Modulation of cell death in the tumor microenvironment

Enhanced bacterial cancer therapy delivering therapeutic RNA interference of c-Myc

BACKGROUND

Bacterial cancer therapy was first trialled in patients at the end of the nineteenth century. More recently, tumour-targeting bacteria have been harnessed to deliver plasmid-expressed therapeutic interfering RNA to a range of solid tumours. A major limitation to clinical translation of this is the short-term nature of RNA interference in vivo due to plasmid instability. To overcome this, we sought to develop tumour-targeting attenuated bacteria that stably express shRNA by virtue of integration of an expression cassette within the bacterial chromosome and demonstrate therapeutic efficacy in vitro and in vivo.

RESULTS

The attenuated tumour targeting Salmonella typhimurium SL7207 strain was modified to carry chromosomally integrated shRNA expression cassettes at the xylA locus. The colorectal cancer cell lines SW480, HCT116 and breast cancer cell line MCF7 were used to demonstrate the ability of these modified strains to perform intracellular infection and deliver effective RNA and protein knockdown of the target gene c-Myc. In vivo therapeutic efficacy was demonstrated using the Lgr5creERT2Apcflx/flx and BlgCreBrca2flx/flp53flx/flx orthotopic immunocompetent mouse models of colorectal and breast cancer, respectively. In vitro co-cultures of breast and colorectal cancer cell lines with modified SL7207 demonstrated a significant 50-95% (P < 0.01) reduction in RNA and protein expression with SL7207/c-Myc targeted strains. In vivo, following establishment of tumour tissue, a single intra-peritoneal administration of 1 × 106 CFU of SL7207/c-Myc was sufficient to permit tumour colonisation and significantly extend survival with no overt toxicity in control animals.

CONCLUSIONS

In summary we have demonstrated that tumour tropic bacteria can be modified to safely deliver therapeutic levels of gene knockdown. This technology has the potential to specifically target primary and secondary solid tumours with personalised therapeutic payloads, providing new multi-cancer detection and treatment options with minimal off-target effects. Further understanding of the tropism mechanisms and impact on host immunity and microbiome is required to progress to clinical translation.

Application of nanotechnology in reversing therapeutic resistance and controlling metastasis of colorectal cancer

Colorectal cancer (CRC) is the most common digestive malignancy across the world. Its first-line treatments applied in the routine clinical setting include surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy. However, resistance to therapy has been identified as the major clinical challenge that fails the treatment method, leading to recurrence and distant metastasis. An increasing number of studies have been attempting to explore the underlying mechanisms of the resistance of CRC cells to different therapies, which can be summarized into two aspects: (1) The intrinsic characters and adapted alterations of CRC cells before and during treatment that regulate the drug metabolism, drug transport, drug target, and the activation of signaling pathways; and (2) the suppressive features of the tumor microenvironment (TME). To combat the issue of therapeutic resistance, effective strategies are warranted with a focus on the restoration of CRC cells’ sensitivity to specific treatments as well as reprogramming impressive TME into stimulatory conditions. To date, nanotechnology seems promising with scope for improvement of drug mobility, treatment efficacy, and reduction of systemic toxicity. The instinctive advantages offered by nanomaterials enable the diversity of loading cargoes to increase drug concentration and targeting specificity, as well as offer a platform for trying the combination of different treatments to eventually prevent tumor recurrence, metastasis, and reversion of therapy resistance. The present review intends to summarize the known mechanisms of CRC resistance to chemotherapy, radiotherapy, immunotherapy, and targeted therapy, as well as the process of metastasis. We have also emphasized the recent application of nanomaterials in combating therapeutic resistance and preventing metastasis either by combining with other treatment approaches or alone. In summary, nanomedicine is an emerging technology with potential for CRC treatment; hence, efforts should be devoted to targeting cancer cells for the restoration of therapeutic sensitivity as well as reprogramming the TME. It is believed that the combined strategy will be beneficial to achieve synergistic outcomes contributing to control and management of CRC in the future.

Multicellular Ovarian Cancer Model for Evaluation of Nanovector Delivery in Ascites and Metastatic Environments

A novel multicellular model composed of epithelial ovarian cancer and fibroblast cells was developed as an in vitro platform to evaluate nanovector delivery and ultimately aid the development of targeted therapies. We hypothesized that the inclusion of peptide-based scaffold (PuraMatrix) in the spheroid matrix, to represent in vivo tumor microenvironment alterations along with metastatic site conditions, would enhance spheroid cell growth and migration and alter nanovector transport. The model was evaluated by comparing the growth and migration of ovarian cancer cells exposed to stromal cell activation and tissue hypoxia. Fibroblast activation was achieved via the TGF-β1 mediated pathway and tissue hypoxia via 3D spheroids incubated in hypoxia. Surface-modified nanovector transport was assessed via fluorescence and confocal microscopy. Consistent with previous in vivo observations in ascites and at distal metastases, spheroids exposed to activated stromal microenvironment were denser, more contractile and with more migratory cells than nonactivated counterparts. The hypoxic conditions resulted in negative radial spheroid growth over 5 d compared to a radial increase in normoxia. Nanovector penetration attenuated in PuraMatrix regardless of surface modification due to a denser environment. This platform may serve to evaluate nanovector transport based on ovarian ascites and metastatic environments, and longer term, it provide a means to evaluate nanotherapeutic efficacy.

Epigenetic Regulation of Angiogenesis in Development and Tumors Progression: Potential Implications for Cancer Treatment

Angiogenesis is a multi-stage process of new blood vessel development from pre-existing vessels toward an angiogenic stimulus. The process is essential for tissue maintenance and homeostasis during embryonic development and adult life as well as tumor growth. Under normal conditions, angiogenesis is involved in physiological processes, such as wound healing, cyclic regeneration of the endometrium, placental development and repairing certain cardiac damage, in pathological conditions, it is frequently associated with cancer development and metastasis. The control mechanisms of angiogenesis in carcinogenesis are tightly regulated at the genetic and epigenetic level. While genetic alterations are the critical part of gene silencing in cancer cells, epigenetic dysregulation can lead to repression of tumor suppressor genes or oncogene activation, becoming an important event in early development and the late stages of tumor development, as well. The global alteration of the epigenetic spectrum, which includes DNA methylation, histone modification, chromatin remodeling, microRNAs, and other chromatin components, is considered one of the hallmarks of cancer, and the efforts are concentrated on the discovery of molecular epigenetic markers that identify cancerous precursor lesions or early stage cancer. This review aims to highlight recent findings on the genetic and epigenetic changes that can occur in physiological and pathological angiogenesis and analyze current knowledge on how deregulation of epigenetic modifiers contributes to tumorigenesis and tumor maintenance. Also, we will evaluate the clinical relevance of epigenetic markers of angiogenesis and the potential use of "epi-drugs" in modulating the responsiveness of cancer cells to anticancer therapy through chemotherapy, radiotherapy, immunotherapy and hormone therapy as anti-angiogenic strategies in cancer.

Bcl-2/Bcl-xL inhibitor ABT-263 overcomes hypoxia-driven radioresistence and improves radiotherapy

Hypoxia, a characteristic of most human solid tumors, is a major obstacle to successful radiotherapy. While moderate acute hypoxia increases cell survival, chronic cycling hypoxia triggers adaptation processes, leading to the clonal selection of hypoxia-tolerant, apoptosis-resistant cancer cells. Our results demonstrate that exposure to acute and adaptation to chronic cycling hypoxia alters the balance of Bcl-2 family proteins in favor of anti-apoptotic family members, thereby elevating the apoptotic threshold and attenuating the success of radiotherapy. Of note, inhibition of Bcl-2 and Bcl-xL by BH3-mimetic ABT-263 enhanced the sensitivity of HCT116 colon cancer and NCI-H460 lung cancer cells to the cytotoxic action of ionizing radiation. Importantly, we observed this effect not only in normoxia, but also in severe hypoxia to a similar or even higher extent. ABT-263 furthermore enhanced the response of xenograft tumors of control and hypoxia-selected NCI-H460 cells to radiotherapy, thereby confirming the beneficial effect of combined treatment in vivo. Targeting the Bcl-2 rheostat with ABT-263, therefore, is a particularly promising approach to overcome radioresistance of cancer cells exposed to acute or chronic hypoxia with intermittent reoxygenation. Moreover, we found intrinsic as well as ABT-263- and irradiation-induced regulation of Bcl-2 family members to determine therapy sensitivity. In this context, we identified Mcl-1 as a resistance factor that interfered with apoptosis induction by ABT-263, ionizing radiation, and combinatorial treatment. Collectively, our findings provide novel insights into the molecular determinants of hypoxia-mediated resistance to apoptosis and radiotherapy and a rationale for future therapies of hypoxic and hypoxia-selected tumor cell fractions.

