanism. We investigated the ability of TRA-8 to augment the radiotherapy (RT) and chemotherapy response of human glioma cells in vitro and in vivo.

METHODS AND MATERIALS

The in vitro cytotoxicity of TRA-8 and temozolomide (Tmz) or RT was examined using adenosine triphosphate-dependent viability and clonogenic survival assays with five glioma cell lines. Death receptor 5 expression was determined by flow cytometry. In vivo studies included subcutaneous and intracranial xenograft models testing various combination treatments, including RT, Tmz, and TRA-8.

RESULTS

TRA-8, combined with Tmz or RT, produced enhanced cytotoxicity against five glioma cell lines compared with the use of the individual agents alone. Death receptor 5 upregulation occurred in response to RT. Complete tumor regression in the subcutaneous experiments was the most common in animals that received combination therapy with TRA-8/Tmz/RT. TRA-8 enhanced tumor growth delay in combination with RT or Tmz. TRA-8 alone had limited activity against intracranial tumors. In contrast, the median survival of mice treated with TRA-8/Tmz/RT was significantly greater than the control or TRA-8-alone-treated mice. The median survival of the mice treated with TRA-8/Tmz/RT or chemoradiotherapy only was significantly greater than the control or TRA-8-treated mice. A trend toward improved survival was observed between TRA-8/Tmz/RT-treated and Tmz/RT-treated mice.

CONCLUSIONS

These preliminary findings support the hypothesis that TRA-8 will augment the RT and chemotherapy response in gliomas. A humanized version of TRA-8 is being evaluated in a Phase II clinical trial.

Maintenance of manganese superoxide dismutase (SOD2)-mediated delayed radioprotection induced by repeated administration of the free thiol form of amifostine

Thiol-containing drugs such as WR1065, the free thiol form of amifostine, have been shown to induce a delayed radioprotective effect in both malignant and non-malignant cells. In mammalian cells exposed to a dose as low as 40 microM WR1065, the redox-sensitive nuclear transcription factor kappaB (NFkappaB) is activated, leading to an elevation in the expression of the antioxidant gene manganese superoxide dismutase (SOD2) and a concomitant increase in active SOD2 enzyme levels that peaks 24 to 32 h later. Exposure of cells to ionizing radiation during the period of elevated SOD2 enzymatic activity results in an enhanced radiation resistance. This is seen as an increase in surviving fraction as determined by standard colony formation assays. To determine whether this delayed radioprotection can be maintained over a prolonged period in cells of either malignant or non-malignant origin, both human microvascular endothelial cells (HMEC) and SA-NH mouse sarcoma cells were grown to confluence and exposed to 40 muM WR1065 using three administration protocols: (1) daily drug exposure for 10 days followed each day by irradiation with 2 Gy; (2) drug exposure once every 48 h followed by irradiation with 2 Gy 48 h later for 14 days; and (3) drug exposure every 72 h followed by irradiation with 2 Gy 72 h later for 12 days. As a function of each experimental condition, cell numbers and associated SOD2 enzymatic activities were measured at the time of each irradiation. None of the treatment conditions were toxic to either HMEC or SA-NH cells. SOD2 activity was elevated 5.3- and 1.8-fold over background on average for HMEC exposed to 40 microM WR1065 every 24 or 48 h, respectively. Likewise, SOD2 activity was elevated in SA-NH mouse sarcoma cells 7.8- and 4.9-fold after daily exposure to WR1065 or exposure to WR1065 once every 48 h, respectively. Both HMEC and SA-NH cells exhibited enhanced radiation resistance that correlated with the increase in SOD2 activity. The average respective increases in cell survival were 1.33 +/- 0.01 (SEM), 1.23 +/- 0.01 and 1.04 +/- 0.01 for HMEC exposed to WR1065 every 24, 48 and 72 h, respectively, and 1.27 +/- 0.01, 1.18 +/- 0.02 and 1.02 +/- 0.02 for SA-NH cells exposed to WR1065 every 24, 48 and 72 h, respectively. Both the elevation in WR1065-induced SOD2 enzymatic activity and the corresponding increase in radiation resistance were completely inhibited in HMEC and SA-NH cells transfected with human or mouse SOD2 siRNA oligomers and irradiated 24 h later. These data demonstrate that a delayed radioprotective effect can be induced and maintained over a prolonged period in both non-malignant and malignant cells exposed to thiol-containing drugs such as WR1065. For non-malignant cells this represents a novel paradigm for radiation protection. The ability of WR1065 to induce a persistent elevated radiation resistance in malignant cells, however, suggests a new potential concern regarding the issue of tumor protection in patients exposed to thiol-containing drugs.

Examination of the cellular mechanisms by which marinobufagenin inhibits cytotrophoblast function

Marinobufagenin (MBG) is an endogenous mammalian cardiotonic steroid involved in the inhibition of Na(+)/K(+)-ATPase. Increased plasma levels have been reported in patients with volume expansion-related hypertension. We have recently demonstrated that MBG impairs first trimester cytotrophoblast (CTB) cell proliferation, migration, and invasion, which may play a role in the development of preeclampsia. However, whether apoptosis contributes to altered CTB cell function by MBG remains unknown. Using the human extravillous CTB cell line SGHPL-4, we examined the effect of MBG and a similar Na(+)/K(+)-ATPase inhibitor, ouabain, on the phosphorylation status of Jnk, p38, and Src. Additionally, we measured apoptosis by caspase 9 and 3/7 activity and by annexin-V staining. We also investigated interleukin-6 (IL-6) secretion with or without p38 and Jnk inhibition. MBG significantly increased the phosphorylation of Jnk, p38, and Src and increased the expression of caspase 9 and 3/7 indicating the activation of apoptosis. MBG treatment also stimulated the expression of the early apoptosis marker, annexin-V, which was prevented by Jnk and p38 inhibition. MBG also stimulated the secretion of IL-6, which was attenuated by p38 inhibition. Ouabain had similar effects to those of MBG, suggesting that the apoptotic effects on CTB cells may be mediated by inhibition of Na(+)/K(+)-ATPase. In conclusion, the MBG-induced impairment of CTB function occurs via activation of Jnk, p38, and Src leading to increased apoptosis and IL-6 secretion. These observations may have clinical applicability with respect to the therapy of preeclampsia.

Inhibitors of DNA polymerase beta: activity and mechanism

Bioassay-guided fractionation of extracts prepared from Couepia polyandra and Edgeworthia gardneri resulted in the isolation of the DNA polymerase beta (pol beta) inhibitors oleanolic acid (1), edgeworin (2), betulinic acid (3), and stigmasterol (4). Study of these pol beta inhibitors revealed that three of them inhibited both the lyase and polymerase activities of DNA polymerase beta, while stigmasterol inhibited only the lyase activity. Further investigation indicated that the four inhibitors had substantially different effects on the DNA-pol beta binary complex that is believed to be an obligatory intermediate in the lyase reaction. It was found that the inhibitors potentiated the inhibitory action of the anticancer drug bleomycin in cultured A549 cells, without any influence on the expression of pol beta in the cells. The results of the unscheduled DNA synthesis assay support the thesis that the potentiation of bleomycin cytotoxicity by DNA pol beta inhibitors was a result of an inhibition of DNA repair synthesis.

