Recent advances in the use of radiosensitizing nucleosides

Vacuum ultraviolet spectroscopy of pyrimidine derivatives: the effect of halogenation

As a prototypical molecule in the important class of halopyrimidines, 2-chloropyrimidine has been the subject of numerous spectroscopic studies. However, its absorption spectrum under vacuum ultraviolet (VUV) radiation has not yet been reported. Here, we close this gap by presenting high-resolution VUV photoabsorption cross-sections in the 3.7-10.8 eV range. Based on time-dependent density functional theory (TDDFT) calculations performed within the nuclear ensemble approach, we are able to characterize the main features of the measured spectrum. By comparing the present results for 2-chloropyrimidine with those of 2-bromopyrimidine and pyrimidine, we find that the effect of the halogen atom increases remarkably with the photon energy. The two lowest-lying absorption bands are overall similar for the three molecules, apart from some differences in the vibrational progressions in band I (3.7-4.6 eV) and minor energy shifts in band II (4.6-5.7 eV). Larger shifts appear in band III (5.7-6.7 eV), especially when comparing pyrimidine with the two halogenated species. The three molecules absorb more strongly in the region of band IV (6.7-8.2 eV), where the bands look qualitatively different because the mixing of excited configurations is strongly dependent on the species. At higher energies (8.2-10.8 eV) the three spectra no longer resemble each other. An important finding of this study is the very satisfactory comparison between experiment and theory, as the combination of TDDFT calculations with the nuclear ensemble approach yields cross-sections much closer to experiments than the simpler vertical approximation, in shape and magnitude, and across the whole spectral range surveyed here.

177Lu-DOTATATE Plus Capecitabine Versus 177Lu-DOTATATE Alone in Patients with Advanced Grade 1/2 Gastroenteropancreatic Neuroendocrine Tumors (LuCAP): A Randomized, Phase 2 Trial

177Lu-DOTATATE has emerged as a viable treatment strategy for advanced well-differentiated grade 1/2 gastroenteropancreatic neuroendocrine tumors (GEP-NETs). Few retrospective studies have shown concomitant 177Lu-DOTATATE with radiosensitizing low-dose capecitabine to be effective in advanced NETs. However, this has not been validated in prospective randomized-controlled trials. Methods: In this investigator-initiated, parallel-group, open-label, phase 2 trial, patients with grade 1/2 GEP-NETs, having progressive somatostatin receptor-positive, locally advanced, or metastatic disease on 68Ga-DOTANOC PET/CT, were randomly assigned in a 1:1 ratio to 177Lu-DOTATATE plus capecitabine (experimental arm) or 177Lu-DOTATATE only (control arm). 177Lu-DOTATATE was administered at approximately 7.4 GBq/cycle intravenously, for up to 4 cycles, at 8 wk intervals, whereas capecitabine was given at 1,250 mg/m2/d orally from day 0 to day 14 of each cycle of 177Lu-DOTATATE. The primary endpoint was the objective response rate. Secondary endpoints included the disease control rate, progression-free survival, overall survival, and adverse events. Results: Seventy-two patients (median age, 53 y; range, 18-79 y) were enrolled. The objective response rate was 33.3% (95% CI, 18.6-50.9%) in the experimental arm versus 30.6% (95% CI, 16.4-48.1%) in the control arm (P = 0.800). The disease control rate was 88.9% (95% CI, 73.9-96.9%) and 91.7% (95% CI, 77.5-98.2%) in the experimental and control arms, respectively (P = 1.000). The estimated median progression-free survival in the experimental arm was 29 mo (95% CI, 22-29 mo) versus 31 mo (95% CI, 29-32 mo) in the control arm (P = 0.401). The median overall survival was not reached in either arm (P = 0.876). Overall, adverse events of at least grade 3 were noted in 7 patients in the experimental arm versus 6 patients in the control arm (P = 0.759). Conclusion: Based on the results of this trial, the addition of low-dose capecitabine to 177Lu-DOTATATE in advanced grade 1/2 GEP-NETs did not lead to superior radiographic responses. Further studies are needed to evaluate its potential role in high-grade NETs.

An Analysis of the Radiosensitiser Applications in the Biomedical Field

BACKGROUND

Various types of radiosensitisers have been introduced from the past until the present day for applications in the biomedical field. However, there is a lack of understanding and comparison between the various parameters introduced in addition to a lack of consensus among researchers on the optimal radiosensitiser for applications in the biomedical field.

OBJECTIVE

This review aimed to investigate the usage of radiosensitisers in the biomedical field, determine their important parameters, and suggest radiosensitisers with potential among the analysed radiosensitisers.

RESULTS AND CONCLUSION

This review has discussed several parameters for radiosensitisers, including median lethal dose, cell survival, tumour size, cell viability, Dose Enhancement Factor (DEF), Reactive Oxygen Species (ROS) concentration, radiosensitiser production complexity, radiosensitiser administration technique, and radiosensitiser toxicity. General trends regarding the development of radiosensitisers, including the types, effectiveness, and their production complexity, have also been discussed within this review article.

Combined Effects of Annexin A5 Overexpression, 5-Fluorouracil Treatment, and Irradiation on Cell Viability of Caski Cervical Cancer Cell Line

Cervical cancer is the fourth leading cause of cancer deaths in women globally. Combining gene therapy with chemo- and radiotherapy may improve cervical cancer treatment outcomes. This study evaluated the effects of Annexin A5(ANXA5) overexpression alongside 5-fluorouracil (5-FU) and irradiation on the viability of CaSki cervical squamous cell carcinoma (SCC) cells. pAdenoVator-CMV-ANXA5-IRES-GFP-plasmid and mock plasmid were transfected into CaSki cells using calcium-phosphate. Seventy-two hours post-transfection, GFP expression was quantified by fluorescence microscopy and flow cytometry to evaluate transfection efficiency. ANXA5 overexpression was confirmed via qPCR. Twenty-four hours post-transfection, cells received a single dose of 8 Gy and were treated with 1 and 2 µg/ml of 5-FU (IC50 = 2.783 µg/ml). Cell viability, apoptosis, cell cycle stage, and Bcl-2 and Bax gene expression were assessed via MTT, annexin V/7-AAD, PI staining, and qPCR assays, respectively. ANXA5 was overexpressed 31.5-fold compared to control (p < 0.0001). MTT assays showed ANXA5 overexpression dose-dependently reduced CaSki cell viability (p < 0.001). IC50 of 5-FU was reduced from 2.783 μg/mL to 1.794 μg/mL when combined with ANXA5 overexpression. Additive effects on cell death were observed for ANXA5 plus 5-FU or irradiation versus ANXA5 alone. Apoptosis assays indicated combinatorial treatment increased CaSki cell apoptosis over ANXA5 alone. Cell cycle analysis revealed ANXA5 arrested cell cycle at G1/S phases; the percentage of cells in the S phase further rose with combination treatment. Finally, combination therapy significantly decreased Bcl-2 expression and increased Bax versus control (p < 0.001). Altogether, ANXA5 overexpression alongside 5-FU and irradiation may improve cervical squamous cell carcinoma (SCC) treatment efficacy. Further, in vivo investigations are warranted to confirm these in vitro results.