The promise and challenge of cancer microbiome research

Many microbial agents have been implicated as contributors to cancer genesis and development, and the search to identify and characterize new cancer-related organisms is ongoing. Modern developments in methodologies, especially culture-independent approaches, have accelerated and driven this research. Recent work has shed light on the multifaceted role that the community of organisms in and on the human body plays in cancer onset, development, detection, treatment, and outcome. Much remains to be discovered, however, as methodological variation and functional testing of statistical correlations need to be addressed for the field to advance.

Characterisation of microbiota in saliva, bronchoalveolar lavage fluid, non-malignant, peritumoural and tumour tissue in non-small cell lung cancer patients: a cross-sectional clinical trial

BACKGROUND

While well-characterised on its molecular base, non-small cell lung cancer (NSCLC) and its interaction with local microbiota remains scarcely explored. Moreover, current studies vary in source of lung microbiota, from bronchoalveolar lavage fluid (BAL) to tissue, introducing potentially differing results. Therefore, the objective of this study was to provide detailed characterisation of the oral and multi-source lung microbiota of direct interest in lung cancer research. Since lung tumours in lower lobes (LL) have been associated with decreased survival, characteristics of the microbiota in upper (UL) and lower tumour lobes have also been examined.

METHODS

Using 16S rRNA gene sequencing technology, we analysed microbiota in saliva, BAL (obtained directly on excised lobe), non-malignant, peritumoural and tumour tissue from 18 NSCLC patients eligible for surgical treatment. Detailed taxonomy, diversity and core members were provided for each microbiota, with analysis of differential abundance on all taxonomical levels (zero-inflated binomial general linear model with Benjamini-Hochberg correction), between samples and lobe locations.

RESULTS

Diversity and differential abundance analysis showed clear separation of oral and lung microbiota, but more importantly, of BAL and lung tissue microbiota. Phylum Proteobacteria dominated tissue samples, while Firmicutes was more abundant in BAL and saliva (with class Clostridia and Bacilli, respectively). However, all samples showed increased abundance of phylum Firmicutes in LL, with decrease in Proteobacteria. Also, clades Actinobacteria and Flavobacteriia showed inverse abundance between BAL and extratumoural tissues depending on the lobe location. While tumour microbiota seemed the least affected by location, peritumoural tissue showed the highest susceptibility with markedly increased similarity to BAL microbiota in UL. Differences between the three lung tissues were however very limited.

CONCLUSIONS

Our results confirm that BAL harbours unique lung microbiota and emphasise the importance of the sample choice for lung microbiota analysis. Further, limited differences between the tissues indicate that different local tumour-related factors, such as tumour type, stage or associated immunity, might be the ones responsible for microbiota-shaping effect. Finally, the "shift" towards Firmicutes in LL might be a sign of increased pathogenicity, as suggested in similar malignancies, and connected to worse prognosis of the LL tumours.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT03068663. Registered February 27, 2017.

Enabling cell recovery from 3D cell culture microfluidic devices for tumour microenvironment biomarker profiling

The tumour microenvironment (TME) has recently drawn much attention due to its profound impact on tumour development, drug resistance and patient outcome. There is an increasing interest in new therapies that target the TME. Nonetheless, most established in vitro models fail to include essential cues of the TME. Microfluidics can be used to reproduce the TME in vitro and hence provide valuable insight on tumour evolution and drug sensitivity. However, microfluidics remains far from well-established mainstream molecular and cell biology methods. Therefore, we have developed a quick and straightforward collagenase-based enzymatic method to recover cells embedded in a 3D hydrogel in a microfluidic device with no impact on cell viability. We demonstrate the validity of this method on two different cell lines in a TME microfluidic model. Cells were successfully retrieved with high viability, and we characterised the different cell death mechanisms via AMNIS image cytometry in our model.

Hypoxia Regulation of Phosphokinases and the Prognostic Value of pAKT in Breast Cancer

Tumor hypoxia results in poor treatment response and is an indicator of poor outcome in cancer patients. TRIB3 is a hypoxia-upregulated protein involved in the ability of breast cancer cells to survive in hypoxic conditions. It is also involved in the prognosis of cancer patients, possibly by affecting several kinase-signaling pathways. We set out to establish which kinase-signaling pathways are regulated by hypoxia and whether these kinases are relevant for breast cancer prognosis. Using a phosphokinase antibody array comparing cells cultured under hypoxic conditions with those cultured during normoxia, we found that the phosphorylation status of ERK1/2, AKT, p70 S6 kinase, Lck and STAT3 was altered in both MCF7 and MDA-MB-231 breast cancer cells. Using Western blotting, we found that phosphorylated AKT (pAKT) increased in hypoxic conditions. Knockdown of TRIB3 attenuated this effect of hypoxia on AKT activation. Both pAKT and TRIB3 were expressed in pimonidazole-positive, hypoxic areas of human breast cancer tumors. In breast cancer patients significantly lower 5-year disease-free survival was observed for the pAKT-positive compared to the pAKT-negative group (64.6% vs 86.1%, p=0.03).

In conclusion, the phosphorylation status of AKT is increased in hypoxic conditions and TRIB3 knockdown attenuates this response. Furthermore, pAKT expression denotes a worse prognosis in breast cancer patients. The hypoxia-related activation of AKT could explain the resistance to various treatments including chemotherapy and radiotherapy.

Bacterial Therapy of Cancer: Promises, Limitations, and Insights for Future Directions

Spontaneous tumors regression has been associated with microbial infection for 100s of years and inspired the use of bacteria for anticancer therapy. Dr. William B. Coley (1862-1936), a bone- sarcoma surgeon, was a pioneer in treating his patients with both live bacterial-based and mixture of heat-killed bacteria known as "Coley's toxins." Unfortunately, Coley was forced to stop his work which interrupted this field for about half a century. Currently, several species of bacteria are being developed against cancer. The bacterial species, their genetic background and their infectious behavior within the tumor microenvironment are thought to be relevant factors in determining their anti-tumor effectiveness in vivo. In this perspective article we will update the most promising results achieved using bacterial therapy (alone or combined with other strategies) in clinically-relevant animal models of cancer and critically discuss the impact of the bacterial variants, route of administration and mechanisms of bacteria-cancer-cell interaction. We will also discuss strategies to apply this information using modern mouse models, molecular biology, genetics and imaging for future bacterial therapy of cancer patients.

Predicting tumor hypoxia in non-small cell lung cancer by combining CT, FDG PET and dynamic contrast-enhanced CT

BACKGROUND

Most solid tumors contain inadequately oxygenated (i.e., hypoxic) regions, which tend to be more aggressive and treatment resistant. Hypoxia PET allows visualization of hypoxia and may enable treatment adaptation. However, hypoxia PET imaging is expensive, time-consuming and not widely available. We aimed to predict hypoxia levels in non-small cell lung cancer (NSCLC) using more easily available imaging modalities: FDG-PET/CT and dynamic contrast-enhanced CT (DCE-CT).

MATERIAL AND METHODS

For 34 NSCLC patients, included in two clinical trials, hypoxia HX4-PET/CT, planning FDG-PET/CT and DCE-CT scans were acquired before radiotherapy. Scans were non-rigidly registered to the planning CT. Tumor blood flow (BF) and blood volume (BV) were calculated by kinetic analysis of DCE-CT images. Within the gross tumor volume, independent clusters, i.e., supervoxels, were created based on FDG-PET/CT. For each supervoxel, tumor-to-background ratios (TBR) were calculated (median SUV/aorta SUV_mean) for HX4-PET/CT and supervoxel features (median, SD, entropy) for the other modalities. Two random forest models (cross-validated: 10 folds, five repeats) were trained to predict the hypoxia TBR; one based on CT, FDG, BF and BV, and one with only CT and FDG features. Patients were split in a training (trial NCT01024829) and independent test set (trial NCT01210378). For each patient, predicted, and observed hypoxic volumes (HV) (TBR > 1.2) were compared.

RESULTS

Fifteen patients (3291 supervoxels) were used for training and 19 patients (1502 supervoxels) for testing. The model with all features (RMSE training: 0.19 ± 0.01, test: 0.27) outperformed the model with only CT and FDG-PET features (RMSE training: 0.20 ± 0.01, test: 0.29). All tumors of the test set were correctly classified as normoxic or hypoxic (HV > 1 cm³) by the best performing model.

CONCLUSIONS

We created a data-driven methodology to predict hypoxia levels and hypoxia spatial patterns using CT, FDG-PET and DCE-CT features in NSCLC. The model correctly classifies all tumors, and could therefore, aid tumor hypoxia classification and patient stratification.