X irradiation combined with TNF alpha-related apoptosis-inducing ligand (TRAIL) reduces hypoxic regions of human gastric adenocarcinoma xenografts in SCID mice

Our previous study showed that X irradiation induced the expression of death receptor DR5 on the cell surface in tumor cell lines under not only normoxia but also hypoxia. X irradiation combined with TNF alpha-related apoptosis-inducing ligand (TRAIL), which is the ligand of DR5, induced apoptosis in vitro (Takahashi et al., (2007) Journal of Radiation Research, 48: 461-468). In this report, we examined the in vivo antitumor efficacy of X irradiation combined with TRAIL treatment in tumor xenograft models derived from human gastric adenocarcinoma MKN45 and MKN28 cells in SCID mice. X irradiation combined with TRAIL synergistically suppressed the tumor growth rates in the xenograft models derived from MKN45 and MKN28 cells, which have wild type Tp53 and mutated Tp53, respectively, indicating that the antitumor effects occurred in a Tp53-independent manner. Histological analysis showed that the combination of X irradiation and TRAIL induced caspase-3-dependent apoptotic cell death. Moreover, the immunohistochemical detection of hypoxic regions using the hypoxic marker pimonidazole revealed that caspase-3-dependent apoptosis occurred in the hypoxic regions in the tumors. These results indicated that X irradiation combined with TRAIL may be a useful treatment to reduce tumor growth in not only normoxic but also hypoxic regions.

Calreticulin, a molecular chaperone in the endoplasmic reticulum, modulates radiosensitivity of human glioblastoma U251MG cells

Radiotherapy is the primary and most important adjuvant therapy for malignant gliomas. Although the mechanism of radiation resistance in gliomas has been studied for decades, it is still not clear how the resistance is related with functions of molecular chaperones in the endoplasmic reticulum. Calreticulin (CRT) is a Ca(2+)-binding molecular chaperone in the endoplasmic reticulum. Recently, it was reported that changes in intracellular Ca(2+) homeostasis play a role in the modulation of apoptosis. In the present study, we found that the level of CRT was higher in neuroglioma H4 cells than in glioblastoma cells (U251MG and T98G), and was well correlated with the sensitivity to gamma-irradiation. To examine the role of CRT in the radiosensitivity of malignant gliomas, the CRT gene was introduced into U251MG cells, which express low levels of CRT, and the effect of overexpression of CRT on the radiosensitivity was examined. The cells transfected with the CRT gene exhibited enhanced radiation-induced apoptosis compared with untransfected control cells. In CRT-overexpressing cells, cell survival signaling via Akt was markedly suppressed. Furthermore, the gene expression of protein phosphatase 2Ac alpha (PP2Ac alpha), which is responsible for the dephosphorylation and inactivation of Akt, was up-regulated in CRT-overexpressing cells, and the regulation was dependent on Ca(2+). Thus, overexpression of CRT modulates radiation-induced apoptosis by suppressing Akt signaling through the up-regulation of PP2Ac alpha expression via altered Ca(2+) homeostasis. These results show the novel mechanism by which CRT is involved in the regulation of radiosensitivity and radiation-induced apoptosis in malignant glioma cells.

Effectiveness of gene expression profiling for response prediction of rectal cancer to preoperative radiotherapy

BACKGROUND

Our aim was to determine whether the expression levels of specific genes could predict clinical radiosensitivity in human colorectal cancer.

METHODS

Radioresistant colorectal cancer cell lines were established by repeated X-ray exposure (total, 100 Gy), and the gene expressions of the parent and radioresistant cell lines were compared in a microarray analysis. To verify the microarray data, we carried out a reverse transcriptase-polymerase chain reaction analysis of identified genes in clinical samples from 30 irradiated rectal cancer patients.

RESULTS

A comparison of the intensity data for the parent and three radioresistant cell lines revealed 17 upregulated and 142 downregulated genes in all radioresistant cell lines. Next, we focused on two upregulated genes, PTMA (prothymosin alpha) and EIF5a2 (eukaryotic translation initiation factor 5A), in the radioresistant cell lines. In clinical samples, the expression of PTMA was significantly higher in the minor effect group than in the major effect group (P = 0.004), but there were no significant differences in EIF5a2 expression between the two groups.

CONCLUSIONS

We identified radiation-related genes in colorectal cancer and demonstrated that PTMA may play an important role in radiosensitivity. Our findings suggest that PTMA may be a novel marker for predicting the effectiveness of radiotherapy in clinical cases.

Lipid rafts and metabolic energy differentially determine uptake of anti-cancer alkylphospholipids in lymphoma versus carcinoma cells

Perifosine is a member of the class of synthetic alkylphospholipids (APLs) and is being evaluated as anti-cancer agent in several clinical trials. These single-chain APLs accumulate in cellular membranes and disturb lipid-dependent signal transduction, ultimately causing apoptosis in a variety of tumor cells. The APL prototype edelfosine was previously found to be endocytosed by S49 mouse lymphoma cells via lipid rafts. An edelfosine-resistant cell variant, S49(AR), was found to be cross-resistant to other APLs, including perifosine. This resistance was due to defective synthesis of the raft constituent sphingomyelin, which abrogated APL cellular uptake. Sensitivity of S49 cells to edelfosine was higher than perifosine, which correlated with a relatively higher uptake. Human KB epidermal carcinoma cells were much more sensitive to APLs than S49 cells. Their much higher APL uptake was highly dependent on intracellular ATP and ambient temperature, and was blocked by chlorpromazine, independent of canonical endocytic pathways. We found no prominent role of lipid rafts for APL uptake in these KB cells; contrary to S49(AR) cells, perifosine-resistant KBr cells display normal sphingomyelin synthesis, whereas APL uptake by the responsive KB cells was insensitive to treatment with methyl-beta-cyclodextrin, a cholesterol-sequestrator and inhibitor of raft-mediated endocytosis. In conclusion, different mechanisms determine APL uptake and consequent apoptotic toxicity in lymphoma versus carcinoma cells. In the latter cells, APL uptake is mainly determined by a raft- and endocytosis-independent process, but metabolic energy-dependent process, possibly by a lipid transporter.

Targeting Integrins and PI3K/Akt-Mediated Signal Transduction Pathways Enhances Radiation-Induced Anti-angiogenesis

The integrins and PI3K/Akt are important mediators of the signal transduction pathways involved in tumor angiogenesis and cell survival after exposure to ionizing radiation. Selective targeting of either integrins or PI3K/Akt can radiosensitize tumors. In this study, we tested the hypothesis that the combined inhibition of integrin alphanubeta3 by cRGD and PI3K/Akt by LY294002 would significantly enhance radiation-induced inhibition of angiogenesis by vascular endothelial cells. Treatment with cRGD inhibited the adhesion and tube formation of human umbilical vein endothelial cells (HUVECs). The inhibitory effect was further increased when cRGD and LY294002 were applied simultaneously. Both radiation and cRGD induced Akt phosphorylation, up-regulated COX2 expression, and increased PGE2 production in HUVECs. Treatment with LY294002 effectively inhibited radiation- and cRGD-induced Akt phosphorylation and up-regulation of COX2 and increased apoptosis of HUVECs. The combined use of cRGD and LY294002 enhanced radiation-induced cell killing. The clonogenic survival of HUVECs was decreased from 34% with 2 Gy radiation to 4% with these agents combined. These results demonstrate that combined use of ionizing radiation, cRGD and LY294002 inhibited multiple signaling transduction pathways involved in tumor angiogenesis and enhanced radiation-induced effects on vascular endothelial cells.