Microbiome in radiotherapy: an emerging approach to enhance treatment efficacy and reduce tissue injury

Radiotherapy is a widely used cancer treatment that utilizes powerful radiation to destroy cancer cells and shrink tumors. While radiation can be beneficial, it can also harm the healthy tissues surrounding the tumor. Recent research indicates that the microbiota, the collection of microorganisms in our body, may play a role in influencing the effectiveness and side effects of radiation therapy. Studies have shown that specific species of bacteria living in the stomach can influence the immune system's response to radiation, potentially increasing the effectiveness of treatment. Additionally, the microbiota may contribute to adverse effects like radiation-induced diarrhea. A potential strategy to enhance radiotherapy outcomes and capitalize on the microbiome involves using probiotics. Probiotics are living microorganisms that offer health benefits when consumed in sufficient quantities. Several studies have indicated that probiotics have the potential to alter the composition of the gut microbiota, resulting in an enhanced immune response to radiation therapy and consequently improving the efficacy of the treatment. It is important to note that radiation can disrupt the natural balance of gut bacteria, resulting in increased intestinal permeability and inflammatory conditions. These disruptions can lead to adverse effects such as diarrhea and damage to the intestinal lining. The emerging field of radiotherapy microbiome research offers a promising avenue for optimizing cancer treatment outcomes. This paper aims to provide an overview of the human microbiome and its role in augmenting radiation effectiveness while minimizing damage.

Nucleoside Analogs Radiosensitize G0 Cells by Activating DNA End Resection and Alternative End-Joining

Alternative end-joining (alt-EJ) is a DNA end resection-dependent, error-prone pathway utilized by vertebrate cells to repair DNA double-strand breaks (DSBs), but its engagement is linked to chromosomal translocations and genomic instability. Here, we report that when proliferating cells are exposed to ionizing radiation, treatment with nucleoside analogs (NAs) causes strong radiosensitization by increasing engagement of alt-EJ, while at the same time suppressing homologous recombination (HR) in S- and G2phase cells. This NA-mediated pathway shift may reflect a passive compensatory engagement of alt-EJ following HR suppression that is specific for S- and G2-phase cells, and/or the direct activation of alt-EJ throughout the cell cycle. To distinguish between these possibilities, we utilize here a cell culture model that exploits genetic and cell cycle-dependent inactivation of DSB repair pathways, to exclusively study alt-EJ and its modulation by NAs in murine and human cell lines. To this end, we allow LIG4-/--deficient cells to accumulate in G1/G0 phase by transfer to serum-deprived media and obtain cells deficient in c-NHEJ owing to the genetic LIG4 knockout, deficient in HR owing to the absence of S- or G2-phase cells, and compromised in their ability to carry out alt-EJ owing to their accumulation in G0. We find that in these cells irradiation and treatment with the NA, β-arabinofuranosyladenine (araA), and to a lesser degree with other NAs, promptly activates suppressed alt-EJ that now functions at levels approximating those of c-NHEJ in wild-type cells. Results at high dose (20 Gy) generated using pulsed-field gel electrophoresis (PFGE) are corroborated by results at low dose (1 Gy) generated by scoring 53BP1 foci. Strikingly, araA treatment activates a normally undetectable DNA-end-resection at DSBs, which requires ATR activity, but proceeds unimpeded after CtIP knockdown. Treatment with araA increases the formation of chromosomal aberrations and enhances radiation-induced cell killing. The results support direct stimulation of resection by NAs and alt-EJ as a mechanism of their documented radiosensitizing potential. We propose that this stimulation also occurs in repair-proficient cells and that it occurs throughout the cell cycle. It may therefore be harnessed to develop protocols combining NAs with radiation to treat human cancer.

Adjuvant Therapy in Resected Nonmetastatic Stage II-IV Gallbladder Cancer: A Generalized Propensity Score Analysis

BACKGROUND

The clinical benefits and efficacies of adjuvant therapies for gallbladder cancer (GBC) have not been verified due to insufficient clinical evidence.

METHODS

Patients with resected nonmetastatic stage II-IV GBC were selected from the Surveillance, Epidemiology, and End Results database and distributed into nonchemotherapy and chemoradiotherapy (NCRT), chemotherapy (CT), and chemoradiotherapy (CRT) groups. Generalized propensity score and inverse probability of treatment weighting (IPTW) were used to reduce the imbalances between groups.

RESULTS

A total of 2,689 patients were enrolled, among whom 1,193 (44.4%) were classified as stage II, 1,371 (51.0%) as stage III, and 125 (4.6%) as stage IV GBC. A total of 1,703, 444, and 542 patients were placed in the NCRT, CT, and CRT groups, respectively. After the IPTW, there were no significant differences in overall survival (OS) between the 3 treatment groups (p > 0.05) in stage II GBC patients. In patients with stage III-IV GBC, the CT group exhibited a superior OS compared to the NCRT group (p < 0.001). In addition, the CRT group exhibited a superior OS compared to the CT (p < 0.001) and NCRT (p < 0.001) groups. For patients with stage III-IV tumors, a nomogram was constructed to predict the survival benefits of adjuvant therapies.

CONCLUSION

Patients with stage II GBC may not benefit from adjuvant therapy, while patients with stage III-IV GBC were shown to benefit from chemotherapy and chemoradiotherapy. Furthermore, chemoradiotherapy exhibited a superior OS. Nevertheless, the results need to be explained in the context of retrospective studies.

Pre-treatment with Bifidobacterium infantis and its specific antibodies enhance targeted radiosensitization in a murine model for lung cancer

PURPOSE

The hypoxic microenvironments of solid tumours are complex and reduce the susceptibility of cancer cells to chemo- and radiotherapy. Conventional radiosensitisers have poor specificity, unsatisfactory therapeutic effects, and significant side effects. Anaerobic bacteria colonise and destroy hypoxic areas of the tumour and consequently enhance the effects of radiation.

METHODS

In this study, we treated a Lewis lung carcinoma transplant mouse model with Bifidobacterium infantis (Bi) combined with its specific monoclonal antibody (mAb) and radiotherapy (RT) to investigate its ability to radiosensitise the tumour. The tumour metabolism and hypoxia in the tumour tissue were monitored by micro-¹⁸F-FDG and ¹⁸F-FMISO PET/CT imaging. Immunohistochemistry was used to detect phosphorylated histone (γ-H2AX), proliferation (Ki-67), platelet endothelial cell adhesion molecules (CD31), tumour necrosis factor-α (TNF-α), hypoxia-inducible factor-1α (HIF-1α), and glucose transporter 1 (Glut-1) levels.

RESULTS

Tumour growth was slowed and survival time was markedly prolonged in mice subjected to the combination of B. infantis, specific antibody, and radiotherapy. Levels of HIF-1α, Glut-1, Ki-67, and CD31 expression, as well as uptake of FDG and FMISO, were the lowest in the combination-treated mice. In contrast, γ-H2AX and TNF-α expression levels were elevated and hypoxia in tumour tissue was reduced compared with controls.

CONCLUSION

In conclusion, our data indicated that the curative effect of radiotherapy for lung cancer was enhanced by pre-treating mice with a combination of B. infantis and its specific monoclonal antibody.

Targeting Cullin-RING E3 Ligases for Radiosensitization: From NEDDylation Inhibition to PROTACs

As a dynamic regulator for short-lived protein degradation and turnover, the ubiquitin-proteasome system (UPS) plays important roles in various biological processes, including response to cellular stress, regulation of cell cycle progression, and carcinogenesis. Over the past decade, research on targeting the cullin-RING (really interesting new gene) E3 ligases (CRLs) in the UPS has gained great momentum with the entry of late-phase clinical trials of its novel inhibitors MLN4924 (pevonedistat) and TAS4464. Several preclinical studies have demonstrated the efficacy of MLN4924 as a radiosensitizer, mainly due to its unique cytotoxic properties, including induction of DNA damage response, cell cycle checkpoints dysregulation, and inhibition of NF-κB and mTOR pathways. Recently, the PROteolysis TArgeting Chimeras (PROTACs) technology was developed to recruit the target proteins for CRL-mediated polyubiquitination, overcoming the resistance that develops inevitably with traditional targeted therapies. First-in-class cell-permeable PROTACs against critical radioresistance conferring proteins, including the epidermal growth factor receptor (EGFR), androgen receptor (AR) and estrogen receptor (ER), cyclin-dependent kinases (CDKs), MAP kinase kinase 1 (MEK1), and MEK2, have emerged in the past 5 years. In this review article, we will summarize the most important research findings of targeting CRLs for radiosensitization.