The microbiome in anti-cancer therapy

The commensal microbiome constitutes an important modulator of host physiology and risk of disease, including cancer development and progression. Lately, the microbiome has been suggested to modulate the efficacy of anti-cancer treatment. Examples include chemotherapy and total body irradiation-induced barrier function disruption, leading to microbial efflux that drives activation of anti-tumorigenic T cells; Microbiome-driven release of reactive oxygen species contributing to the efficacy of platinum salts; and microbiome-induced immune priming promoting the anti-tumor effects of alkylating chemotherapy and immune checkpoint inhibitors. Furthermore, selected commensals are able to colonize solid tumors. This 'tumor microbiome' may further impact local tumor responses to treatment and potentially be harnessed for tumor-specific targeting and therapeutic delivery. In this review, we present recent advances in understanding of the intricate role of microbiome in modulating efficacy of a number of anti-cancer treatments, and discuss how anti-cancer treatment approaches utilizing the tumor microbiome may enhance oncological treatment efficacy.

A phase 1 'window-of-opportunity' trial testing evofosfamide (TH-302), a tumour-selective hypoxia-activated cytotoxic prodrug, with preoperative chemoradiotherapy in oesophageal adenocarcinoma patients

Background

Neo-adjuvant chemoradiotherapy followed by surgery is the standard treatment with curative intent for oesophageal cancer patients, with 5-year overall survival rates up to 50 %. However, patients’ quality of life is severely compromised by oesophagectomy, and eventually many patients die due to metastatic disease.

Most solid tumours, including oesophageal cancer, contain hypoxic regions that are more resistant to chemoradiotherapy. The hypoxia-activated prodrug evofosfamide works as a DNA-alkylating agent under these hypoxic conditions, which directly kills hypoxic cancer cells and potentially minimizes resistance to conventional therapy. This drug has shown promising results in several clinical studies when combined with chemotherapy. Therefore, in this phase I study we investigate the safety of evofosfamide added to the chemoradiotherapy treatment of oesophageal cancer.

Methods/Design

A phase I, non-randomized, single-centre, open-label, 3 + 3 trial with repeated hypoxia PET imaging, will test the safety of evofosfamide in combination with neo-adjuvant chemoradiotherapy in potentially resectable oesophageal adenocarcinoma patients. Investigated dose levels range from 120 mg/m2 to 340 mg/m2. Evofosfamide will be administered one week before the start of chemoradiotherapy (CROSS-regimen) and repeated weekly up to a total of six doses. PET/CT acquisitions with hypoxia tracer ¹⁸F-HX4 will be made before and after the first administration of evofosfamide, allowing early assessment of changes in hypoxia, accompanied with blood sampling to measure hypoxia blood biomarkers. Oesophagectomy will be performed according to standard clinical practice.

Higher grade and uncommon non-haematological, haematological, and post-operative toxicities are the primary endpoints according to the CTCAEv4.0 and Clavien-Dindo classifications. Secondary endpoints are reduction in hypoxic fraction based on ¹⁸F-HX4 imaging, pathological complete response, histopathological negative circumferential resection margin (R0) rate, local and distant recurrence rate, and progression free and overall survival.

Discussion

This is the first clinical trial testing evofosfamide in combination with chemoradiotherapy. The primary objective is to determine the dose limiting toxicity of this combined treatment and herewith to define the maximum tolerated dose and recommended phase 2 dose for future clinical studies. The addition of non-invasive repeated hypoxia imaging (‘window-of-opportunity’) enables us to identify the biologically effective dose. We believe this approach could also be used for other hypoxia targeted drugs.

Trial registration

ClinicalTrials.gov Identifier: NCT02598687.

NIR Spectroscopic Detection of Breast Cancer

Near infrared spectroscopy (NIRS) utilizes intrinsic optical absorption signals of blood, water, and lipid concentration available in the NIR window (600–1000 nm) as well as a developing array of extrinsic organic compounds to detect and localize cancer. This paper reviews optical cancer detection made possible through high tumor-tissue signal-to-noise ratio (SNR) and providing biochemical and physiological data in addition to those obtained via other methods.

NIRS detects cancers in vivo through a combination of blood volume and oxygenation from measurements of oxy- and deoxy-hemoglobin giving signals of tumor angiogenesis and hypermetabolism. The Chance lab tends towards CW breast cancer systems using manually scannable detectors with calibrated low pressure tissue contact. These systems calculate angiogenesis and hypermetabolism by using a pair of wavelengths and referencing the mirror image position of the contralateral breast to achieve high ROC/AUC. Time domain and frequency domain spectroscopy were also used to study similar intrinsic breast tumor characteristics such as high blood volume. Other NIRS metrics are water-fat ratio and the optical scattering coefficient. An extrinsic FDA approved dye, ICG, has been used to measure blood pooling with extravasation, similar to Gadolinium in MRI.

A key future development in NIRS will be new Molecular Beacons targeting cancers and fluorescing in the NIR window to enhance in vivo tumor-tissue ratios and to afford biochemical specificity with the potential for effective photodynamic anti-cancer therapies.

Solid tumors provide niche-specific conditions that lead to preferential growth of Salmonella

Therapeutic attenuated strains of Salmonella Typhimurium target and eradicate tumors in mouse models. However, the mechanism of S. Typhimurium for tumor targeting is still poorly understood. We performed a high-throughput screening of single-gene deletion mutants of S. Typhimurium in an orthotopic, syngeneic murine mammary model of breast cancer. The mutants under selection in this system were classified into functional categories to identify bacterial processes involved in Salmonella accumulation within tumors. Niche-specific genes involved in preferential tumor colonization were identified and exemplars were confirmed by competitive infection assays. Our results show that the chemotaxis gene cheY and the motility genes motAB confer an advantage for colonization of Salmonella within orthotopic syngeneic breast tumors. In addition, eutC, a gene belonging to the ethanolamine metabolic pathway, also confers an advantage for Salmonella within tumors, perhaps by exploiting either ethanolamine or an alternative nutrient in the inflamed tumor environment.

A three-dimensional engineered tumour for spatial snapshot analysis of cell metabolism and phenotype in hypoxic gradients

The profound metabolic reprogramming that occurs in cancer cells has been investigated primarily in two-dimensional cell cultures, which fail to recapitulate spatial aspects of cell-to-cell interactions as well as tissue gradients present in three-dimensional tumours. Here, we describe an engineered model to assemble three-dimensional tumours by rolling a scaffold-tumour composite strip. By unrolling the strip, the model can be rapidly disassembled for snapshot analysis, allowing spatial mapping of cell metabolism in concert with cell phenotype. We also show that the establishment of oxygen gradients within samples that are shaped by oxygen-dependent signalling pathways, as well as the consequential variations in cell growth, response to hypoxic gradients extending from normoxia to severe hypoxia, and therapy responsiveness, are consistent with those of tumours in vivo. Moreover, by using liquid chromatography tandem mass spectrometry, we mapped cellular metabolism and identified spatially defined metabolic signatures of cancer cells to reveal both known and novel metabolic responses to hypoxia.

Lysyl oxidase mediates hypoxia-induced radioresistance in non-small cell lung cancer A549 cells

Hypoxia-induced radioresistance has been well known as the main obstacle in cancer radiotherapy. Lysyl oxidase (LOX) was previously demonstrated to play an important role in hypoxia-induced biological behaviors, such as metastasis and angiogenesis, through hypoxia-inducible factor-1α (HIF-1α), which is an important contributing factor to radioresistance in tumor cells. However, how LOX plays a role in hypoxia-induced radioresistance has yet to be determined. Here, we found that LOX expression was in accordance with HIF-1α expression, and LOX expression at the mRNA and protein level, and enzymatic activity were remarkably upregulated in the hypoxic A549 cells, compared with normoxic A549 cells. Inhibition of LOX resulted in the reduction of the ability to repair double-stranded breaks (DSBs), promotion of apoptosis, relief of G2/M cycle arrest, and eventually reduction of hypoxia-induced radioresistance in the hypoxic A549 cells. This suggests that LOX may play an important role in hypoxia-induced radioresistance. Together, our results might suggest a novel potential therapeutic target in the management of non-small cell lung cancer (NSCLC).

Repeatability of hypoxia PET imaging using [¹⁸F]HX4 in lung and head and neck cancer patients: a prospective multicenter trial

PURPOSE

Hypoxia is an important factor influencing tumor progression and treatment efficacy. The aim of this study was to investigate the repeatability of hypoxia PET imaging with [(18)F]HX4 in patients with head and neck and lung cancer.