α- and ϵ-Protein Kinase C Activity during Smooth Muscle Cell Apoptosis in Response to γ-Radiation

The use of gamma-radiation in treatment of pelvic cancer is associated with injury of healthy surrounding tissues and disorders of intestinal motility; however, the cellular mechanisms involved are unclear. We tested the hypothesis that exposure of visceral smooth muscle cells (SMCs) to gamma-radiation induces apoptosis via activation of specific protein kinase C (PKC) isoforms. Cultured SMCs and slices from guinea pig ileum smooth muscle longitudinal layer (GPISMLL) were exposed to 10 to 50 Gy. Flow cytometry in gamma-radiated SMCs showed increased percentage of cells in the sub-G(0)/G(1) phase, a hallmark of apoptosis. gamma-Radiation-induced reduction in cell survival was partially but significantly alleviated with the PKC inhibitors. Sections of gamma-irradiated GPISMLL showed DNA fragmentation and apoptotic bodies analyzed by the terminal deoxynucleotidyl transferase dUTP nick-end labeling method, whereas the plasma and nuclear membranes were preserved. Confocal microscopy in gamma-radiated SMCs labeled with annexin V-fluorescein showed an increase in apoptotic cells and phosphatidylserine externalization. Contraction of GPISMLL strips in response to KCl and acetylcholine was reduced in tissues exposed to 30 and 50 Gy. gamma-Radiation of GPISMLL caused an increase in PKC activity in the particulate fraction, a decrease in the cytosolic fraction, and increased particulate/cytosolic PKC activity ratio. Western blot analysis revealed significant amounts of alpha- and epsilon-PKC in the cytosolic fraction of control GPISMLL. gamma-Radiation caused an increase in the amount of alpha- and epsilon-PKC in the particulate fraction and a decrease in the cytosolic fraction. Data suggest that gamma-radiation induces apoptosis, growth arrest, and contractile dysfunction in visceral SMCs of GPISMLL via activation and translocation of alpha- and epsilon-PKC isoforms.

Chemoradiotherapy for localized esophageal cancer: regimen selection and molecular mechanisms of radiosensitization

Concurrent chemoradiotherapy administered either before surgery or as definitive treatment has a central role in the multimodality treatment of locally advanced esophageal cancer. Initial studies of this combined-modality regimen were based on models of squamous-cell cancers from other primary sites; this approach progressed from use of bleomycin or fluorouracil plus cisplatin concurrent with radiation in early trials, to the integration of taxanes, camptothecins and platinum analogs in recent trials. These trials demonstrated the tumoricidal effect of concurrent chemotherapy and radiotherapy and showed the survival advantages of this approach. Preoperative concurrent chemoradiation is used to downstage the tumor, ideally to a pathological complete response status in which there is no residual tumor in the resected primary and nodal tissues. A pathological complete response is associated with long-term survival but occurs in a minority (30%) of patients. While clinical trials have demonstrated an improvement in survival with concurrent chemoradiotherapy this effect is limited, as indicated by the plateau in survival beyond 5 years of approximately 30% or less. The recent clinical development of biologic, targeted therapies provides a new avenue for the study of chemoradiotherapy and an opportunity to increase long-term survival.

Sensitization of chronic lymphocytic leukemia cells to TRAIL-induced apoptosis by hyperthermia

We recently reported that, in cultured leukemic T lymphocytes and promyelocytic cells, a mild heat shock treatment (1 h at 42 degrees C) induced a long lasting stimulation of the apoptosis induced by TNF-related apoptosis inducing ligand (TRAIL). On the opposite, no effects were recorded toward normal human T lymphocytes. The apoptogenic efficiency of TRAIL in leukemic lymphocytes is linked to the long lasting increased ability of TRAIL to recognize and bind DR4 and DR5 receptors during hyperthermia. Here, we have analyzed whether this new apoptotic co-treatment could be relevant toward primary cells from patients suffering of chronic lymphocytic leukemia. Analysis of samples from 24 patients with different ages, sex and disease stages revealed that half of them had lymphocytes that, once isolated and analyzed in vitro, positively responded (increase of cell death) to the heat shock plus TRAIL co-treatment. Analysis of the level of expression of various anti-apoptotic proteins in the cell samples revealed a great heterogeneity between patients and no clear relationships could be drawn. Nevertheless, most cell samples that were sensitive to TRAIL plus heat shock induced apoptosis displayed a higher level of cell surface DR4 and DR5 receptors than the non-sensitive counterparts. Hence, analysis of the level of TRAIL surface receptors is a prerequisite for future clinical applications based on this protocol.

Enhancement of hyperthermia-induced apoptosis by a new synthesized class of furan-fused tetracyclic compounds

The combined effects of hyperthermia (44 degrees C, 20 min) or X-rays (10 Gy) and a new class of furan-fused tetracyclic synthesized compounds (DFs), on apoptosis in human lymphoma U937 cells were investigated. Among the tested compounds (DF1 approximately 6), the combined treatment of 10 microM DF with TIPS (triisopropylsilyloxy) (Designated #3 DF3) and hyperthermia showed the largest potency to induce DNA fragmentation at 6 h after hyperthermia but no enhancement was observed if it was combined with X-rays. Enhancement of hyperthermia-induced apoptosis by DF3 in a dose-dependent manner was observed. When the cells were treated first with DF3 at a nontoxic concentration of 20 microM, and exposed to hyperthermia afterwards, a significant enhancement of heat-induced apoptosis was evidenced by DNA fragmentation, morphological changes and phosphatidylserine externalization. The activation of Bid, but no change of Bax and Bcl-2 were observed after the combined treatment. The release of cytochrome c from mitochondria to cytosol, which was induced by hyperthermia, was enhanced by DF3. Mitochondrial transmembrane potential was decreased and the activation of caspase-3 and caspase-8 was enhanced in the cells treated with the combination. Externalization of Fas was observed following the combined treatment. Flow cytometry revealed rapid and sustained increase of intracellular superoxide due to DF3, and showed subsequent and transient increase in the formation of intracellular hydrogen peroxide (H(2)O(2)), which was further increased when hyperthermia was combined. These results indicate that the intracellular superoxide and H(2)O(2) generated by DF3 enhance the hyperthermia-induced apoptosis via the Fas-mediated mitochondrial caspase-dependent pathway.

Can radiation-induced apoptosis be modulated by inhibitors of energy metabolism?

PURPOSE

To determine the effect of the inhibitors of energy metabolism, 2-deoxyglucose (2DG) and sodium azide, on radiation-induced apoptosis.

MATERIALS AND METHODS

Radiation-induced apoptosis was determined in U937 monocytic leukaemia cells exposed to energy inhibitors post-irradiation. Apoptosis was scored microscopically using morphological criteria. Glycolysis was determined by assessing glucose consumption and lactate production. Adenine nucleotide levels were measured using a luciferase assay after enzymatic conversion to ATP. Respiration was measured using a Clark-type oxygen electrode.

RESULTS

In addition to their apoptosis-inducing properties, both 2DG and azide modified post-irradiation apoptosis. 2DG induced apoptotic radiosensitization after exposure to lower concentrations (5 mM, 10 mM) up to 20 h post-irradiation while a level of radioprotection was found after 5 h exposure to higher doses up to 100 mM. By contrast, all doses of azide examined (5-50 mM) induced apoptotic radioprotection at all times examined. Glycolytic flux and ATP levels fell rapidly with increasing 2DG dose but energy charge remained unchanged. Glycolysis was less influenced by azide, with ATP levels being initially maintained after exposure but decreasing in a dose-dependent manner at 3 h post-irradiation. However, energy charge was unaffected by azide at the concentrations examined.

CONCLUSIONS

Both 2DG and azide can influence radiation-induced apoptosis possibly through their effects on glycolysis and ATP levels. We suggest that modulation of energy metabolism provides mechanistic insight into radiation-induced apoptotic pathways.

Rationale and clinical application of alkylphospholipid analogues in combination with radiotherapy

Concurrent treatment with radiotherapy and chemotherapy has emerged as an effective strategy to improve clinical outcome of cancer. In addition to combining radiation with classical anticancer agents, several new biological response modifiers are under investigation in pre-clinical and clinical studies. Synthetic alkylphospholipids are anticancer agents that in contrast to most anticancer drugs, do not target DNA, but insert in the plasma membrane and subsequently induce a broad range of biological effects, ultimately leading to cell death. Alkylphospholipids kill tumor cells directly by induction of both apoptotic and non-apoptotic cell death, and indirectly by interference with critical signal transduction pathways involved in phospholipid metabolism and survival. Due to their distinct mode of action, these drugs are considered as attractive candidates to combine with radiotherapy. In this review, we will discuss several alkylphospholipids that reached clinical application. These include first-generation alkyl-lysophospholipids edelfosine and ilmofosine, second-generation alkylphosphocholine-prototype miltefosine and more recently developed analogues perifosine and erucylphosphocholine. We focus on mechanisms of action and the rationale to combine these agents with radiotherapy. The preclinical results on molecular targeting underlying this approach will be reviewed, concluded with first clinical data on combined treatment of radiotherapy with perifosine.