Modifications at the C(5) position of pyrimidine nucleosides

This review summarizes the state of knowledge on the chemical methods of C(5)-modifications of uridine and cytidine derivatives and may serve as a useful tool for synthetic chemists to choose an appropriate reaction protocol. The synthesis of 5-substituted uracil derivatives is gaining an increasing interest because of their possible applications in medicine and pharmacy. Modifications at the C(5) position of pyrimidine nucleosides can enhance their biostability, bioavailability or(and) biological activity. Among the C(5)-modified nucleosides, 5-halopyrimidines exhibit anticancer, antiviral, radio- and photosensitizing properties. Besides 5-halo-substituted derivatives, there are other examples of nucleosides with confirmed biological activity containing a C–C bond at the C(5) position in the pyrimidine ring. In recent decades, scientists have achieved great progress in the field of cross-coupling reactions. Among them, nickel-catalyzed processes provide a broad spectrum of synthetic methods that are based on less toxic and cheaper starting materials. This review summarizes the synthetic approaches based on the coupling or halogenation reactions, which enable 5-substituted pyrimidine nucleosides to be obtained. Moreover, the importance of the systems considered for medicine and pharmacy is briefly discussed.

The bibliography includes 197 references.

Exposure of Breast and Lung Cancer Cells to a Novel Estrone Analog Prior to Radiation Enhances Bcl-2-Mediated Cell Death

Following exposure of cells to gamma-radiation, a cascade of intracellular consequences may be observed in a semitemporal manner. This includes deoxyribonucleic acid (DNA) damage and reactive oxygen species (ROS) accumulation initially, with consequent signaling for DNA repair and facilitative regulation of the cell cycle. Failure to rectify the damage or ROS levels leads to induction of senescence or apoptosis. 2-Ethyl-3-O-sulfamoyl-estra-1,3,5(10),15-tetraen-17-ol (ESE-15-ol), a 2-methoxyestradiole analog designed in silico for superior pharmacokinetics, was investigated for its potential to enhance apoptotic signaling and decrease the long-term survival of cells exposed to radiation. Sequential early intracellular effects within radiation-treated MCF-7 breast- and A549 lung cancer cells pre-exposed to low-dose ESE-15-ol were investigated using various flow cytometric protocols, spectrophotometry, and microscopy. Long-term cellular survival and proliferation was examined using clonogenic studies, which demonstrated a significant decrease in the presensitized cells. Combination-treated cells exhibited increased superoxide formation, and decreased Bcl-2 expression and -phosphorylation. Induction of apoptosis and elevation of the sub-G₁ phase was evident in the pre-exposed MCF-7 cells, although only minimally in the A549 cells at 48-h. These results indicate that low-dose ESE-15-ol may increase tumor response to radiation. Future studies will investigate the effect of ESE-15-ol pre-exposure on radiation-induced DNA damage and repair mechanisms.

Lymph node yield after rectal resection in patients treated with neoadjuvant radiation for rectal cancer: A systematic review and meta-analysis

BACKGROUND

The lymph node status represents a major prognostic factor in colorectal cancer. However, it was demonstrated that neoadjuvant chemoradiotherapy (CRT) decreases the numbers of lymph nodes in the specimen. Several studies describe less than 12 lymph nodes in the resected specimen of rectal cancer patients after neoadjuvant radiation. This meta-analysis quantifies the influence of neoadjuvant CRT or radiotherapy (RT) only on the lymph node yield in rectal cancer patients.

METHODS

We performed a systematic review and searched PubMed, EMBASE and the Cochrane Library without any language restriction from 1st of January 1980 until 31st March 2015. Two reviewers examined all publications independently and extracted the relevant data if the study assessed lymph node counts or positive lymph node yields of patients who received neoadjuvant treatment compared with patients who did not receive neoadjuvant treatment. Meta-analyses were conducted to quantify the mean difference in lymph node yield.

RESULTS

A total of 34 articles (including 37 datasets) were included in the meta-analyses. Neoadjuvant CRT resulted in a mean reduction of 3.9 lymph nodes (95% confidence interval [CI] 3.7-4.1) and an average reduction in harvested positive lymph nodes of 0.7 (95% CI 0.2-1.2) compared with patients who received no neoadjuvant therapy. Individuals who received neoadjuvant RT had, in average, 2.1 lymph node less (95% CI 1.7-2.5) resected compared with their counterparts who received no neoadjuvant treatment.

CONCLUSIONS

Neoadjuvant CRT or RT only in rectal cancer patients leads to a decrease in lymph node harvest of approximately four and two lymph nodes, respectively. We therefore stress the importance of intensifying all efforts from involved subspecialities (i.e. surgeons and pathologists) to reach the benchmark harvest of 12 resected lymph nodes according to current guidelines.

Electrophilic 5-Substituted Uracils as Potential Radiosensitizers: A Density Functional Theory Study

Although 5-bromo-2'-deoxyuridine (5BrdU) possesses significant radiosensitizing power in vitro, clinical studies do not confirm any advantages of radiotherapy employing 5BrdU. This situation calls for a continuous search for efficient radiosensitizers. Using the proposed mechanism of radiosensitization by 5BrdU, we propose a series of 5-substituted uracils, XYU, that should undergo efficient dissociative electron attachment. The DFT-calculated thermodynamic and kinetic data concerning the XYU degradations induced by electron addition suggests that some of the scrutinized derivatives have much better characteristics than 5BrdU itself. Synthesis of these promising candidates for radiosensitizers, followed by studies of their radiosensitizing properties in DNA context, and ultimately in cancer cells, are further steps to confirm their potential applicability in anticancer treatment.

Radiotherapy and gemcitabine-docetaxel chemotherapy in children and adolescents with unresectable recurrent or refractory osteosarcoma

OBJECTIVE

Few reports have described the treatment outcome of osteosarcoma using radiotherapy. We evaluated the efficacy of radiotherapy and gemcitabine and docetaxel chemotherapy for patients with unresectable recurrent or refractory osteosarcoma.

METHODS

Data from six patients (five male, one female) who received radiotherapy and gemcitabine and docetaxel chemotherapy at the Korea Cancer Center Hospital were retrospectively reviewed. Tumor response was evaluated according to metabolic changes using (18)F-fluorodeoxy-D-glucose-positron emission tomography.

RESULTS

The median age of the patients was 15.0 years (range, 14.0-15.8 years). Two patients had single bone lesions, and four had multiple metastatic bone lesions. Patients received a median 3.5 courses of gemcitabine and docetaxel chemotherapy (range, 2-6 courses). The median dose of radiotherapy was 50.0 Gy (range, 46-84 Gy). There were two complete metabolic responses and one partial metabolic response. The objective response rate was 50.0% (3/6). Responses were maintained for 4.6, 6.1 and 13.7 months, respectively. Patients were followed up for a median of 5.8 months (range, 2.7-84.6 months), and the median progression-free survival after this treatment was 3.6 months (range, 1.1-13.7 months). At the time of analysis, two patients were alive, one was lost to follow-up and three had died.

CONCLUSION

Radiotherapy with gemcitabine and docetaxel chemotherapy showed some improvement in cases of refractory tumors or multiple bone metastases. Further studies are needed to investigate the efficacy of newer radiotherapy modalities, as well as to identify new radiosensitizing chemotherapy regimens.

Chemoradiotherapy for patients with recurrent lymph-node metastasis or local recurrence of gastric cancer after curative gastrectomy

OBJECTIVES

Whether chemoradiotherapy (CRT) is clinically beneficial for the management of postoperative recurrence of advanced gastric cancer remains unclear. We retrospectively studied treatment outcomes in patients who had unresectable localized recurrence after surgery for advanced gastric cancer and evaluated the safety and efficacy of CRT.