METHODS

Nine patients with lung cancer and ten with head and neck cancer were included in the analysis (NCT01075399). Two sequential pretreatment [(18)F]HX4 PET/CT scans were acquired within 1 week. The maximal and mean standardized uptake values (SUVmax and SUVmean) were defined and the tumor-to-background ratios (TBR) were calculated. In addition, hypoxic volumes were determined as the volume of the tumor with a TBR >1.2 (HV1.2). Bland Altman analysis of the uptake parameters was performed and coefficients of repeatability were calculated. To evaluate the spatial repeatability of the uptake, the PET/CT images were registered and a voxel-wise comparison of the uptake was performed, providing a correlation coefficient.

RESULTS

All parameters of [(18)F]HX4 uptake were significantly correlated between scans: SUVmax (r = 0.958, p < 0.001), SUVmean (r = 0.946, p < 0.001), TBRmax (r = 0.962, p < 0.001) and HV1.2 (r = 0.995, p < 0.001). The relative coefficients of repeatability were 15 % (SUVmean), 17 % (SUVmax) and 17 % (TBRmax). Voxel-wise analysis of the spatial uptake pattern within the tumors provided an average correlation of 0.65 ± 0.14.

CONCLUSION

Repeated hypoxia PET scans with [(18)F]HX4 provide reproducible and spatially stable results in patients with head and neck cancer and patients with lung cancer. [(18)F]HX4 PET imaging can be used to assess the hypoxic status of tumors and has the potential to aid hypoxia-targeted treatments.

Clostridium to treat cancer: dream or reality?

In their paper "Intratumoral injection of Clostridium novyi-NT spores induces antitumor responses", Roberts et al. describe the induction of antitumor responses following local spore administration of an attenuated C. novyi strain (C. novyi-NT). Stereotactic intratumoral spore injection led to significant survival advantages in a murine orthotopic brain model and local bacterial treatment produced robust responses in a set of spontaneous canine soft tissue carcinomas. Their preclinical findings in both models, provided the basis for a phase 1 investigational clinical study in patients with solid tumors that were either refractory to standard treatment or without an available standard treatment available (NCT01924689). The results of the first patient enrolled in this trial, a 53-year-old female with a retroperitoneal leiomyosarcoma, are described. Next to the non-armed C. novyi-NT described in this paper, very potent genetically modified Clostridium expressing anti-cancer therapeutic genes are also being developed. Are treatments with these non-pathogenic clostridia a viable alternative cancer treatment?

Hypoxia and Serum deprivation protected MiaPaCa-2 cells from KAI1-induced proliferation inhibition through autophagy pathway activation in solid tumors

PURPOSE

KAI1 closely correlates with pancreatic cancer metastasis. There might be some factors that protect the cells from a proliferation inhibition by KAI1 in the solid tumors' microenvironment. Hypoxia and ischemia are the main characteristics of the microenvironment within solid tumors. Whether they affect the KAI1 inhibitory effects on cell proliferation is still unclear.

METHODS

MiaPaCa-2 human pancreatic cancer cells do not express KAI1 protein. However, after being infected with Ad5-KAI1, they expressed KAI1 protein. We cultured them under hypoxic and serum-free conditions to simulate the solid tumor hypoxic-ischemic microenvironment. The cells were divided into the control, hypoxic, serum-free, and hypoxic with serum-free groups. The proliferation and apoptosis were observed by CCK8 and Annexin V-FITC/PI, respectively. The green fluorescent protein-labeled light chain 3 association with autophagosome membranes was detected by confocal microscopy. The ratio of LC3-II-LC3-I expression level was detected by western blot. Pretreatment of 3-MA was used to inhibit the autophagy. We, then observed whether the hypoxic and serum-free conditions could change the effect of KAI1 on cell survival and whether the pretreatment of 3-MA could inhibit the effect of hypoxic and serum-free conditions on KAI1 function.

RESULTS

Hypoxia and serum-free media effectively reduced the apoptosis and proliferation inhibition caused by KAI1 and was beneficial to the cell survival. 3-MA pretreatment effectively blocked the protective effect of hypoxia and serum-free media on the cells by autophagy block.

CONCLUSIONS

Serum-free media and hypoxia protected the MiaPaCa-2 cells from a KAI1-induced apoptosis and proliferation inhibition via autophagy induction.

Nanodrug delivery in reversing multidrug resistance in cancer cells

Different mechanisms in cancer cells become resistant to one or more chemotherapeutics is known as multidrug resistance (MDR) which hinders chemotherapy efficacy. Potential factors for MDR includes enhanced drug detoxification, decreased drug uptake, increased intracellular nucleophiles levels, enhanced repair of drug induced DNA damage, overexpression of drug transporter such as P-glycoprotein(P-gp), multidrug resistance-associated proteins (MRP1, MRP2), and breast cancer resistance protein (BCRP). Currently nanoassemblies such as polymeric/solid lipid/inorganic/metal nanoparticles, quantum dots, dendrimers, liposomes, micelles has emerged as an innovative, effective, and promising platforms for treatment of drug resistant cancer cells. Nanocarriers have potential to improve drug therapeutic index, ability for multifunctionality, divert ABC-transporter mediated drug efflux mechanism and selective targeting to tumor cells, cancer stem cells, tumor initiating cells, or cancer microenvironment. Selective nanocarrier targeting to tumor overcomes dose-limiting side effects, lack of selectivity, tissue toxicity, limited drug access to tumor tissues, high drug doses, and emergence of multiple drug resistance with conventional or combination chemotherapy. Current review highlights various nanodrug delivery systems to overcome mechanism of MDR by neutralizing, evading, or exploiting the drug efflux pumps and those independent of drug efflux pump mechanism by silencing Bcl-2 and HIF1α gene expressions by siRNA and miRNA, modulating ceramide levels and targeting NF-κB. “Theragnostics” combining a cytotoxic agent, targeting moiety, chemosensitizing agent, and diagnostic imaging aid are highlighted as effective and innovative systems for tumor localization and overcoming MDR. Physical approaches such as combination of drug with thermal/ultrasound/photodynamic therapies to overcome MDR are focused. The review focuses on newer drug delivery systems developed to overcome MDR in cancer cell.

US-guided optical tomography: correlation with clinicopathologic variables in breast cancer

We tested the relationships between total hemoglobin concentration (THC), as measured with ultrasound (US)-guided optical tomography, and clinicopathologic variables in invasive ductal cancers; and we evaluated the clinical significance of THC. Fifty-three patients with 65 invasive ductal carcinomas underwent US-guided biopsy and were scanned with a hand-held probe consisting of a co-registered US transducer and an NIR (near-infrared) imager. The lesion location provided by co-registered US was used to guide optical imaging. Light absorption was measured at two optical wavelengths. From this measurement, tumor angiogenesis was assessed on the basis of calculated THC. We investigated the relationships between maximum THC and clinicopathologic variables (tumor size [≤2 cm or >2 cm], metastasis to lymph node or distant organ, histologic grade, lymphovascular invasion, status of ER, PR, HER2 and Ki-67, and triple negativity). The mean maximum THC in the breast cancers was 223.3 ± 106.3 μmol/L. In univariate analysis, HER2 positivity, tumor size, and Ki-67 positivity showed significant correlations with maximum THC (p < 0.05). In multivariate analysis including tumor size, and ER, PR, HER2, and Ki-67 status, HER2 positivity correlated with maximum THC significantly (p = 0.007, parameter estimate 76.44). Maximum THC correlated with HER2, Ki-67 and tumor size in this group of ductal breast carcinomas. Thus, US-guided diffuse optical tomography (US-DOT) may potentially be used to predict tumor aggressiveness in patients with invasive breast cancers.

Predictive biomarker discovery through the parallel integration of clinical trial and functional genomics datasets

The European Union multi-disciplinary Personalised RNA interference to Enhance the Delivery of Individualised Cytotoxic and Targeted therapeutics (PREDICT) consortium has recently initiated a framework to accelerate the development of predictive biomarkers of individual patient response to anti-cancer agents. The consortium focuses on the identification of reliable predictive biomarkers to approved agents with anti-angiogenic activity for which no reliable predictive biomarkers exist: sunitinib, a multi-targeted tyrosine kinase inhibitor and everolimus, a mammalian target of rapamycin (mTOR) pathway inhibitor. Through the analysis of tumor tissue derived from pre-operative renal cell carcinoma (RCC) clinical trials, the PREDICT consortium will use established and novel methods to integrate comprehensive tumor-derived genomic data with personalized tumor-derived small hairpin RNA and high-throughput small interfering RNA screens to identify and validate functionally important genomic or transcriptomic predictive biomarkers of individual drug response in patients. PREDICT's approach to predictive biomarker discovery differs from conventional associative learning approaches, which can be susceptible to the detection of chance associations that lead to overestimation of true clinical accuracy. These methods will identify molecular pathways important for survival and growth of RCC cells and particular targets suitable for therapeutic development. Importantly, our results may enable individualized treatment of RCC, reducing ineffective therapy in drug-resistant disease, leading to improved quality of life and higher cost efficiency, which in turn should broaden patient access to beneficial therapeutics, thereby enhancing clinical outcome and cancer survival. The consortium will also establish and consolidate a European network providing the technological and clinical platform for large-scale functional genomic biomarker discovery. Here we review our current understanding of molecular mechanisms driving resistance to anti-angiogenesis agents, the current limitations of laboratory and clinical trial strategies and how the PREDICT consortium will endeavor to identify a new generation of predictive biomarkers.