Supernatant of bacterial fermented soybean induces apoptosis of human hepatocellular carcinoma Hep 3B cells via activation of caspase 8 and mitochondria

SC-1, the aqueous phase of soybean fermentation products by bacteria (Bacillus subtilis and Bacillus brevis), significantly inhibited the growth and clonogenesity of human hepatocellular (Hep 3B), mouse hepatocellular (ML-1), and human colorectal (HCT 116 and HT-29) carcinoma cells. Cytotoxicity of SC-1 in Hep 3B cells was through the process of apoptosis characterizing by increase in cell population of sub-G(1) phase, fragmentation of DNA, and change of nuclear morphology. Treatment of Hep 3B cells with SC-1 activated caspase 8 and caspase 3. Elevation of nuclear DNA fragmentation factor 40 (DFF40) and cleavage form of poly(ADP-ribose) polymerase (PARP) were also observed. SC-1 also activated intrinsic pathway via increase of pro-apoptotic (tBid, Bak and Bax) and decrease of anti-apoptotic (Bcl-2 and Bcl-x(L)) proteins on mitochondria, disruption of mitochondrial membrane potential, release of cytochrome c and Smac (second mitochondria-derived activator of caspase/direct IAP binding protein with low PI) from mitochondria, and activation of caspase 9. Inhibition on protein expression of Ku70 in cytosol and cyclooxygenase (COX)-2, but not COX-1, in whole cell lystes were revealed in SC-1-treated Hep 3B cells. These results suggest caspase 8, Ku70 and mitochondria are involved in the antitumor mechanism of SC-1 in Hep 3B cells.

Overexpression of GLUT-1 is associated with resistance to radiotherapy and adverse prognosis in squamous cell carcinoma of the oral cavity

This study tested the hypothesis that GLUT-1 is a marker of radioresistance in oral squamous cell carcinomas (OSCC). A GLUT-1 labeling index (LI) was determined by immunohistochemistry in 40 pretreatment OSCC biopsies. Radiation responses were categorized by histopathology of the resection specimens. Associations between the LI and radiation response, Kaplan-Meier survival estimates and Cox regression analysis for the variables GLUT-1, T-stage, N-stage and chemotherapy were examined. The median LI was 64.2% (range 14-100%). Tumors with >65% of GLUT-1+cells were more resistant to radiation (p=0.023). Overall survival was higher (p=0.044) for subjects with low LI (<median value) than those with high LI (>median value). The Cox regression analysis confirmed the prognostic significance of GLUT-1. Our results indicate that pre-treatment GLUT-1 expression in the tumor is a marker of radioresistance in OSCC, with high expression being associated with poor radiation response and shorter survival.

Fractionated and acute irradiation induced signaling in a murine tumor

The effect of fractionated doses of Co(60) gamma-irradiation (2 Gy per fraction over 5 days), as is delivered in cancer radiotherapy, was compared with acute doses of 10 and 2 Gy, in a serially transplanted mouse fibrosarcoma grown in Swiss mice. The aspects that were studied included the three major mitogen-activated protein (MAP) kinases, namely p44 MAP kinase, p38 MAP kinase, and stress-activated protein (SAP) kinase, which are known to be involved in determining the cell fate following exposure to ionizing radiation. The response of dual specificity phosphatase PAC1 which is involved in the dephosphorylation of MAP kinases was also looked at. There were significant differences in the response to different dose regimens for all the factors studied. Fractionated irradiation elicited an adaptive response with a sustained activation over 7 days of prosurvival p44 MAP kinase which was balanced by the increased activation of proapoptotic p54 SAP kinase up to 1 day post-irradiation, whereas, phosphorylated p38 MAP kinase showed a decrease at most time points. PAC1 was induced following fractionated irradiation and may be acting as a feed back regulator of p44 MAP kinase. The activation of SAP kinase after fractionated irradiation may be a stress response, whereas, constitutively activated p44 MAP kinase may play an important role in the induction of radioresistance during fractionated radiotherapy of cancer and may serve as a promising target for specific inhibitors to enhance the efficacy of radiotherapy.

Does the tumor microenvironment influence radiation-induced apoptosis?

Cytotoxic anti-cancer agents induce apoptosis in tumor and normal tissues. Therefore, it is important to investigate which factors determine these apoptotic processes and hence their likely impact on therapeutic gain. Radiation-induced apoptosis in tumors may be inhibited due to mutations of apoptotic elements or to tumor microenvironmental conditions arising from vascular insufficiency. Tumors typically contain regions of hypoxia, low glucose and acidosis. Hypoxic cells compromise treatment partly because of reduced fixation of damage during radiotherapy and partly because they promote a more malignant phenotype. There is also evidence that hypoxia may inhibit apoptosis. For some cell types, concurrent hypoxia may modulate radiation-induced apoptosis while, for others, post-irradiation hypoxia may be required. This may reflect the activity of different apoptotic pathways. Pathways involving mitochondrial components as well as regulation of SAPK and Fas have been implicated. In addition, several key stages in apoptosis are sensitive to depletion of cellular energy reserves, which results from hypoxia and low glucose conditions. There is also evidence that low pH in tumors can interfere with radiation-induced apoptosis, partly through cell cycle arrest and other undefined mechanisms.

CONCLUSIONS

Hypoxia, low glucose and acidosis influence radiation-induced apoptosis and thus may be detrimental to radiotherapy.

Phase I and pharmacokinetic study of combined treatment with perifosine and radiation in patients with advanced solid tumours

PURPOSE

Perifosine is an orally applicable, membrane-targeted alkylphosphocholine analogue with antitumour activity and radiosensitising properties in preclinical models. The purpose of this phase I study was to determine the feasibility and tolerability of concurrent daily perifosine and radiation in patients with advanced cancer.

PATIENTS AND METHODS

Starting dose of perifosine was 50 mg/day; dose escalation was in steps of 50mg. Daily administration commenced 2 days before radiotherapy and was continued throughout the radiation treatment. At least three patients were entered at each dose level; at the 150 mg/day level 10 patients were included. Pharmacokinetic sampling was performed weekly pre-dosing. Twenty-one patients were entered. Tumour types included NSCLC (n=17), prostate, oesophageal, colon and bladder cancer. Most patients (16/21) had received prior chemotherapy; none radiotherapy. Median number of daily perifosine administrations was 31 (range 24-53). Mean radiation dose (BED(10)) was 59.8 Gy (range 50.7-87.5 Gy in 13-28 fractions).

RESULTS

Major drug-related toxicities according to CTC criteria were nausea in 57%, fatigue in 48%, vomiting in 38%, diarrhoea in 38% and anorexia in 19%. No bone marrow toxicity was observed. DLT (nausea/vomiting) was encountered in two of five patients at the 200mg/day dose level. Dose-dependent steady-state plasma levels were reached after 1 week. Major radiotherapy-related acute toxicity consisted of dysphagia in 38% and pneumonitis in 29%.

CONCLUSION

Perifosine can be safely combined with fractionated radiotherapy. A dosage of 150 mg/day, to be started at least 1 week prior to radiotherapy, is recommended for phase II evaluation.

Increased cytotoxicity of ionizing radiation in combination with membrane-targeted apoptosis modulators involves downregulation of protein kinase B/Akt-mediated survival-signaling

BACKGROUND AND PURPOSE

The membrane-targeted apoptosis modulators erucylphosphocholine (ErPC) and erucylphosphohomocholine (ErPC3) induce apoptosis in highly apoptosis resistant malignant glioma cell lines and enhance radiation-induced cell death and eradication of clonogenic tumor cells in vitro. Aim of the present study was to elucidate molecular mechanisms of combined action.