METHODS

The study group comprised 21 patients who received concurrent CRT for unresectable localized recurrence after undergoing R0 resection for stage II/III advanced gastric cancer. Localized recurrence was defined as a few or limited recurrent lesions.

RESULTS

The recurrence pattern was anastomotic recurrence in 7 patients, abdominal lymph-node recurrence in 12, and anastomotic recurrence plus abdominal lymph-node recurrence in 2. The median total dose of radiotherapy was 48.6 Gy (range 39.6-56.0), and the CRT completion rate was 100 % (21 of 21 patients). CRT-related grade 3 or higher toxicity comprised neutropenia in 33.3 % of patients and anorexia in 9.5 %. The response rate was 61.9 % (complete response 38.1 %, partial response 23.8 %). The median overall survival was 35.0 months.

CONCLUSIONS

We conclude that CRT may become one treatment strategy for the management of unresectable localized recurrence after curative resection of advanced gastric cancer.

Radiosensitization of gliomas by intracellular generation of 5-fluorouracil potentiates prodrug activator gene therapy with a retroviral replicating vector

A tumor-selective non-lytic retroviral replicating vector (RRV), Toca 511, and an extended-release formulation of 5-fluorocytosine (5-FC), Toca FC, are currently being evaluated in clinical trials in patients with recurrent high-grade glioma (NCT01156584, NCT01470794 and NCT01985256). Tumor-selective propagation of this RRV enables highly efficient transduction of glioma cells with cytosine deaminase (CD), which serves as a prodrug activator for conversion of the anti-fungal prodrug 5-FC to the anti-cancer drug 5-fluorouracil (5-FU) directly within the infected cells. We investigated whether, in addition to its direct cytotoxic effects, 5-FU generated intracellularly by RRV-mediated CD/5-FC prodrug activator gene therapy could also act as a radiosensitizing agent. Efficient transduction by RRV and expression of CD were confirmed in the highly aggressive, radioresistant human glioblastoma cell line U87EGFRvIII and its parental cell line U87MG (U87). RRV-transduced cells showed significant radiosensitization even after transient exposure to 5-FC. This was confirmed both in vitro by a clonogenic colony survival assay and in vivo by bioluminescence imaging analysis. These results provide a convincing rationale for development of tumor-targeted radiosensitization strategies utilizing the tumor-selective replicative capability of RRV, and incorporation of radiation therapy into future clinical trials evaluating Toca 511 and Toca FC in brain tumor patients.

Targeted therapy against EGFR and VEGFR using ZD6474 enhances the therapeutic potential of UV-B phototherapy in breast cancer cells

Background

The hypoxic environment of tumor region stimulated the up regulation of growth factors responsible for angiogenesis and tumor proliferation. Thus, targeting the tumor vasculature along with the proliferation by dual tyrosine kinase inhibitor may be the efficient way of treating advanced breast cancers, which can be further enhanced by combining with radiotherapy. However, the effectiveness of radiotherapy may be severely compromised by toxicities and tumor resistance due to radiation-induced adaptive response contributing to recurrence and metastases of breast cancer. The rational of using ZD6474 is to evaluate the feasibility and efficacy of combined VEGFR2 and EGFR targeting with concurrent targeted and localized UV-B phototherapy in vitro breast cancer cells with the anticipation to cure skin lesions infiltrated with breast cancer cells.

Materials and methods

Breast cancer cells were exposed to UV-B and ZD6474 and the cell viability, apoptosis, invasion and motility studies were conducted for the combinatorial effect. Graphs and statistical analyses were performed using Graph Pad Prism 5.0.

Results

ZD6474 and UV-B decreased cell viability in breast cancers in combinatorial manner without affecting the normal human mammary epithelial cells. ZD6474 inhibited cyclin E expression and induced p53 expression when combined with UV-B. It activated stress induced mitochondrial pathway by inducing translocation of bax and cytochrome-c. The combination of ZD6474 with UV-B vs. either agent alone also more potently down-regulated the anti-apoptotic bcl-2 protein, up-regulated pro-apoptotic signaling events involving expression of bax, activation of caspase-3 and caspase-7 proteins, and induced poly (ADP-ribose) polymerase resulting in apoptosis. ZD6474 combined with UV-B inhibited invasion of breast cancer cells in vitro as compared to either single agent, indicating a potential involvement of pro-angiogenic growth factors in regulating the altered expression and reorganization of cytoskeletal proteins in combinatorial treated breast cancer cells. Involvement of combination therapy in reducing the expression of matrix metalloprotease was also observed.

Conclusions

Collectively, our studies indicate that incorporating an anti-EGFR plus VEGFR strategy (ZD6474) with phototherapy (UV-B), an alternative approach to the ongoing conventional radiotherapy for the treatment of infiltrating metastatic breast cancer cells in the skin and for locally recurrence breast cancer than either approach alone.

Re-evaluation of cellular radiosensitization by 5-fluorouracil: high-dose, pulsed administration is effective and preferable to conventional low-dose, chronic administration

PURPOSE

It is widely believed that the anticancer drug 5- fluorouracil (5-FU) must be administered chronically and in low doses to maximize radiosensitization during chemoradiotherapy. The rationale is based upon cell experiments that assumed identical mechanisms of 5-FU action between low-dose chronic (LDC) and high-dose pulsed (HDP) exposures. Here we challenge the paradigm and demonstrate the effectiveness of HDP 5-FU as a radiosensitizer and the wide range of dose/time schedules that can be used to synergize with radiation as compared to the relatively restrictive protocols prescribed for current LDC administrations.

MATERIALS AND METHODS

Clonogenic survival of human glioblastoma and colon cancer cell lines, U87MG-VIII and HCT-116, respectively, was used to assess temporal and dose effects of 5-FU on radiosensitivity and in split-dose experiments to characterize changes in sublethal damage repair.

RESULTS

We show that HDP 5-FU administration does indeed radiosensitize both the highly radioresistant U87MG-VIII and HCT-116. Additionally, we show that this radiosensitization lasts for at least 24 h if cells are pre-irradiated with 2 Gy immediately after HDP 5-FU exposure as a result of a decrease in sublethal damage repair capacity for subsequent irradiations, suggesting the ideal combination of 5-FU bolus injection with fractionation radiotherapy schemes.

CONCLUSIONS

5-FU bolus administration protocols combined with radiation would not only help improve treatment outcomes and reduce development of 5-FU resistance, but it would greatly benefit patients by shortening clinical stays and lowering overall therapeutic costs.

Chapter seven--Cancer treatment with gene therapy and radiation therapy

Radiation therapy methods have evolved remarkably in recent years which have resulted in more effective local tumor control with negligible toxicity of surrounding normal tissues. However, local recurrence and distant metastasis often occur following radiation therapy mostly due to the development of radioresistance through the deregulation of the cell cycle, apoptosis, and inhibition of DNA damage repair mechanisms. Over the last decade, extensive progress in radiotherapy and gene therapy combinatorial approaches has been achieved to overcome resistance of tumor cells to radiation. In this review, we summarize the results from experimental cancer therapy studies on the combination of radiation therapy and gene therapy.

Motexafin gadolinium: a promising radiation sensitizer in brain metastasis

INTRODUCTION

Motexafin gadolinium is a radiation sensitizer that is in the class of drugs known as texaphyrins. Though this drug is currently not FDA approved in the management of brain tumors, several prospective studies have been done showing promise with this agent, which this review highlights.

AREAS COVERED

This paper provides a clinical context by reviewing the background of radiosensitizers, followed by a review of the preclinical discovery of motexafin gadolinium and its clinical testing. We also highlight its most promising applications and comment on the reasons for the observed clinical outcomes.