Fluorescence lifetime imaging microscopy of chemotherapy-induced apoptosis resistance in a syngenic mouse tumor model

During cancer therapy with DNA-damaging drug-agents, the development of secondary resistance to apoptosis can be observed. In the search for novel therapeutic approaches that can be used in these cases, we monitored chemotherapy-induced apoptosis resistance in a syngenic mouse tumor model. For this, syngenic murine colorectal carcinoma cells, which stably expressed a FRET-based caspase-3 activity sensor, were introduced into animals to induce peritoneal carcinomatosis or disseminated hepatic metastases. This syngenic system allowed in vitro, in vivo and ex vivo analysis of chemotherapy induced apoptosis induction by optically monitoring the caspase-3 sensor state in the tumor cells. Tumor tissue analysis of 5-FU treated mice showed the selection of 5-FU-induced apoptosis resistant tumor cells. These and chemo-naive fluorescent tumor cells could be re-isolated from treated and untreated mice and propagated in cell culture. Re-exposure to 5-FU and second line treatment modalities in this ex-vivo setting showed that 5-FU induced apoptosis resistance could be alleviated by imatinib mesylate (Gleevec). We thus show that syngenic mouse systems that stably express a FRET-based caspase-3 sensor can be employed to analyse the therapeutic efficiency of apoptosis inducing chemotherapy.

Nonviral nanoscale-based delivery of antisense oligonucleotides targeted to hypoxia-inducible factor 1 alpha enhances the efficacy of chemotherapy in drug-resistant tumor

PURPOSE

To enhance the efficacy of cancer treatment, we propose a complex approach: simultaneous delivery to the tumor of a chemotherapeutic agent and a suppressor of hypoxia-inducible factor 1 alpha (HIF1A).

EXPERIMENTAL DESIGN

The novel complex liposomal drug delivery system was developed and evaluated in vitro and in vivo on nude mice bearing xenografts of multidrug-resistant human ovarian carcinoma. The proposed novel complex drug delivery system consists of liposomes as a nanocarrier, a traditional anticancer drug (doxorubicin) as a cell death inducer, and antisense oligonucleotides targeted to HIF1A mRNA as a suppressor of cellular resistance and angiogenesis.

RESULTS

The system effectively delivers active ingredients into tumor cells, multiplies the cell death signal initiated by doxorubicin, and inhibits cellular defensive mechanisms and angiogenesis by down-regulating BCL2, HSP90, and vascular endothelial growth factor proteins. This, in turn, activates caspases, promotes apoptosis, necrosis, and tumor shrinkage. The proposed novel complex multipronged approach enhances the efficiency of chemotherapy.

CONCLUSIONS

The proposed combination therapy prevents the development of resistance in cancer cells, and thus, increases the efficacy of chemotherapy to an extent that cannot be achieved by individual components applied separately. It could form the foundation for a novel type of cancer therapy based on simultaneous delivery of an anticancer drug and a suppressor of HIF1A.

[18F]EF3 is not superior to [18F]FMISO for PET-based hypoxia evaluation as measured in a rat rhabdomyosarcoma tumour model

PURPOSE

The aim of this investigation was to quantitatively compare the novel positron emission tomography (PET) hypoxia marker 2-(2-nitroimidazol-1-yl)-N-(3[(18)F],3,3-trifluoropropyl)acetamide ([(18)F]EF3) with the reference hypoxia tracer [(18)F]fluoromisonidazole ([(18)F]FMISO).

METHODS

[(18)F]EF3 or [(18)F]FMISO was injected every 2 days into two separate groups of rats bearing syngeneic rhabdomyosarcoma tumours. In vivo PET analysis was done by drawing regions of interest on the images of selected tissues. The resulting activity data were quantified by the percentage of injected radioactivity per gram tissue (%ID/g) and tumour to blood (T/B) ratio. The spatial distribution of radioactivity was defined by autoradiography on frozen tumour sections.

RESULTS

The blood clearance of [(18)F]EF3 was faster than that of [(18)F]FMISO. The clearance of both tracers was slower in tumour tissue compared with other tissues. This results in increasing T/B ratios as a function of time post tracer injection (p.i.). The maximal [(18)F]EF3 tumour uptake, compared to the maximum [(18)F]FMISO uptake, was significantly lower at 2 h p.i. but reached similar levels at 4 h p.i. The tumour uptake for both tracers was independent of the tumour volume for all investigated time points. Both tracers showed heterogeneous intra-tumoural distribution.

CONCLUSIONS

[(18)F]EF3 tumour uptake reached similar levels at 4 h p.i. compared with tumour retention observed after injection of [(18)F]FMISO at 2 h p.i. Although [(18)F]EF3 is a promising non-invasive tracer, it is not superior over [(18)F]FMISO for the visualisation of tumour hypoxia. No significant differences between [(18)F]EF3 and [(18)F]FMISO were observed with regard to the intra-tumoural distribution and the extra-tumoural tissue retention.

Plasminogen structural domains exhibit different functions when associated with cell surface GRP78 or the voltage-dependent anion channel

Both the voltage-dependent anion channel and the glucose-regulated protein 78 have been identified as plasminogen kringle 5 receptors on endothelial cells. In this study, we demonstrate that kringle 5 binds to a region localized in the N-terminal domain of the glucose-regulated protein 78, whereas microplasminogen does so through the C-terminal domain of the glucose-regulated protein 78. Both plasminogen fragments induce Ca(2+) signaling cascades; however, kringle 5 acts through voltage-dependent anion channel and microplasminogen does so via the glucose-regulated protein 78. Because trafficking of voltage-dependent anion channel to the cell surface is associated with heat shock proteins, we investigated a possible association between voltage-dependent anion channel and glucose-regulated protein 78 on the surface of 1-LN human prostate tumor cells. We demonstrate that these proteins co-localize, and changes in the expression of the glucoseregulated protein 78 affect the expression of voltage-dependent anion channel. To differentiate the functions of these receptor proteins, either when acting singly or as a complex, we employed human hexokinase I as a specific ligand for voltage-dependent anion channel, in addition to kringle 5. We show that kringle 5 inhibits 1-LN cell proliferation and promotes caspase-7 activity by a mechanism that requires binding to cell surface voltage-dependent anion channel and is inhibited by human hexokinase I.

Phosphorylation of eIF2alpha is required for mRNA translation inhibition and survival during moderate hypoxia

BACKGROUND AND PURPOSE

Human tumors are characterized by temporal fluctuations in oxygen tension. The biological pathways that respond to the dynamic tumor microenvironment represent potential molecular targets for cancer therapy. Anoxic conditions result in eIF2alpha dependent inhibition of overall mRNA translation, differential gene expression, hypoxia tolerance and tumor growth. The signaling pathway which governs eIF2alpha phosphorylation has therefore emerged as a potential molecular target. In this study, we investigated the role of eIF2alpha in regulating mRNA translation and hypoxia tolerance during moderate hypoxia. Since other molecular pathways that regulate protein synthesis are frequently mutated in cancer, we also assessed mRNA translation in a panel of cell lines from different origins.

MATERIALS AND METHODS

Immortalized human fibroblast, transformed mouse embryo fibroblasts (MEFs) and cells from six cancer cell lines were exposed to 0.2% or 0.0% oxygen. We assayed global mRNA translation efficiency by polysome analysis, as well as proliferation and clonogenic survival. The role of eIF2alpha was assessed in MEFs harboring a homozygous inactivating mutation (S51A) as well as in U373-MG cells overexpressing GADD34 (C-term) under a tetracycline-dependent promoter. The involvement of eIF4E regulation was investigated in HeLa cells stably expressing a short hairpin RNA (shRNA) targeting 4E-BP1.

RESULTS

All cells investigated inhibited mRNA translation severely in response to anoxia and modestly in response to hypoxia. Two independent genetic cell models demonstrated that inhibition of mRNA translation in response to moderate hypoxia was dependent on eIF2alpha phosphorylation. Disruption of eIF2alpha phosphorylation caused sensitivity to hypoxia and anoxia.

CONCLUSIONS

Disruption of eIF2alpha phosphorylation is a potential target for hypoxia-directed molecular cancer therapy.