MATERIALS AND METHODS

Induction of apoptosis was evaluated by determination of nuclear morphology (fluorescence microscopy), alteration of mitochondrial function and caspase-activation (flow cytometry, Western blot). Activity of protein kinase B (PKB/Akt) and key downstream effectors involved in apoptosis regulation was verified by Western blot analysis using activation-specific antibodies.

RESULTS

Increased cytotoxicity of the combination was linked to a more efficient activation of the intrinsic apoptosis pathway with increased damage of the mitochondria and caspase-activation. Moreover, activity of the survival kinase PKB/Akt was downregulated upon treatment with ErPC/ErPC3 alone or in combination with ionizing radiation. Inhibition of PKB/Akt was associated with decreased phosphorylation and thus activation of the pro-apoptotic Bcl-2 protein Bad as well as dephosphorylation of the transcription factor FOXO3A (FKHRL1) that may be responsible for the observed increased expression of the pro-apoptotic Bcl-2 protein Bim.

CONCLUSIONS

Our data suggest a role for inhibition of PKB/Akt-mediated anti-apoptotic signaling in increased efficacy of the combination.

Overcoming the radioresistance of prostate cancer cells with a novel Bcl-2 inhibitor

Bcl-2 overexpression is an important mechanism underlying the aggressive behavior of prostate cancer cells and their resistance to radio- or chemotherapy. HA14-1, a recently discovered organic Bcl-2 inhibitor, potently induces apoptosis in various human cancer cells. Sequential exposure of radioresistant LNCaP (wild-type (wt) p53), LNCaP/Bcl-2 (wt p53) and PC3 (mutant p53) prostate cancer cells to a minimally cytotoxic concentration of 10 microM HA14-1 for 1 h followed by 1-6 Gy gamma radiation, resulted in a highly synergistic (combination index <1.0) induction of cell death as determined by an apoptosis assay at 72 h, and a clonogenicity assay at 12 days, after the initial treatment. The reverse treatment sequence did not cause a synergistic induction of cell death. When compared to individual treatments, cell death induced by the combined treatment was associated with dramatically increased reactive oxygen species (ROS) generation, c-Jun N-terminal kinase (JNK) activation, Bcl-2 phosphorylation, cytochrome c release, caspase-3 activation and DNA fragmentation. Exposure to either 200 microg/ml of the antioxidant alpha-tocopherol or 10 microM JNK inhibitor SP600125 before the combined treatment resulted in decreased activation of JNK and caspase-3 as well as decreased DNA fragmentation. However, treatment with the pancaspase inhibitor carbobenzoxyl-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone before the combined treatment inhibited apoptosis without affecting JNK activation, and this inhibitory effect was enhanced in the presence of alpha-tocopherol or SP600125. Taken together, our results indicate that HA14-1 potently sensitizes radioresistant LNCaP and PC3 cells to gamma radiation, regardless of the status of p53. ROS and JNK are important early signals that trigger both caspase-dependent and -independent cell death pathways and contribute to the apoptotic synergy induced by the combined treatments.

Radiosensitization of squamous cell carcinoma by the alkylphospholipid perifosine in cell culture and xenografts

PURPOSE

Combined modality treatment has improved outcome in various solid tumors. Besides classic anticancer drugs, a new generation of biological response modifiers has emerged that increases the efficacy of radiation. Here, we have investigated whether perifosine, an orally applicable, membrane-targeted alkylphospholipid, enhances the antitumor effect of radiation in vitro and in vivo.

EXPERIMENTAL DESIGN

Several long-term and short-term in vitro assays (clonogenic survival, sulforhodamine B cytotoxicity, apoptosis, and cell cycle analysis) were used to assess the cytotoxic effect of perifosine in combination with radiation. In vivo, the response of human KB squamous cell carcinoma xenografts was measured after treatment with perifosine, irradiation, and the combination. Radiolabeled perifosine was used to determine drug disposition in tumor and normal tissues. At various intervals after treatment, tumor specimens were collected to document histopathologic changes.

RESULTS

In vitro, perifosine reduced clonogenic survival, enhanced apoptosis, and increased cell cycle arrest after radiation. In vivo, radiation and perifosine alone induced a dose-dependent tumor growth delay. When combining multiple perifosine administrations with single or split doses of radiation, complete and sustained tumor regression was observed. Histopathologic analysis of tumor specimens revealed a prominent apoptotic response after combined treatment with radiation and perifosine. Radiation-enhanced tumor response was observed at clinically relevant plasma perifosine concentrations and accumulating drug disposition of >100 microg/g in tumor tissue.

CONCLUSIONS

Perifosine enhances radiation-induced cytotoxicity, as evidenced by reduced clonogenic survival and increased apoptosis induction in vitro and by complete tumor regression in vivo. These data provide strong support for further development of this combination in clinical studies.

Tumor-specific apoptotic gene targeting overcomes radiation resistance in esophageal adenocarcinoma

PURPOSE

To overcome radiation resistance in esophageal adenocarcinoma by tumor-specific apoptotic gene targeting using tumor necrosis factor-related apoptosis-inducing ligand (TRAIL).

METHODS AND MATERIALS

Adenoviral vector Ad/TRAIL-F/RGD with a tumor-specific human telomerase reverse transcription promoter was used to transfer TRAIL gene to human esophageal adenocarcinoma and normal human lung fibroblastic cells (NHLF). Activation of apoptosis was analyzed by Western blot, fluorescent activated cell sorting, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate labeling (TUNEL) assay. A human esophageal adenocarcinoma mouse model was treated with intratumoral injections of Ad/TRAIL-F/RGD plus local radiotherapy.

RESULTS

The combination of Ad/TRAIL-F/RGD and radiotherapy increased the cell-killing effect in all esophageal adenocarcinoma cell lines but not in NHLF cells. This combination also significantly reduced clonogenic formation (p < 0.05) and increased sub-G1 deoxyribonucleic acid accumulation in cancer cells (p < 0.05). Activation of apoptosis by Ad/TRAIL-F/RGD plus radiotherapy was demonstrated by activation of caspase-9, caspase-8, and caspase-3 and cleaved poly (adenosine diphosphate-ribose) polymerase in vitro and TUNEL assay in vivo. Combined Ad/TRAIL-F/RGD and radiotherapy dramatically inhibited tumor growth and prolonged mean survival in the esophageal adenocarcinoma model to 31.6 days from 16.7 days for radiotherapy alone and 21.5 days for Ad/TRAIL-F/RGD alone (p < 0.05).

CONCLUSIONS

The combination of tumor-specific TRAIL gene targeting and radiotherapy enhances the effect of suppressing esophageal adenocarcinoma growth and prolonging survival.

Combined treatment of colorectal tumours with agonistic TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 and radiotherapy: enhanced effects in vitro and dose-dependent growth delay in vivo

We and others have demonstrated already that TRAIL (TNF-related apoptosis-inducing ligand) is a very promising candidate for molecular targeted anticancer therapy, especially when combined with ionizing radiation or other DNA-damaging agents. Agonist monoclonal antibodies that activate and are specific for the death signaling TRAIL receptors are an alternative method to stimulate the programmed cell death pathway. Phase 1 clinical trials have subsequently been conducted and shown a very good tolerability of these antibodies. In order to assess the efficacy of TRAIL receptor stimulation to induce cell death by this alternate method, we studied the combination of the agonistic-TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 with radiation in vitro and in vivo. Induction of apoptosis after combined treatment with TRAIL receptor antibodies HGS-ETR1 and/or HGS-ETR2 (0.01, 0.1, 1.0 mg/ml) and irradiation with 2, 5 or 10 Gy was determined by fluorescence microscopy and Western blot analysis of caspase-8 and PARP. The colorectal tumour cell lines Colo 205, HCT 116 and HCT-15 were used for in vitro experiments. Growth delay experiments were performed with combined treatment with fractionated irradiation (days 1-5 and 3 Gy single dose/day) and the receptor antibodies (intraperitonially, three different concentrations, application on days 1, 4 and 8) on Colo 205 xenograft-bearing NMRI (nu/nu) nude mice. HGS-ETR1 and HGS-ETR2 induced apoptotic cell death in a dose-dependent fashion and significantly increased cell death in combination with irradiation in vitro when compared to either irradiation or antibody treatment alone. The efficacy of the combined treatment seems to be at least partially Bax-dependent. Similar to the results from cell culture experiments, in vivo experiments demonstrated a dose-dependent delay in tumour growth after combined treatment. In vivo, in the Colo205 xenograft model, HGS-ETR2 revealed a higher activity than HGS-ETR1. This is the first study to demonstrate significant efficacy of combined treatment with the monoclonal agonistic TRAIL receptor antibodies HGS-ETR1 and HGS-ETR2 and ionising radiation in in vitro and in vivo models. We postulate that HGS-ETR1 and HGS-ETR2 will be very promising new agents in the field of molecular targeted multi-modality anticancer therapy.