EXPERT OPINION

Motexafin gadolinium is a novel radiosensitizer with clearly documented efficacy, particularly in patients with brain metastases. If this agent had been tested upfront in patients diagnosed with brain metastases from NSCLC who had not been delayed by the administration of systemic chemotherapy, it may have become part of the standard of care in this setting. Continued investigations using this agent are under way and remain promising.

Inhibition of tumor growth and metastasis by a combination of Escherichia coli-mediated cytolytic therapy and radiotherapy

We have reported that Escherichia coli K-12 colonizes hypoxic and necrotic tumor regions after intravenous injection into tumor-bearing mice. In this study, we established a novel strategy for cancer therapy using engineered bacteria to enhance the therapeutic effects of radiation. E. coli strain K-12 was engineered to produce cytolysin A (ClyA), and its effects on tumor growth in primary and metastatic tumor models were evaluated. A single treatment with E. coli-expressing ClyA significantly decreased tumor growth rates initially (9 days after treatment); however, the tumors tended to grow thereafter. With only radiotherapy (RT; 21 Gy), the tumor growth rates were retarded, but not the tumor sizes. A combination of therapy with E. coli-expressing ClyA and radiation [a total of 5 x 10(7) colony-forming units (CFU) and 21 Gy] resulted in significant tumor shrinkage and even complete disappearance of tumors in mice with tumors derived from murine CT26 colon cancer. Furthermore, treatment with E. coli-expressing ClyA markedly suppressed metastatic tumor growth and prolonged the survival time in mice. The results described here indicate that therapy with engineered E. coli could significantly improve the results of RT, and could exert a striking inhibitory effect on the development of lung metastasis.

Motexafin gadolinium: a novel radiosensitizer for brain tumors

For a variety of reasons, the management of brain tumors, both primary and metastatic, remains a considerable challenge. As most systemic therapies do not cross the BBB at therapeutic doses, radiation and surgery have played primary roles in the management of these diseases. Despite significant advances in surgical techniques and radiation delivery, outcomes for most adult brain tumors continue to be poor. In an effort to enhance the effects of radiation in the brain, a variety of radiation sensitizers, including motexafin gadolinium, have been investigated. In the following manuscript, we summarize motexafin gadolinium and its role in brain tumors.

Radiosensitizing effects of temozolomide observed in vivo only in a subset of O6-methylguanine-DNA methyltransferase methylated glioblastoma multiforme xenografts

PURPOSE

Concurrent temozolomide (TMZ) and radiation therapy (RT) followed by adjuvant TMZ is standard treatment for patients with glioblastoma multiforme (GBM), although the relative contribution of concurrent versus adjuvant TMZ is unknown. In this study, the efficacy of TMZ/RT was tested with a panel of 20 primary GBM xenografts.

METHODS AND MATERIALS

Mice with intracranial xenografts were treated with TMZ, RT, TMZ/RT, or placebo. Survival ratio for a given treatment/line was defined as the ratio of median survival for treatment vs. placebo.

RESULTS

The median survival ratio was significantly higher for O6-methylguanine-DNA methyltransferase (MGMT) methylated tumors versus unmethylated tumors following treatment with TMZ (median survival ratio, 3.6 vs. 1.5, respectively; p = 0.008) or TMZ/RT (5.7 vs. 2.3, respectively; p = 0.001) but not RT alone (1.7 vs. 1.6; p = 0.47). In an analysis of variance, MGMT methylation status and p53 mutation status were significantly associated with treatment response. When we analyzed the additional survival benefit conferred specifically by combined therapy, only a subset (5 of 11) of MGMT methylated tumors derived substantial additional benefit from combined therapy, while none of the MGMT unmethylated tumors did. Consistent with a true radiosensitizing effect of TMZ, sequential treatment in which RT (week 1) was followed by TMZ (week 2) proved significantly less effective than TMZ followed by RT or concurrent TMZ/RT (survival ratios of 4.0, 9.6 and 12.9, respectively; p < 0.0001).

CONCLUSIONS

Concurrent treatment with TMZ and RT provides significant survival benefit only in a subset of MGMT methylated tumors and provides superior antitumor activity relative to sequential administration of RT and TMZ.

Myelopathy After Radiation Therapy and Chemotherapy with Capecitabine and Gemcitabine

This article describes a woman with metastatic upper gastrointestinal cancer who developed thoracic myelopathy unexpectedly after standard dosage and fractionation radiotherapy. She also was receiving capecitabine and gemcitabine concomitantly. There are few reported cases of chemotherapy potentiation of spinal cord radiation toxicity. These agents are known radiosensitizers, making it likely that they contributed to this adverse outcome. As these agents are increasingly incorporated into clinical trials of combined therapy, caution will be necessary in both trial design and clinical management.

Concurrent capecitabine and whole-brain radiotherapy for treatment of brain metastases in breast cancer patients

Preclinical data have demonstrated that ionizing radiation acts synergistically with capecitabine. This report retrospectively assessed the use of capecitabine concurrently with whole-brain radiotherapy (WBRT) in patients with brain metastases from breast cancer. From January 2003 to March 2005, five breast cancer patients with brain metastases were referred for WBRT with concurrent capecitabine. Median age was 44 years (range: 38-53). The median dose of capecitabine was 1,000 mg/m(2) twice daily for 14 days (day1-14). Treatment cycles were repeated every 21 days, concurrently with WBRT (30 Gy, 3 Gy per fraction, 5 days per week). Median survival after starting WBRT plus capecitabine was 6.5 months (range 1-34 months). One patient achieved a complete response. Two patients achieved partial response, including one with local control lasting until most recent follow-up. One patient had stable disease. The remaining patient was not assessable for response because of early death. Most commonly reported adverse events were nausea (n = 2) and headache (n = 2), always grade 1. Other toxicities were grade 3 hand/foot syndrome (n = 1), moderate anemia requiring transfusion and dose reduction of capecitabine (n = 1), and grade 1 mucositis (n = 1). Although promising, these preliminary data warrant further assessment of capecitabine-based chemoradiation in brain metastases from breast cancer and need to be further validated in the setting of a clinical trial.

Molecular chemotherapy of pancreatic cancer using novel mutant bacterial cytosine deaminase gene

The combination of molecular chemotherapy with radiation therapy has the potential to become a powerful approach for treatment of pancreatic cancer. We have developed an adenoviral vector (AdbCD-D314A) encoding a mutant bacterial cytosine deaminase (bCD) gene, which converts the prodrug 5-fluorocytosine (5-FC) into the active drug 5-fluorouracil. The aim of this study was to investigate AdbCD-D314A/5-FC-mediated cytotoxicity in vitro and therapeutic efficacy in vivo alone and in combination with radiation against human pancreatic cancer cells and xenografts. AdbCD-D314A/5-FC-mediated cytotoxicity alone and in combination with radiation was analyzed using crystal violet inclusion and clonogenic survival assays. CD enzyme activity was determined by measuring conversion of [3H]5-FC to [3H]5-fluorouracil after adenoviral infection of pancreatic cancer cells in vitro and pancreatic tumor xenografts by TLC. S.c. pancreatic tumor xenografts were used to evaluate the therapeutic efficacy of AdbCD-D314A/5-FC molecular chemotherapy in combination with radiation therapy. AdbCD-D314A infection resulted in increased 5-FC-mediated pancreatic cancer cell killing that correlated with significantly enhanced CD enzyme activity compared with AdbCDwt encoding wild-type of bCD. Animal studies showed significant inhibition of growth of human pancreatic tumors treated with AdbCD-D314A/5-FC in comparison with AdbCDwt/5-FC. Also, a significantly greater inhibition of growth of Panc2.03 and MIA PaCA-2 tumor xenografts was produced by the combination of AdbCD-D314A/5-FC with radiation compared with either agent alone. The results indicate that the combination of AdbCD-D314A/5-FC molecular chemotherapy with radiation therapy significantly enhanced cytotoxicity of pancreatic cancer cells in vitro and increased therapeutic efficacy against human pancreatic tumor xenografts.