Critical Role for Mitochondrial Oxidative Phosphorylation in the Activation of Tumor Suppressors Bax and Bak

BACKGROUND

Activation of Bax and Bak, which act to permeabilize the mitochondrial membrane, is an essential step in the cell death response and therefore in the suppression of tumorigenesis. However, the mechanisms that regulate activation are poorly understood.

METHODS

Bax and Bak activation (conformational change and dimerization) was monitored in Rat-1 fibroblasts and human cancer cells subjected to endoplasmic reticulum (ER) stress, DNA damage, or tumor necrosis factor-alpha (TNF-alpha) treatment. Pharmacologic inhibitors of reactive oxygen species production, electron transport in the respiratory chain, oxidative phosphorylation, and appropriate controls were used to identify potential modes by which Bax and Bak activation and the cell death response are controlled. The oligomerization state of Bax and Bak was determined by cross-linking and subsequent immunoblot analysis; Bax conformational change was analyzed by immunoprecipitation and immunoblotting with an antibody specific for the active conformation. Cell death was evaluated by dye exclusion.

RESULTS

In both fibroblasts and human cancer cells subjected to cell death stimuli, inhibition of oxidative phosphorylation by use of antimycin A or oligomycin prevented ER stress-, DNA damage-, and TNF-alpha-induced Bax and Bak activation and cell death (UV-induced Rat-1 cell death at 15 hours: control, mean = 33.6%, 95% confidence interval [CI] = 18.8% to 48.4%; antimycin A, mean = 10.0%, 95% CI = 0% to 21.7%; oligomycin, mean = 13.1%, 95% CI = 5.7% to 20.5%; tunicamycin-induced MCF-7 cell death at 9 hours: control, mean = 29.2%, 95% CI = 21.6% to 36.8%; antimycin A, mean = 15.3%, 95% CI = 0.8% to 29.8%; oligomycin, mean = 11.5%, 95% CI = 3.9% to 19.1%; TNF-alpha-induced MCF-7 cell death at 6 hours: control, mean = 24.0%, 95% CI = 12.6% to 35.4%; antimycin A, mean = 8.9%, 95% CI = 3.9% to 13.9%; oligomycin, mean = 13.3%, 95% CI = 10.4% to 16.2%). Increasing and decreasing glycolytic adenosine triphosphate production, by adding glucose and 2-deoxy-D-glucose to the cell growth medium, respectively, neither reversed nor recapitulated, respectively, the effect of compromised oxidative phosphorylation on Bax and Bak activation.

CONCLUSION

Oxidative phosphorylation is required for the activation of Bax and Bak and cell death triggered by disparate death stimuli. The reliance of tumor cells on glycolysis in preference to oxidative phosphorylation even under normoxic conditions (Warburg effect) may therefore be a potential means by which these cells evade programmed cell death.

Clostridium spores as anti-tumour agents

The successful treatment of cancer remains a huge challenge. Consequently, efforts are being made to develop alternative methods of tumour therapy. One of these is the use of live Clostridium species, based on the observation that obligatory anaerobic bacteria specifically colonize the hypoxic and necrotic regions that are present in solid tumours but normally absent in other parts of the body. Although past results have fuelled scepticism about its clinical use, recent promising findings emphasize the potential of Clostridium-directed tumour therapy. These recent developments are reviewed and the reintroduction of this tumour-targeting protein delivery system into clinical settings is discussed.

The tumor microenvironment in the post-PAGET era

The research area of tumor microenvironment is considered, at present, to be an important factor in tumorigenesis and especially in tumor progression. The present mini review is focused on three principles characterizing the nature of the tumor microenvironment. We first discuss the regulatory functions of the tumor microenvironment and the complexity of the combinatorial signaling pathways operating in it. We then address the aspect that the tumor microenvironment incorporates both pro and anti malignancy factors and that a balance between these factors regulates tumor progression. Thirdly we provide evidence that the non-tumor cells in the tumor microenvironment and their products may be different from those of their counterparts residing in non-tumor microenvironments. The conclusion of this mini review is that the tumor microenvironment, by exerting regulatory functions and selective pressures drives cancer cells into one of several molecular evolution pathways thereby determining and shaping their malignancy phenotype.

Effect of hypoxia on Ad5 infection, transgene expression and replication

Oxygen deprivation (hypoxia) is a common feature of various human maladies, including cardiovascular diseases and cancer; however, the effect of hypoxia on Ad-based gene therapies has not been described. In this study, we evaluated how hypoxia (1% pO(2)) affects different aspects of Ad-based therapies, including attachment and uptake, transgene expression, and replication, in a series of cancer cell lines and primary normal cells. We found that hypoxia had no significant effect on the expression or function of the Ad5 attachment (Coxsackievirus and Adenovirus Receptor) and internalization (alpha(v) integrins) proteins, nor on the human cytomegalovirus-driven expression of an exogenous gene carried by a replication-incompetent Ad. Viral replication, however, was compromised by hypoxic conditions. Our studies revealed hypoxia-induced reductions in E1A levels that were mediated at the post-transcriptional level. E1A drives cells into the viral replication optimal S phase of the cell cycle; consequently, the combination of reduced E1A protein and hypoxia-induced G1 arrest of cells may be responsible for the lack of efficient viral replication under hypoxic conditions. Consequently, while traditional replication-incompetent Ad-based vectors appear to be viable delivery systems for hypoxia-associated disease indications, our studies suggest that Oncolytic Ads may need additional factors to efficiently treat hypoxic regions of human tumors.

Does heterogeneity of pimonidazole labelling correspond to the heterogeneity of radiation-response of FaDu human squamous cell carcinoma?

BACKGROUND AND PURPOSE

Pimonidazole is a marker for hypoxic cells which are radioresistant and thereby important for the outcome of radiotherapy. The present study evaluates heterogeneity in pimonidazole binding within and between tumours and relates the results to the heterogeneity of radiation response in the same tumour cell line.

MATERIALS AND METHODS

FaDu, a poorly differentiated human squamous cell carcinoma line, was transplanted subcutaneously into the right hind-leg of NMRI nude mice. Tumours were irradiated with graded single doses either under ambient or clamped blood flow conditions and local tumour control was evaluated after 120 days. Complete dose-response curves for local tumour control were generated and the slope, a measure of heterogeneity of radiation response, was determined. In parallel, 12 unirradiated tumours were examined histologically. Seven serial 10 microm cross-sections per tumour were evaluated using fluorescence microscopy and computerised image analysis to determine the pimonidazole hypoxic fraction (pHF). Heterogeneity in pHF was quantified by its coefficient of variation (CV). Poisson-based model calculations considering the intertumoural heterogeneity of pHF were performed and the slopes of the predicted and the observed dose-response curves were compared.

RESULTS

The mean pHF was 11% [CV 50%] when one central section per tumour was evaluated. Measurements of multiple sections per tumour resulted in a mean pHF of 12% [CV 46%] (P=0.7). Intertumoural heterogeneity in pHF was more pronounced than heterogeneity in individual tumours by a factor of 2. Model calculations based on the variability in pHF resulted in similar slopes of the dose-response curve for local tumour control in comparison with the observed slope when the heterogeneity in an unknown and arbitrarily chosen additional radiobiologically relevant parameter, in this example clonogen density, was taken into account.

CONCLUSIONS

While the average pimonidazole hypoxic fraction in FaDu tumours corresponds well to the radiobiological hypoxic fraction, the variability of pHF in FaDu tumours was not sufficient to explain the heterogeneity of radiation response in the same tumour line. Information on at least one additional parameter is expected to substantially enhance the predictive power of histological markers of tumour hypoxia.

Hypoxic cell turnover in different solid tumor lines

PURPOSE

Most solid tumors contain hypoxic cells, and the amount of tumor hypoxia has been shown to have a negative impact on the outcome of radiotherapy. The efficacy of combined modality treatments depends both on the sequence and timing of the treatments. Hypoxic cell turnover in tumors may be important for optimal scheduling of combined modality treatments, especially when hypoxic cell targeting is involved.

METHODS AND MATERIALS

Previously we have shown that a double bioreductive hypoxic marker assay could be used to detect changes of tumor hypoxia in relation to the tumor vasculature after carbogen and hydralazine treatments. This assay was used in the current study to establish the turnover rate of hypoxic cells in three different tumor models. The first hypoxic marker, pimonidazole, was administered at variable times before tumor harvest, and the second hypoxic marker, CCI-103F, was injected at a fixed time before harvest. Hypoxic cell turnover was defined as loss of pimonidazole (first marker) relative to CCI-103F (second marker).