TRAIL activates acid sphingomyelinase via a redox mechanism and releases ceramide to trigger apoptosis

We have previously shown that activation of the acid sphingomyelinase (ASM), the release of ceramide and the formation of ceramide-enriched membrane domains are central for the induction of apoptosis by CD95. Here, we demonstrate that tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and CD95 activate the ASM via a redox mechanism resulting in release of ceramide and formation of ceramide-enriched membrane platforms. Ceramide-enriched membrane platforms serve to cluster DR5 upon stimulation. Antioxidants prevent TRAIL-mediated stimulation of ASM, the release of ceramide, the formation of ceramide-enriched membrane platforms and the induction of apoptosis by TRAIL. Further, ASM-deficient splenocytes fail to cluster DR5 in ceramide-enriched membrane domains upon TRAIL stimulation and resist TRAIL-induced apoptosis, events that were restored by addition of natural C(16)-ceramide. A dose-response analysis indicates that ceramide-enriched membrane platforms greatly sensitized tumor cells to TRAIL-induced apoptosis. Our data indicate that ceramide-enriched membrane platforms are required for the signaling of TRAIL-DR5 complexes under physiological conditions.

Combination of celecoxib with percutaneous radiotherapy in patients with localised prostate cancer - a phase I study

BACKGROUND

Current approaches for the improvement of bNED for prostate cancer patients treated with radiotherapy mainly focus on dose escalation. However molecularly targeted approaches may also turn out to be of value. In this regard cyclooxygenase (COX)-2 inhibitors have been shown to exert some anti-tumour activities in human prostate cancer in vivo and in vitro. Although in vitro data indicated that the combination of COX-2 inhibition and radiation was not associated with an increased toxicity, we performed a phase I trial using high dose celecoxib together with percutaneous radiation therapy.

METHODS

In order to rule out any increases of more than 20% incidence for a given side effect level 22 patients were included in the trial. Celecoxib was given 400 mg twice daily with onset of the radiation treatment. Risk adapted radiation doses were between 70 and 74 Gy standard fractionation. RTOG based gastrointestinal (GI) and genitourinary (GU) acute toxicity scoring was performed weekly during radiation therapy, at six weeks after therapy and three month after completing radiation treatment.

RESULTS

Generally no major increase in the level and incidence of side effects potentially caused by the combined treatment was observed. In two cases a generalised skin rash occurred which immediately resolved upon discontinuation of the drug. No grade 3 and 4 toxicity was seen. Maximal GI toxicity grade 1 and 2 was observed in 85% and 10%, respectively. In terms of GU toxicity 80% of the patients experienced a grade 1 toxicity and 10 % had grade 2 symptoms.

CONCLUSION

The combination of irradiation to the prostate with concurrent high dose celecoxib was not associated with an increased level of side effects.

The membrane targeted apoptosis modulators erucylphosphocholine and erucylphosphohomocholine increase the radiation response of human glioblastoma cell lines in vitro

Background

Alkylphosphocholines constitute a novel class of antineoplastic synthetic phospholipid derivatives that induce apoptosis of human tumor cell lines by targeting cellular membranes. We could recently show that the first intravenously applicable alkylphosphocholine erucylphosphocholine (ErPC) is a potent inducer of apoptosis in highly resistant human astrocytoma/glioblastoma cell lines in vitro. ErPC was shown to cross the blood brain barrier upon repeated intravenous injections in rats and thus constitutes a promising candidate for glioblastoma therapy. Aim of the present study was to analyze putative beneficial effects of ErPC and its clinically more advanced derivative erucylphosphohomocholine (erucyl-N, N, N-trimethylpropanolaminphosphate, ErPC3, Erufosine™ on radiation-induced apoptosis and eradication of clonogenic tumor cells in human astrocytoma/glioblastoma cell lines in vitro.

Results

While all cell lines showed high intrinsic resistance against radiation-induced apoptosis as determined by fluorescence microscopy, treatment with ErPC and ErPC3 strongly increased sensitivity of the cells to radiation-induced cell death (apoptosis and necrosis). T98G cells were most responsive to the combined treatment revealing highly synergistic effects while A172 showed mostly additive to synergistic effects, and U87MG cells sub-additive, additive or synergistic effects, depending on the respective radiation-dose, drug-concentration and treatment time. Combined treatment enhanced therapy-induced damage of the mitochondria and caspase-activation. Importantly, combined treatment also increased radiation-induced eradication of clonogenic T98G cells as determined by standard colony formation assays.

Conclusion

Our observations make the combined treatment with ionizing radiation and the membrane targeted apoptosis modulators ErPC and ErPC3 a promising approach for the treatment of patients suffering from malignant glioma. The use of this innovative treatment concept in an in vivo xenograft setting is under current investigation.

Tumor radiosensitizers--current status of development of various approaches: report of an International Atomic Energy Agency meeting

PURPOSE

The International Atomic Energy Agency (IAEA) held a Technical Meeting of Consultants to (1) discuss a selection of relatively new agents, not those well-established in clinical practice, that operated through a variety of mechanisms to sensitize tumors to radiation and (2) to compare and contrast their tumor efficacy, normal tissue toxicity, and status of development regarding clinical application. The aim was to advise the IAEA as to which developing agent or class of agents would be worth promoting further, by supporting additional laboratory research or clinical trials, with the eventual goal of improving cancer control rates using radiotherapy, in developing countries in particular.

RESULTS

The agents under discussion included a wide, but not complete, range of different types of drugs, and antibodies that interfered with molecules in cell signaling pathways. These were contrasted with new molecular antisense and gene therapy strategies. All the drugs discussed have previously been shown to act as tumor cell radiosensitizers or to kill hypoxic cells present in tumors.

CONCLUSION

Specific recommendations were made for more preclinical studies with certain of the agents and for clinical trials that would be suitable for industrialized countries, as well as trials that were considered more appropriate for developing countries.

The fate of irradiated tumor cells

Radiotherapy remains a key component of modern multimodal anticancer treatment approaches. Although most clinically relevant improvements in radiation oncology are based on optimized radiation technology, it now becomes obvious that biology-based approaches will further boost the efficacy of modern radiation oncology. Of relevance to this is the question of the ultimate fate of an irradiated cell and the mechanistic basis of the induced cell death or inactivation observed. Research bearing on this question is reported in this issue of Oncogene by Wendt et al. (2005), who show that the levels of p21CIP/WAF1 play a key role in determining whether an irradiated tumour cell is arrested in the G2 phase of the cell cycle, rather than apoptosing. The demonstration that caffeine treatment can abrogate this G2 arrest, and that the cells go on to die, has implications for overcoming treatment resistance imposed by radiation-induced upregulation of p21CIP/WAF1.