Clofarabine acts as radiosensitizer in vitro and in vivo by interfering with DNA damage response

PURPOSE

Combination treatment with radiotherapy and chemotherapy has emerged as the dominant form of cancer adjuvant regimens in recent years. Clofarabine, a newly approved drug for pediatric leukemia, is a second-generation purine nucleoside analogue that can block DNA synthesis and inhibit DNA repair. Therefore, we hypothesized that clofarabine could work synergistically with radiotherapy to increase the tumor cell response.

METHODS AND MATERIALS

The effects of clofarabine on radiosensitivity have been established in several tumor cell lines in vitro and in vivo using colony-forming assays and tumor xenografts. The effect of clofarabine on the DNA damage response was also studied in vitro by measuring gamma-H2AX focus formation.

RESULTS

Clonogenic survival was significantly reduced in irradiated cells treated with clofarabine, demonstrating the strong radiosensitizing effect of clofarabine. Furthermore, clofarabine displayed a radiosensitizing effect that was greater than gemcitabine or 5-fluorouracil. We also found that low doses of clofarabine can prolong the presence of radiation-induced gamma-H2AX nuclear focus formation, and high doses of clofarabine can induce DNA double-strand breaks, suggesting that clofarabine can interfere with DNA damage response pathways. In addition, clofarabine-induced radiosensitization was also established in vivo using a colorectal cancer model, DLD-1, in athymic nude mice. When combined with fractionated radiotherapy, a moderate dose of clofarabine led to a significant increase in tumor growth inhibition.

CONCLUSION

Clofarabine acts as a powerful radiosensitizer both in vitro and in vivo by interfering with the DNA damage response.

Impact of preoperative chemoradiotherapy on survival in patients with resectable pancreatic cancer

AIM: To explore whether preoperative chemoradiation therapy improves survival of patients with pancreatic cancer undergoing resectional surgery.

METHODS: Forty-seven patients with a malignant pancreatic tumor localized in the head or uncinate process of the pancreas underwent radical pancreatico-duodenectomy. Twenty-two received chemoradiation therapy (gemcitabine and radiation dose 50.4 Gy) before surgery (CRR) and 25 patients underwent surgery only (RO). The study was non-randomised. Patients were identified from a prospective database.

RESULTS: The median survival time was 30.2 mo in the CRR group and 35.9 mo in the RO group. No statistically significant differences were found in subclasses according to lymph node involvement, TNM stages, tumor size, or perineural invasion. The one, three and five year survival rates were 81%, 33% and 33%, respectively, in the CRR group and 72%, 47% and 23%, respectively, in the RO group. In ductal adenocarcinoma, the median survival time was 27 mo in the CRR group and 20 mo in the RO group. No statistically significant differences were found in the above subclasses. The one, three and five year survival rates were 79%, 21% and 21%, respectively, in the CRR group and 64%, 50% and 14%, respectively, in the RO group. The overall hospital mortality rate was 2%. The morbidity rate was 45% in the CRR group and 32% (NS) in the RO group.

CONCLUSION: Major multicenter randomized studies are needed to conclusively assess the impact of neoadjuvant treatment in the management of pancreatic cancer.

Treatment combining X-irradiation and a ribonucleoside anticancer drug, TAS106, effectively suppresses the growth of tumor cells transplanted in mice

PURPOSE

To examine the in vivo antitumor efficacy of X-irradiation combined with administration of a ribonucleoside anticancer drug, 1-(3-C-ethynyl-beta-D-ribo-pentofuranosyl)cytosine (TAS106, ECyd), to tumor cell-transplanted mice.

METHODS AND MATERIALS

Colon26 murine rectum adenocarcinoma cells and MKN45 human gastric adenocarcinoma cells were inoculated into the footpad in BALB/c mice and severe combined immunodeficient mice, respectively. They were treated with a relatively low dose of X-irradiation (2 Gy) and low amounts of TAS106 (0.1 mg/kg and 0.5 mg/kg). The tumor growth was monitored by measuring the tumor volume from Day 5 to Day 16 for Colon26 and from Day 7 to Day 20 for MKN45. Histologic analyses for proliferative and apoptotic cells in the tumors were performed using Ki-67 immunohistochemical and terminal deoxynucleotidyl transferase-mediated nick end labeling staining. The expression of survivin, a key molecule related to tumor survival, was assessed by quantitative polymerase chain reaction and immunohistochemical analysis.

RESULTS

When X-irradiation and TAS106 treatment were combined, significant inhibition of tumor growth was observed in both types of tumors compared with mice treated with X-irradiation or TAS106 alone. Marked inhibition of tumor growth was observed in half of the mice that received the combined treatment three times at 2-day intervals. Parallel to these phenomena, the suppression of survivin expression and appearance of Ki-67-negative and apoptotic cells were observed.

CONCLUSIONS

X-irradiation and TAS106 effectively suppress tumor growth in mice. The inhibition of survivin expression by TAS106 is thought to mainly contribute to the suppression of the tumor growth.

Chemical radiosensitizers for use in radiotherapy

Radiosensitizers are intended to enhance tumour cell killing while having much less effect on normal tissues. Some drugs target different physiological characteristics of the tumour, particularly hypoxia associated with radioresistance. Oxygen is the definitive hypoxic cell radiosensitizer, the large differential radiosensitivity of oxic vs hypoxic cells being an attractive factor. The combination of nicotinamide to reduce acute hypoxia with normobaric carbogen breathing is showing clinical promise. 'Electron-affinic' chemicals that react with DNA free radicals have the potential for universal activity to combat hypoxia-associated radioresistance; a nitroimidazole, nimorazole, is clinically effective at tolerable doses. Hypoxia-specific cytotoxins, such as tirapazamine, are valuable adjuncts to radiotherapy. Nitric oxide is a potent hypoxic cell radiosensitizer; variations in endogenous levels might have prognostic significance, and routes to deliver nitric oxide specifically to tumours are being developed. In principle, many drugs can be delivered selectively to hypoxic tumours using either reductase enzymes or radiation-produced free radicals to activate drug release from electron-affinic prodrugs. A redox-active agent based on a gadolinium chelate is being evaluated clinically. Pyrimidines substituted with bromine or iodine are incorporated into DNA and enhance free radical damage; fluoropyrimidines act by different mechanisms. A wide variety of drugs that influence the nature or repair of DNA damage are being evaluated in conjunction with radiation; it is often difficult to define the mechanisms underlying chemoradiation regimens. Drugs being evaluated include topoisomerase inhibitors (e.g. camptothecin, topotecan), and the hypoxia-activated anthraquinone AQ4N; alkylating agents include temozolomide. Drugs involved in DNA repair pathways being investigated include the potent poly(ADP ribose)polymerase inhibitor, AG14,361. Proteins involved in cell signalling, such as the Ras family, are attractive targets linked to radioresistance, as are epidermal growth factor receptors and linked kinases (drugs including vandetanib [ZD6,474], cetuximab and gefitinib), and cyclooxygenase-2 (celecoxib). The suppression of radioprotective thiols seems to offer more potential with alkylating agents than with radiotherapy, although it remains a strategy worthy of exploration.

Lipodermatosclerosis as a form of vascular compromise-associated radiation recall dermatitis: case report and a review of literature

Lipodermatosclerosis (LDS) is a prototypic ischemic dermopathy that is most commonly associated with venous insufficiency. There have been no prior reports describing LDS as a form of radiation recall dermatitis (RRD). We present a case of a 47-year-old female affected by squamous cell carcinoma of the anus who underwent irradiation and subsequent chemotherapy with 5-fluorouracil and cisplatin. She then developed tender, erythematous, indurated plaques on skin of the buttocks, corresponding closely to one of the previous radiotherapy fields. As histopathological studies were compatible with LDS and the skin eruption coincided with drug intake 3 months after radiotherapy, the diagnosis of RRD with LDS features was rendered. This is the first case providing evidence of the causative role of 5-fluorouracil and cisplatin in potentially inducing RRD.