RESULTS

The half-life of hypoxic cell turnover was 17 h in the murine C38 colon carcinoma line, 23 h and 49 h in the human xenograft lines MEC82 and SCCNij3, respectively. Within 24 h, loss of pimonidazole-stained areas in C38 and MEC82 occurred concurrent with the appearance of pimonidazole positive cell debris in necrotic regions. In C38 and MEC82, most of the hypoxic cells had disappeared after 48 h, whereas in SCCNij3, viable cells that had been labeled with pimonidazole were still observed after 5 days.

CONCLUSIONS

The present study demonstrates that the double hypoxia marker assay can be used to study changes in both the proportion of hypoxic tumor cells and their lifespan at the same time. The present study shows that large differences in hypoxic cell turnover rates may exist among tumor lines, with half-lives ranging from 17-49 h.

Hypoxia inducible factor pathways as targets for functional foods

The etiology of most chronic angiogenic diseases such as rheumatoid arthritis, atherosclerosis, diabetes complications, and cancer includes the presence of pockets of hypoxic cells growing behind aerobic cells and away from blood vessels. Hypoxic cells are the result of uncontrolled growth and insufficient vascularization and have undergone a shift from aerobic to anaerobic metabolism. Cells respond to hypoxia by stimulating the expression of hypoxia inducible factor (HIF), which is critical for survival under hypoxic conditions and in embryogenesis. HIF is a heterodimer consisting of the O2-regulated subunit, HIF-1alpha, and the constitutively expressed aryl hydrocarbon receptor nuclear translocator, HIF-1beta. Under hypoxic conditions, HIF-1alpha is stable, accumulates, and migrates to the nucleus where it binds to HIF-1beta to form the complex (HIF-1alpha + HIF-1beta). Transcription is initiated by the binding of the complex (HIF-1alpha + HIF-1beta) to hypoxia responsive elements (HREs). The complex [(HIF-1alpha + HIF-1beta) + HREs] stimulates the expression of genes involved in angiogenesis, anaerobic metabolism, vascular permeability, and inflammation. Experimental and clinical evidence show that these hypoxic cells are the most aggressive and difficult angiogenic disease cells to treat and are a major reason for antiangiogenic and conventional treatment failure. Hypoxia occurs in early stages of disease development (before metastasis), activates angiogenesis, and stimulates vascular remodeling. HIF-1alpha has also been identified under aerobic conditions in certain types of cancer. This review summarizes the role of hypoxia in some chronic degenerative angiogenic diseases and discusses potential functional foods to target the HIF-1alpha pathways under hypoxic and normoxic conditions. It is reported that dietary quinones, semiquinones, phenolics, vitamins, amino acids, isoprenoids, and vasoactive compounds can down-regulate the HIF-1 pathways and therefore the expression of several proangiogenic factors. Considering the lack of efficiency or the side effects of synthetic antiangiogenic drugs at clinical trials, down-regulation of hypoxia-induced angiogenesis by use of naturally occurring functional foods may provide an effective means of prevention.

Modeling the effect of tumor size in early breast cancer

SUMMARY BACKGROUND DATA

The purpose of this study was to determine the type of relationship between tumor size and mortality in early breast carcinoma.

METHODS

The data was abstracted from 83,686 cases registered in the Surveillance, Epidemiology, and End Results Program of women diagnosed with primary breast carcinoma between 1988 and 1997 presenting with a T1-T2 lesion and no metastasis in whom axillary node dissection was performed: 58,070 women were node-negative (N0) and 25,616 were node-positive (N+). End point was death from any cause. Tumor size was modeled as a continuous variable by proportional hazards using a generalized additive models procedure.

RESULTS

Functionally, a Gompertzian expression exp(-exp(-(size-15)/10)) provided a good fit to the effect of tumor size (in millimeters) on mortality, irrespective of nodal status. Quantitatively, for tumor size between 3 and 50 mm, the increase of crude cumulative death rate (number of observed deaths divided by the number of patients at risk) increased with size from 10% to 25% for N0 and from 20% to 40% for N+.

CONCLUSIONS

The functional relationship of tumor size with mortality is concordant with current knowledge of tumor growth. However, its qualitative and quantitative independence of nodal status is in contradiction with the prevailing concept of sequential disease progression from primary tumor to regional nodes. This argues against the perception that nodal metastases are caused by the primary tumor.

Evaluation of hypoxia in an experimental rat tumour model by [(18)F]fluoromisonidazole PET and immunohistochemistry

This study aimed to evaluate tumour hypoxia by comparing [¹⁸F]Fluoromisonidazole uptake measured using positron emission tomography ([¹⁸F]FMISO-PET) with immunohistochemical (IHC) staining techniques. Syngeneic rhabdomyosarcoma (R1) tumour pieces were transplanted subcutaneously in the flanks of WAG/Rij rats. Tumours were analysed at volumes between 0.9 and 7.3 cm³. Hypoxic volumes were defined using a 3D region of interest on 2 h postinjection [¹⁸F]FMISO-PET images, applying different thresholds (1.2–3.0). Monoclonal antibodies to pimonidazole (PIMO) and carbonic anhydrase IX (CA IX), exogenous and endogenous markers of hypoxia, respectively, were used for IHC staining. Marker-positive fractions were microscopically measured for each tumour, and hypoxic volumes were calculated. A heterogeneous distribution of hypoxia was observed both with histology and [¹⁸F]FMISO autoradiography. A statistically significant correlation (P<0.05) was obtained between the hypoxic volumes defined with [¹⁸F]FMISO-PET and the volumes derived from the PIMO-stained tumour sections (r=0.9066; P=0.0001), regardless of the selected threshold between 1.4 and 2.2. A similar observation was made with the CA IX staining (r=0.8636; P=0.0006). The relationship found between [¹⁸F]FMISO-PET and PIMO- and additionally CA IX-derived hypoxic volumes in rat rhabdomyosarcomas indicates the value of the noninvasive imaging method to measure hypoxia in whole tumours.

Counteraction of pRb-dependent protection after extreme hypoxia by elevated ribonucleotide reductase

We have studied hypoxia-induced cell cycle arrest in human cells where the retinoblastoma tumour suppressor protein (pRb) is either functional (T-47D and T-47DHU-res cells) or abrogated by expression of the HPV18 E7 oncoprotein (NHIK 3025 cells). We have previously found that pRb is dephosphorylated and rebound in the nucleus in T-47D cells arrested in S-phase during hypoxia and that this binding is protracted even following re-oxygenation. In the present study, however, we show that the long-lasting arrest following re-oxygenation induced by pRb-binding in the cell nuclei may be overruled by an elevated level of ribonucleotide reductase (RNR). This seems to create a forced DNA-synthesis, uncoordinated with cell division, which induces endoreduplication of the DNA. The data indicate that the cells initiating endoreduplication continue DNA-synthesis until all DNA is replicated once and then may start cycling and cell division with a doubled DNA-content. Corresponding data on the pRb-incompetent NHIK 3025-cells show similar endoreduplication in these. Thus, the data indicate that endoreduplication of DNA following re-oxygenation may come, either as a result of hypoxic arrest of DNA-synthesis when pRb-function is absent in the cells, or if it is overruled by increased RNR. The present study further shows that pRb not only protects the culture by arresting most of the cells that are exposed to extreme hypoxia in S-phase, but also increases cell survival by means of increased clonogenic ability of these cells. Interestingly, however, cells having an elevated level of RNR have equally high survival as wild-type cells following 20 h extreme hypoxia. If RNR-overruling of pRb-mediated arrest following re-oxygenation results in an unstable genome, this may therefore represent a danger of oncogenic selection as the protective effect of pRb on cell survival seems to be maintained.

Activating transcription factor 4 is translationally regulated by hypoxic stress

Hypoxic stress results in a rapid and sustained inhibition of protein synthesis that is at least partially mediated by eukaryotic initiation factor 2alpha (eIF2alpha) phosphorylation by the endoplasmic reticulum (ER) kinase PERK. Here we show through microarray analysis of polysome-bound RNA in aerobic and hypoxic HeLa cells that a subset of transcripts are preferentially translated during hypoxia, including activating transcription factor 4 (ATF4), an important mediator of the unfolded protein response. Changes in mRNA translation during the unfolded protein response are mediated by PERK phosphorylation of the translation initiation factor eIF2alpha at Ser-51. Similarly, PERK is activated and is responsible for translational regulation under hypoxic conditions, while inducing the translation of ATF4. The overexpression of a C-terminal fragment of GADD34 that constitutively dephosphorylates eIF2alpha was able to attenuate the phosphorylation of eIF2alpha and severely inhibit the induction of ATF4 in response to hypoxic stress. These studies demonstrate the essential role of ATF4 in the response to hypoxic stress, define the pathway for its induction, and reveal that GADD34, a target of ATF4 activation, negatively regulates the eIF2alpha-mediated inhibition of translation. Taken with the concomitant induction of additional ER-resident proteins identified by our microarray analysis, this study suggests an important integrated response between ER signaling and the cellular adaptation to hypoxic stress.