Why "radiation oncology"

Radiotherapy continues to be a major treatment for solid tumours and is a cornerstone of modern oncology. The term 'radiation oncology' describes the integration of radiation therapy into the complexity of multi-modal therapy. Over the last ten years the crucial role of radiation therapy as part of multi-modality protocols in cancer care has been documented in numerous Phase III trials. Advances in treatment technology as well as the underlying biology of tumour resistance mechanisms will further strengthen the role of radiation oncology. The scientific role of radiation oncology is reflected by the increase in the number of papers related to radiation oncology in resources like Medline. In order to reflect the growing scientific importance of radiation oncology, radiation physics and radiation biology, we have initiated Radiation Oncology as the first open access journal in the field. Open access allows for a rapid and transparent publication process together with an unequalled opportunity to reach the widest reader spectrum possible.

Sensitization for gamma-irradiation-induced apoptosis by second mitochondria-derived activator of caspase

Resistance to current treatment regimens, such as radiation therapy, remains a major concern in oncology and may be caused by defects in apoptosis programs. Because inhibitor of apoptosis proteins (IAPs), which are expressed at high levels in many tumors, block apoptosis at the core of the apoptotic machinery by inhibiting caspases, therapeutic modulation of IAPs could target a key control point in resistance. Here, we report for the first time that full-length or mature second mitochondria-derived activator of caspase (Smac), an inhibitor of IAPs, significantly enhanced gamma-irradiation-induced apoptosis and reduced clonogenic survival in neuroblastoma, glioblastoma, or pancreatic carcinoma cells. Notably, Smac had no effect on DNA damage/DNA repair, activation of nuclear factor-kappaB, up-regulation of p53 and p21 proteins, or cell cycle arrest following gamma-irradiation, indicating that Smac did not alter the initial damage and/or cellular stress response. Smac enhanced activation of caspase-2, caspase-3, caspase-8, and caspase-9, loss of mitochondrial membrane potential, and cytochrome c release on gamma-irradiation. Inhibition of caspases also blocked gamma-irradiation-induced mitochondrial perturbations, indicating that Smac facilitated caspase activation, which in turn triggered a mitochondrial amplification loop. Interestingly, mitochondrial perturbations were completely blocked by the broad-range caspase inhibitor N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone or the relatively selective caspase-2 inhibitor N-benzyloxycarbonyl-Val-Asp-Val-Ala-Asp-fluoromethylketone, whereas caspase-8 or caspase-3 inhibitors only inhibited the increased drop of mitochondrial membrane potential provided by Smac, suggesting that caspase-2 was acting upstream of mitochondria after gamma-irradiation. In conclusion, our findings provide evidence that targeting IAPs (e.g., by Smac agonists) is a promising strategy to enhance radiosensitivity in human cancers.

Proapoptotic activity of Ukrain is based on Chelidonium majus L. alkaloids and mediated via a mitochondrial death pathway

BACKGROUND

The anticancer drug Ukrain (NSC-631570) which has been specified by the manufacturer as semisynthetic derivative of the Chelidonium majus L. alkaloid chelidonine and the alkylans thiotepa was reported to exert selective cytotoxic effects on human tumour cell lines in vitro. Few clinical trials suggest beneficial effects in the treatment of human cancer. Aim of the present study was to elucidate the importance of apoptosis induction for the antineoplastic activity of Ukrain, to define the molecular mechanism of its cytotoxic effects and to identify its active constituents by mass spectrometry.

METHODS

Apoptosis induction was analysed in a Jurkat T-lymphoma cell model by fluorescence microscopy (chromatin condensation and nuclear fragmentation), flow cytometry (cellular shrinkage, depolarisation of the mitochondrial membrane potential, caspase-activation) and Western blot analysis (caspase-activation). Composition of Ukrain was analysed by mass spectrometry and LC-MS coupling.

RESULTS

Ukrain turned out to be a potent inducer of apoptosis. Mechanistic analyses revealed that Ukrain induced depolarisation of the mitochondrial membrane potential and activation of caspases. Lack of caspase-8, expression of cFLIP-L and resistance to death receptor ligand-induced apoptosis failed to inhibit Ukrain-induced apoptosis while lack of FADD caused a delay but not abrogation of Ukrain-induced apoptosis pointing to a death receptor independent signalling pathway. In contrast, the broad spectrum caspase-inhibitor zVAD-fmk blocked Ukrain-induced cell death. Moreover, over-expression of Bcl-2 or Bcl-xL and expression of dominant negative caspase-9 partially reduced Ukrain-induced apoptosis pointing to Bcl-2 controlled mitochondrial signalling events. However, mass spectrometric analysis of Ukrain failed to detect the suggested trimeric chelidonine thiophosphortriamide or putative dimeric or monomeric chelidonine thiophosphortriamide intermediates from chemical synthesis. Instead, the Chelidonium majus L. alkaloids chelidonine, sanguinarine, chelerythrine, protopine and allocryptopine were identified as major components of Ukrain. Apart from sanguinarine and chelerythrine, chelidonine turned out to be a potent inducer of apoptosis triggering cell death at concentrations of 0.001 mM, while protopine and allocryptopine were less effective. Similar to Ukrain, apoptosis signalling of chelidonine involved Bcl-2 controlled mitochondrial alterations and caspase-activation.

CONCLUSION

The potent proapoptotic effects of Ukrain are not due to the suggested "Ukrain-molecule" but to the cytotoxic efficacy of Chelidonium majus L. alkaloids including chelidonine.

Radiotherapy sensitization by tumor-specific TRAIL gene targeting improves survival of mice bearing human non-small cell lung cancer

PURPOSE

To sensitize non-small cell lung cancer (NSCLC) to radiotherapy by tumor-specific delivery of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) gene.

EXPERIMENTAL DESIGN

The TRAIL was delivered to human NSCLC cell lines and normal human bronchial epithelial cells by the replication-defective adenoviral vector Ad/TRAIL-F/RGD using a tumor-specific human telomerase reverse transcriptase promoter. Cancer growth was studied using 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide inner salt and clonogenic assays. Activation of the apoptosis pathway was analyzed in a Western blot and sub-G(1) DNA accumulation. A xenograft mouse lung cancer model was treated by intratumoral injections of Ad/TRAIL-F/RGD and local radiotherapy; the other groups received one of these treatments alone or a control agent. Apoptosis and TRAIL expression in tumors were also analyzed.

RESULTS

Ad/TRAIL-F/RGD specifically targets human NSCLC cells without significant effect in normal human bronchial epithelial cells. The combination of Ad/TRAIL-F/RGD and radiotherapy significantly improved cell-killing effect in all NSCLC cell lines tested (P < 0.05). Expression of TRAIL showed a dose-dependent relationship with Ad/TRAIL-F/RGD, and radiation seemed to increase TRAIL expression. Activation of the apoptosis by TRAIL and radiation was shown by activation of caspase-9, caspase-8, caspase-3, and poly(ADP-ribose) polymerase and increased DNA sub-G(1) accumulation. The combination of TRAIL and radiotherapy significantly increased apoptosis in vivo, inhibited tumor growth, and prolonged mean survival in mice bearing human NSCLC to 43.7 days compared with 23.7 days (TRAIL only) and 16.5 days (radiotherapy only; P < 0.05).

CONCLUSIONS

The combination of Ad/TRAIL-F/RGD and radiotherapy significantly improved therapeutic efficacy in suppressing NSCLC tumor growth and prolonging survival. Ad/TRAIL-F/RGD may improve the therapeutic ratio of radiotherapy in NSCLC.