The concurrent chemoradiation paradigm—general principles

During the past 20 years, the advent of neoadjuvant, primary, and adjuvant concurrent chemoradiotherapy has improved cancer care dramatically. Significant contributions have been made by technological improvements in radiotherapy, as well as by the introduction of novel chemotherapy agents and dosing schedules. This article will review the rationale for the use of concurrent chemoradiotherapy for treating malignancies. The molecular basis and mechanisms of action of combining classic cytotoxic agents (e.g. platinum-containing drugs, taxanes, etc.) and novel agents (e.g. tirapazamine, EGFR inhibitors and other targeted agents) with radiotherapy will be examined. This article is part one of two articles. In the subsequent article, the general principles outlined here will be applied to head and neck cancer, in which the impact of concurrent chemoradiotherapy is particularly evident.

Base excision repair of both uracil and oxidatively damaged bases contribute to thymidine deprivation-induced radiosensitization

PURPOSE

Increased cellular sensitivity to ionizing radiation due to thymidine depletion is the basis of radiosensitization with fluoropyrimidine and methotrexate. The mechanism responsible for cytotoxicity has not been fully elucidated but appears to involve both the introduction of uracil into, and its removal from, DNA. The role of base excision repair of uracil and oxidatively damaged bases in creating the increased radiosensitization during thymidine depletion is examined.

METHODS AND MATERIALS

Isogenic strains of S. cerevisiae differing only at loci involved in DNA repair functions were exposed to aminopterin and sulfanilamide to induce thymidine deprivation. Cultures were irradiated and survival determined by clonogenic survival assay.

RESULTS

Strains lacking uracil base excision repair (BER) activities demonstrated less radiosensitization than the parental strain. Mutant strains continued to show partial radiosensitization with aminopterin treatment. Mutants deficient in BER of both uracil and oxidatively damaged bases did not demonstrate radiosensitization. A recombination deficient rad52 mutant strain was markedly sensitive to radiation; addition of aminopterin increased radiosensitivity only slightly. Radiosensitization observed in rad52 mutants was also abolished by deletion of the APN1, NTG1, and NTG2 genes.

CONCLUSION

These data suggest radiosensitization during thymidine depletion is the result of BER activities directed at both uracil and oxidatively damaged bases.

Gemcitabine radiosensitization after high-dose samarium for osteoblastic osteosarcoma

Osteoblastic metastases and osteosarcoma can avidly concentrate bone-seeking radiopharmaceuticals. We sought to increase effectiveness of high-dose (153)Samarium ethylenediaminetetramethylenephosphonate (153Sm-EDTMP, Quadramet) on osteosarcomas using a radiosensitizer, gemcitabine. Fourteen patients with osteoblastic lesions were treated with 30 mCi/kg 153Sm-EDTMP. Gemcitabine was administered 1 day after samarium infusion. Residual total body radioactivity was within the safe range of <3.6 mCi on day +14 (1.1 +/- 0.4 mCi; range, 0.67-1.8 mCi). All patients received autologous stem cell reinfusion 2 weeks after 153Sm to correct expected grade 4 hematopoietic toxicity. Peripheral blood progenitor cells were infused in 11 patients; three patients had marrow infused. Blood count recovery was uneventful after peripheral blood progenitor cells in 11 of 11 patients. Toxicity from a single infusion of gemcitabine (1,500 mg/m2) in combination with 153Sm-EDTMP was minimal (pancytopenia). However, toxicity from a daily gemcitabine regimen (250 mg/m2/d x 4-5 days) was excessive (grade 3 mucositis) in one of two patients. There were no reported episodes of hemorrhagic cystitis (hematuria) or nephrotoxicity. At the 6- to 8-week follow-up, there were six partial remissions, two mixed responses, and six patients with progressive disease. In the 12 patients followed >1 year, there have been no durable responses. Thus, although high-dose 153Sm-EDTMP + gemcitabine has moderate palliative activity (improved pain; radiologic responses) in this poor-risk population, additional measures of local and systemic control are required for durable control of relapsed osteosarcoma with osteoblastic lesions. The strategy of radioactive drug binding to a target followed by a radiosensitizer may provide synergy and improved response rate.

Biodistribution and pharmacokinetics of the 19F-labeled radiosensitizer 3-aminobenzamide: assessment by 19F MR imaging

3-Aminobenzamide (3-ABA) is a potent radiosensitizer that inhibits the repair of DNA strand breaks. The aim of this study was to monitor the biodistribution and pharmacokinetics of a fluorinated 3-ABA derivative in tumor-bearing rats by magnetic resonance imaging (MRI). To this end, 3-ABA was labeled with fluorine-19 by trifluoroethylation [3-amino-N-2,2,2-trifluoroethylbenzamide (3-ABA-TFE)], which only slightly increased the cytotoxicity of the compound as demonstrated by colony-forming assays. After intraperitoneal injection of 400 mg/kg BW 3-ABA-TFE to nine Copenhagen rats with Dunning prostate adenocarcinoma, (19)F MR images were acquired at a whole-body MR system with a spatial sampling of 10 x 10 x 15 mm(3). While 3-ABA-TFE was observed in all major organs and the muscular system, only a small and heterogeneous signal could be detected in the adenocarcinoma. Serial MR measurements yielded maximum tissue signals about 2 days after 3-ABA-TFE administration. At this time point, the mean muscle-to-liver and tumor-to-liver signal ratio was 0.31+/-0.07 and 0.11+/-0.04, respectively. Application of the (19)F MRI strategy makes it possible to measure the biodistribution and pharmacokinetics of 3-ABA-TFE in individual animals in a longitudinal manner. The results obtained for the prostate adenocarcinoma indicate that delivery of 3-ABA-TFE to solid tumors may be seriously hampered by tumor-specific factors and that the intratumoral uptake of the substance may be lower than in normal tissues. Therefore, the development of effective carrier systems is mandatory to improve tumor-selective delivery.

Gemcitabine twice weekly as a radiosensitiser for the treatment of brain metastases in patients with carcinoma: a phase I study

Conventional treatment for brain metastases (BM) is whole-brain radiotherapy (WBRT). Efficacy is poor. It might be increased by a potent radiosensitiser such as gemcitabine which is believed to cross the disrupted blood–brain barrier. Primary objective of this study was to determine the maximum tolerated dose (MTD) of twice weekly gemcitabine given concurrently with WBRT. Patients with BM from carcinoma were included. The dose of WBRT was 30 Gys (10 daily fractions). Gemcitabine was given 2–4 h prior to WBRT on days 1 and 8 for the first cohort of patients and then on days 1, 4, 8 and 11. Starting dose was 25 mg m⁻², escalated by 12.5 mg m⁻² increments. At least three patients were included per level. Dose limiting toxicity (DLT) was defined as grade 4 haematological or grade ⩾3 nonhaematological toxicity. A total of 25 patients were included; 74% had a PS 1 (ECOG). In all, 23 had non-small-cell lung cancer, six colorectal, four breast, two renal cell and one oesophageal carcinoma. A total of 92% had concurrent extracranial disease. Six had single BM, 13 had two or three BM and six multiple. Up to 50 mg m⁻² (level 4) no DLT was observed. At 62.5 mg m⁻², one out of six patients developed DLT (thrombocytopenia-bleeding). The next dose level (75 mg m⁻²) was abandoned after grade 4 bone marrow toxicity (fatal neutropenic sepsis) was seen in one out of two patients. So that the dose of 50 mg m⁻² will be taken forward for further study.