Bcl-2 mediated inhibition of erucylphosphocholine-induced apoptosis depends on its subcellular localisation

The synthetic phospholipid derivative erucylphosphocholine (ErPC) is a potent inducer of apoptosis in human tumor cell lines. This membrane-targeted drug induces apoptosis independently from death receptor signaling through a mitochondrial pathway that is inhibited by over-expression of Bcl-2. Within the cell, Bcl-2 resides in membranes of mitochondria, endoplasmic reticulum (ER) and the nucleus. However, the importance of its subcellular localisation in distinct organelles for protection against apoptosis is not completely understood. To investigate the impact of Bcl-2 localised at defined subcellular compartments on its protective effects against ErPC-induced apoptosis, Bcl-2 expression was directed to the outer membrane of the mitochondria or the ER of Jurkat T Lymphoma cells, using Bcl-2 mutants with modified membrane anchors. The mitochondrial insertion sequence of ActA directed Bcl-2 to the mitochondria (Bcl-2/MT), the ER-specific sequence of cytochrome b5 to the ER (Bcl-2/ER). Additionally, Jurkat cells expressing wild-type Bcl-2 (Bcl-2/WT) or a transmembrane domain-lacking mutant (Bcl-2/DeltaTM) were employed. While restricted expression of Bcl-2 either at membranes of the mitochondria or the ER strongly interfered with ErPC-induced mitochondrial damage and apoptosis, cytosolic Bcl-2/DeltaTM exhibited only reduced protection. Thus, membrane localisation of Bcl-2 is a prerequisite for substantial protection against ErPC-induced apoptosis. For efficient long-term inhibition of ErPC-induced apoptosis Bcl-2 had to be present in the membranes of both compartments, the ER and the mitochondria. The finding that ER-targeted Bcl-2 interferes with ErPC-induced mitochondrial damage points to an involvement of the ER in apoptosis signaling upstream of the mitochondria and to a crosstalk between both compartments.

Tumor and normal tissue pharmacokinetics of perifosine, an oral anti-cancer alkylphospholipid

Clinical use of anti-cancer alkylphospholipids is limited by gastrointestinal toxicity. However, new interest has emerged since it was shown that these drugs enhance the cytotoxic effect of conventional chemotherapy and radiotherapy in preclinical models. The aim of this study was to characterize the pharmacokinetic profile of perifosine, an oral analog of alkylphosphocholine (APC), and to compare in vitro drug uptake with in vivo drug accumulation in three human-derived squamous cell carcinomas (A431, HNXOE and KB). In vitro, KB cells showed a remarkably high uptake and sensitivity for perifosine compared with A431 and HNXOE cells. In vivo, perifosine reached a clinically relevant plasma concentration in mice after a single oral dose of 40 mg/kg. Perifosine was not metabolized and displayed slow elimination, with a terminal half-life of 137 (+/- 20) hours and an apparent volume of distribution of 11.3 l/kg. Comparable tumor accumulation was observed for A431 and HNXOE tumors, whereas perifosine uptake by KB xenografts was substantially higher. Tissue distribution occurred throughout the whole body reaching high perifosine levels in the gastro-intestinal tract, while heart and brain tissue contained relatively low levels. Based on its stability and relatively high tumor uptake in vivo, perifosine is an attractive candidate for further evaluation, e.g. as radiosensitizer.

Radiosensitivity of human colon cancer cell enhanced by immunoliposomal docetaxel

AIM: To enhance the radiosensitivity of human colon cancer cells by docetaxel.

METHODS: Immunoliposomal docetaxel was prepared by coupling monoclonal antibody against carcinoembryonic antigen to cyanuric chloride at the PEG terminus of liposome. LoVo adenocarcinoma cell line was treated with immunoliposomal docetaxel or/and irradiation. MTT colorimetric assay was used to estimate cytotoxicity of immunoliposomal docetaxel and radiotoxicity. Cell cycle redistribution and apoptosis were determined with flow cytometry. Survivin expression in LoVo cells was verified by immunohistochemistry. D801 morphologic analysis system was used to semi-quantify immunohistochemical staining of survivin.

RESULTS: Cytotoxicity was induced by immunoliposomal docetaxel alone in a dose-dependent manner. Immunoli-posomal docetaxel yielded a cytotoxicity effect at a low dose of 2 nmol/L. With a single dose irradiation, the relative surviving fraction of LoVo cells showed a dose-dependent response, but there were no significant changes as radiation delivered from 4 to 8 Gy. Compared with liposomal docetaxel or single dose irradiation, strongly radiopotentiating effects of immunoliposomal docetaxel on LoVo cells were observed. A low dose of immunoliposomal docetaxel could yield sufficient radiosensitivity. Immunoliposomal docetaxel were achieved both specificity of the conjugated antibody and drug radiosensitization. Combined with radiation, immunoliposomal docetaxel significantly increased the percentage of G₂/M cells and induced apoptosis, but significantly decreased the percentage of cells in G₂/G₁ and S phase by comparison with liposomal docetaxel. Immunohistochemical analysis showed that the brown stained survivin was mainly in cytoplasm of LoVo cells. Semi-quantitative analysis of the survivin immunostaining showed that the expression of survivin in LoVo cells under irradiation with immunoliposomal docetaxel was significantly decreased.

CONCLUSION: Immunoliposomal docetaxel is strongly effective for target radiosensitation in LoVo colon carcinoma cells, and may offer the potential to improve local radiotherapy.

[Basics of molecular diagnostics and therapy of malignant tumors]

Recent insights in disease pathogenesis and mechanisms of resistance to therapy of malignant tumors provide a rational basis for the development of novel therapeutic strategies that target genetic defects and deregulated signaling events in malignant tumors. In contrast to conventional therapeutics, small molecule inhibitors or monoclonal antibodies allow for a far more selective, targeted therapy of tumors that carry a corresponding target structure or gene expression profile. Molecular therapeutics therefore necessitate clinical deployment of genetic diagnostics for the identification of those patients who have a chance to benefit from these novel targeted therapies.

In vivo imaging of apoptosis by 99mTc-Annexin V scintigraphy: visual analysis in relation to treatment response

BACKGROUND AND PURPOSE

Anticancer therapy induces apoptosis in a dose- and time-dependent fashion. (99m)Tc-Hynic-rh-Annexin V scintigraphy (TAVS) enables non-invasive in vivo imaging of treatment-induced apoptosis. We identified the visual patterns of (99m)Tc-Hynic-rh-Annexin V tumour uptake and related these to treatment response.

PATIENTS AND METHODS

Thirty-three patients with malignant lymphoma (n=26), leukaemia (n=1) NSCLC (n=5), H&NSCC (n=1), scheduled for radiotherapy (n=27), platinum-based chemotherapy (n=5) or concurrent chemoradiation (n=1), underwent TAVS before and early after the start of treatment. Planar and SPECT images were visually examined to assess changes in tumour (99m)Tc-Hynic-rh-Annexin V uptake. Twenty-nine patients were eligible for further analysis. Annexin V uptake before (U(baseline)) and early after (U(post)) the start of treatment was graded using a four-step scale: 0, absent; 1, weak; 2, moderate and 3, intense. The difference between these values (Delta U) was calculated and correlated to tumour response after therapy (Spearman rank correlation test).

RESULTS

Weak to moderate U(baseline) was detected in 13/15 patients with a complete response and U(post) was markedly increased in all these cases (Delta U range 1-3). Partial response (n=7) was associated with weak to moderate U(baseline) and a moderately increased U(post) (Delta U range 1-2). In patients with stable disease (n=5), U(baseline) was predominantly weak, without considerable changes in uptake after the start of treatment (Delta U range 0-1). Finally, in case of progressive disease (n=2), either no tumour uptake or a decrease in U(post) was detected (Delta U=-1). A statistically significant correlation was found between changes in (99m)Tc-Hynic-rh-Annexin V tumour uptake and clinical response (correlation coefficient=0.62; P<0.001).

CONCLUSIONS

Complete or partial tumour response was associated with a marked increase of (99m)Tc Hynic-rh-Annexin V accumulation early during treatment compared to baseline values. In case of stable or progressive disease, pretreatment scans demonstrated predominantly low (99m)Tc Hynic-rh-Annexin V tumour uptake and no significant increase early after treatment. These results indicate that TAVS might be useful as a predictive test for treatment response.