CT-guided interstitial brachytherapy of liver malignancies alone or in combination with thermal ablation: phase I-II results of a novel technique

PURPOSE

To assess the safety and efficacy of CT-guided brachytherapy alone or in combination with laser-induced thermotherapy (LITT) in patients with liver malignancies.

METHODS AND MATERIALS

Thirty-seven patients presented with 36 liver metastases and two primary liver carcinomas. Twenty-one patients were treated with CT-guided high-dose-rate brachytherapy alone using a 192Ir source. Sixteen patients received brachytherapy directly after MRI-guided LITT. The indications for brachytherapy alone were a tumor size >5 cm, adjacent central bile duct or adjacent major vessels causing unfavorable cooling effects for thermal ablation, and technical failures of LITT. The dosimetry for brachytherapy was performed using three-dimensional CT data acquired after percutaneous applicator positioning. On average, a minimal dose of 17 Gy inside the tumor margin was applied (range, 10-20 Gy).

RESULTS

The mean tumor size was 4.6 cm (range, 2.5-11 cm). The mean liver volume receiving > or =5 Gy was 16% (range, 2-40%) of the total liver. Severe complications were recorded in 2 patients (5%). One patient developed acute liver failure possibly related to accidental continuation of oral capecitabine treatment. Another patient demonstrated obstructive jaundice owing to tumor edema after irradiation of a metastasis adjacent to the bile duct bifurcation. A commonly encountered moderate increase of liver enzymes was greatest in patients with combined treatment. The local control rate after 6 months was 73% and 87% for combined treatment and brachytherapy alone, respectively.

CONCLUSION

CT-guided brachytherapy using three-dimensional CT data for dosimetry is safe and effective alone or in combination with LITT. Brachytherapy as a stand-alone treatment displayed genuine advantages over thermal tumor ablation.

Overcoming the hypoxic barrier to radiation therapy with anaerobic bacteria

The low level of oxygenation within tumors is a major cause of radiation treatment failures. We theorized that anaerobic bacteria that can selectively destroy the hypoxic regions of tumors would enhance the effects of radiation. To test this hypothesis, we used spores of Clostridium novyi-NT to treat transplanted tumors in mice. The bacteria were found to markedly improve the efficacy of radiotherapy in several of the mouse models tested. Enhancement was noted with external beam radiation derived from a Cs-137 source, systemic radioimmunotherapy with an I-131-conjugated monoclonal antibody, and a previously undescribed form of experimental brachytherapy using plaques loaded with I-125 seeds. C. novyi-NT spores added little toxicity to the radiotherapeutic regimens, and the combination resulted in long-term remissions in a significant fraction of animals.

Chemoradiotherapy: emerging treatment improvement strategies

BACKGROUND

The use of chemotherapeutic drugs in combination with radiotherapy has become a common strategy for the treatment of advanced cancer. Solid evidence exists showing that chemotherapy administered during the course of radiotherapy (concurrent chemoradiotherapy) increases both local tumor control and patient survival in a number of cancer sites, including head and neck cancer. These therapy improvements, however, have been achieved at the expense of considerable toxicity, which underscores the need for further improvements.

METHODS

The current status of chemoradiotherapy clinical trials for head and neck cancer and research on the emerging treatment improvements were reviewed. A review of potential treatment improvement strategies focused on preclinical investigations on newer chemotherapeutic agents, notably taxanes and nucleoside analogues, as well as on molecular targets such as epidermal growth factor receptor (EGFR) or cyclooxygenase-2 (COX-2) enzyme.

RESULTS

Concurrent, but not induction (drugs given before radiotherapy), chemoradiotherapy improves locoregional tumor control and survival benefit in head and neck carcinoma relative to radiotherapy alone. In comparison, both concurrent and induction chemoradiotherapy showed therapeutic advantage over radiotherapy alone in the treatment of lung cancer. These therapeutic improvements were achieved with standard chemotherapeutic drugs, most commonly cisplatin-based chemotherapy. Biologically, chemotherapy interacts with radiation through a number of mechanisms, including inhibition of cellular repair, cell cycle effects, and inhibition of tumor cell regeneration. Potential avenues emerged to further improve chemoradiotherapy. One of these involves the newer chemotherapeutic agents, taxanes and nucleoside analogues, which in preclinical studies exhibited strong tumor radiosensitization and therapeutic gain. The clinical benefit of these agents is currently under testing. Another approach for improvement of chemoradiotherapy consists of inhibiting molecules selectively or preferentially expressed on tumor cells, such as EGFR and COX-2, both shown to render cellular resistance to drugs or radiation. Agents that selectively inhibit these molecules are becoming available at a rapid rate, and many of them have been shown in preclinical testing to be highly effective in improving tumor radioresponse or chemoresponse without affecting normal tissues.

CONCLUSIONS

Concurrent chemoradiotherapy, using standard chemotherapeutic agents, has emerged as an effective treatment for advanced cancer, but unfortunately at the expense of considerable increase in normal tissue toxicity. There are a number of potential emerging treatment strategies to further improve chemoradiotherapy. One consists of using newer chemotherapeutic drugs, which in preclinical studies are potent enhancers of tumor radioresponse. Another approach consists of targeting EGFR or COX-2 with selective inhibitors of these molecules.

The mechanism of action of radiosensitization of conventional chemotherapeutic agents

It is not an exaggeration to state that most of the advances in curing cancer in the last decade have come from successful combinations of conventional chemotherapeutic agents with radiation therapy. Further improvements in therapy will depend on understanding the mechanisms by which chemotherapy improves the effectiveness of radiation in model systems and in patients. In this review, we discuss the mechanisms of action of the fluoropyrimidines, gemcitabine, and the platinums. The fluoropyrimidines (5-fluorouracil and fluorodeoxyuridine) increase the effectiveness of radiation chiefly when given before and during radiation. Increased radiation sensitivity occurs in cells that progress inappropriately into S phase in the presence of drug, suggesting a key role for dysregulation of S-phase checkpoints. Gemcitabine may radiosensitize by a similar mechanism, although the relative roles of specific DNA repair pathways (such as homologous end rejoining) and of apoptosis remain to be determined. For both of these categories of drugs, sensitization probably results when cells that are progressing inappropriately through S phase misrepair DNA damage inflicted by radiation. Thus, loss of the S-phase checkpoint in cancer cells may provide the molecular basis for selective killing of tumors compared with normal tissues. Cisplatin has multiple effects on cells, such as adduct formation and DNA damage repair inhibition, but the mechanism for selectivity against cancer cells compared with normal cells is not yet determined. The identification of the enzymatic targets for these drugs offers the potential to develop predictive assays for response and to develop methods of imaging the progress of therapy.

Antimetabolite incorporation into DNA: structural and thermodynamic basis for anticancer activity

Antimetabolites are a class of effective anticancer drugs that structurally resemble naturally occurring biochemicals and interfere in essential biochemical processes. In this review, the recent literature describing investigations of the structural and thermodynamic basis for the anticancer activity of three antipyrimidines [1-beta-D-arabinofuranosyl cytidine (AraC). 2',2'-difluoro deoxycytidine (dFdC), and 5-fluoro-2'-deoxyuridine (FdUrd)] is summarized. Our laboratory, and others, have shown that misincorporation of any of these three antipyrimidines into DNA perturbs the structure and decreases the stability of duplex DNA. These data are useful for rationalizing the effects of antipyrimidine misincorporation on the activities of proteins required for DNA replication and repair such as DNA topoisomerase 1 and DNA polymerases. The studies completed to date and summarized in this review demonstrate the utility of investigations into the structure-function relationships between antipyrimidine-substituted DNA complexed with DNA-modifying proteins for the purpose of understanding the basis for effective antipyrimidine cancer chemotherapy and the future design of novel anticancer drugs.