Elevated expression of TGF-beta1 in head and neck cancer-associated fibroblasts

Head and neck cancers are characterized by a vigorous desmoplastic response, but the contribution of stromal-derived growth factors to the tumor microenvironment is poorly understood. We evaluated the expression of stromal growth factor expression in head and neck squamous cell carcinoma (HNSCC) in normal and tumor-associated stromal cells. Stromal tissue was isolated from epithelial cells with laser capture microdissection (LCMD) and analyzed by cDNA array for the expression of TGFalpha, TGF-beta1, HGF, PDGF-alpha, IGFII, bFGF, aFGF, VEGFC, and VEGF. Primary fibroblasts were isolated in vitro from HNSCC tumors, adjacent histologically normal mucosa, and skin in vitro. Fibroblast populations were assessed for TGF-beta1 expression by ELISA and luciferase reporter assay to assess protein expression. We identified TGF-beta1 and IGFII overexpression in normal and tumor-associated stromal cells; however, only TGF-beta1 was significantly overexpressed (3.4-fold) in tumor-associated stroma. Assessment of carcinoma-associated fibroblasts (CAFs), normal dermal fibroblasts (NDFs), and normal mucosal fibroblasts (NMFs) in propagated fibroblasts demonstrated persistently elevated levels of TGF-beta1 in CAFs compared to NMF and NDF populations. Elevated levels of TGF-beta1 were identified in the stromal compartment of HNSCC tumors compared to normal mucosa by immunohistochemical analysis. These results suggest that TGF-beta1 mRNA and protein is specifically upregulated in CAFs in vitro and in vivo.

Up-regulation of the redox mediators thioredoxin and apurinic/apyrimidinic excision (APE)/Ref-1 in hypoxic microregions of invasive cervical carcinomas, mapped using multispectral, wide-field fluorescence image analysis

Thioredoxin and apurinic/apyrimidinic excision (APE)/ref-1 are important redox mediators in biochemical pathways that promote cell survival under adverse conditions including hypoxia and oxidative stress. For example, elevated levels occur surrounding vascular infarcts and protect from reperfusion injury. Because elevated thioredoxin or APE/ref-1 is also associated with resistance to certain forms of cancer treatment, we examined their tissue distribution in a series of 110 cervical carcinoma biopsies. Analysis was done using a quadruple fluorescence imaging technique, incorporating carbonic anhydrase IX (CAIX) immunofluorescence to outline hypoxic microregions and 4',6-diamidino-2-phenylindole to localize nuclear staining of thioredoxin and APE/ref-1. A scanning autostage was used to image the entire tissue section. Thioredoxin and APE/ref-1 levels were expressed as the average pixel brightness in tumor tissue, subdivided based on CAIX and 4',6-diamidino-2-phenylindole staining. Results showed that the nuclear and cytoplasmic levels of thioredoxin were similar, whereas APE/ref-1 expression was greater in nuclei. Neither of these markers was predictive of outcome in this series of patients treated with radical radiotherapy. Both proteins showed highly significant elevations in CAIX-positive regions compared to CAIX-negative regions, and there was a nonsignificant trend for this effect to be greater in adenocarcinomas compared to squamous cell carcinomas. Levels of APE/ref-1 decreased with increasing tumor grade, but the expression was similar in CAIX-positive regions of poorly differentiated tumors compared to moderately or well-differentiated tumors. Elevated expression of thioredoxin and APE/ref-1 might promote cancer cell survival in hypoxic microenvironments of cervical carcinomas.

Recent advances in light ion radiation therapy

BACKGROUND

The fast development of energy- and intensity-modulated radiation therapy during the last two decades using photon and electron beams has when implemented resulted in a considerable improvement of radiation therapy, particularly if combined with radiobiologically based treatment optimization techniques. This has made intensity-modulated electron and photon beams as powerful as today's uniform dose proton therapy. To be able to cure also the most advanced hypoxic and radiation-resistant tumors of complex local spread, intensity-modulated light ion beams are really the ultimate tool and in clinical practice 2 to 3 times less expensive per patient treated than proton therapy. This development and the recent development of advanced tumor diagnostics based on PET-CT imaging of the tumor cell density open the field for new powerful radiobiologically based treatment optimization methods. The ultimate step is to use the unique radiobiologic and dose distributional advantages of light ion beams for truly optimized bioeffect planning where the integral three-dimensional dose delivery and tumor cell survival can be monitored by PET-CT imaging and corrected by biologically based adaptive therapy optimization methods.

PURPOSE

The main purpose of the present paper is to discuss the principal areas of development of therapy optimization, by considering the therapy chain from tumor diagnostics and the use of three-dimensional predictive assay to biologically based treatment optimization with special focus on the rapid clinical development of advanced light ion therapy.

METHODS

Besides the "classical" approaches using low ionization density hydrogen ions (protons, but also possibly deuterons and tritium nuclei) and high ionization density carbon ions, two new approaches will be discussed. In the first one, lithium or beryllium or boron ions, which induce the least detrimental biologic effect to normal tissues for a given biologic effect in a small volume of the tumor, will be key particles. In the second approach, referred patients will be given a high-dose, high-precision "boost" treatment with carbon or oxygen ions during 1 week preceding the final treatment with conventional radiation in the referring hospital. The rationale behind these approaches is to minimize the high ionization density dose to the normal-tissue stroma outside but sometimes also inside the tumor bed and to ensure a more uniform and optimal biologic effectiveness in the tumor, also on the microscopic scale. The present discussion indicates that BIologically Optimized predictive Assay based light ion Radiation Therapy (Bio-Art) is really the ultimate way to perform high-precision radiation therapy using checkpoints of the integral dose delivery and the tumor response and, based on this information, perform compensating corrections of the dose delivery. By using biologically optimized scanned high-energy photon or ion beams, it is possible to measure in vivo the three-dimensional dose delivery using the same PET-CT camera that was used for diagnosing the tumor spread. This method thus opens up the door for truly three-dimensional biologically optimized adaptive radiation therapy, where the measured dose delivery to the true target tissues can be used to fine-adjust the incoming beams, so that possible errors in the integral therapy process are eliminated toward the end of the treatment. Interestingly enough, practically all major error sources--such as organ motion, treatment planning errors, patient setup errors, and dose delivery problems due to gantry, multileaf, or scanning beam errors--can be corrected for in this way.

RESULTS AND CONCLUSIONS

Radiobiologically optimized dose delivery using intensity and radiation quality modulation based on high-resolution PET-CT or Magnetic Resonance Spectroscopic Imaging (MRSI)-based tumor and normal-tissue imaging is probably the ultimate development of radiation therapy, taking the unique physical and biologic advantages of light ions fully into account in truly patient-individualized curative treatment schedules. Using recently available biologically based treatment ilable biologically based treatment optimization algorithms, it is possible to improve the treatment outcome for advanced tumors by as much as 10-40%. The adaptive radiotherapy process based both on three-dimensional tumor cell survival and dose delivery monitoring has the potential of percent accuracy in tumor response and dose delivery monitoring, using two-dimensional, narrow high-energy photon beam scanning and three-dimensional (11)C Bragg peak scanning for radiation quality and intensity-modulated dose delivery. There is no doubt that the future of radiation therapy is very promising, and gradually more and more patients may not even need advanced surgery. Instead, they could be cured by biologically optimized electron, photon, or light ion therapy, where the densely ionizing Bragg peak is placed solely in the gross tumor, and a lower ionization density is used in microscopically invasive tumor volumes.

Autocrine laminin-5 ligates alpha6beta4 integrin and activates RAC and NFkappaB to mediate anchorage-independent survival of mammary tumors

Invasive carcinomas survive and evade apoptosis despite the absence of an exogenous basement membrane. How epithelial tumors acquire anchorage independence for survival remains poorly defined. Epithelial tumors often secrete abundant amounts of the extracellular matrix protein laminin 5 (LM-5) and frequently express alpha6beta4 integrin. Here, we show that autocrine LM-5 mediates anchorage-independent survival in breast tumors through ligation of a wild-type, but not a cytoplasmic tail-truncated alpha6beta4 integrin. alpha6beta4 integrin does not mediate tumor survival through activation of ERK or AKT. Instead, the cytoplasmic tail of beta4 integrin is necessary for basal and epidermal growth factor-induced RAC activity, and RAC mediates tumor survival. Indeed, a constitutively active RAC sustains the viability of mammary tumors lacking functional beta1 and beta4 integrin through activation of NFkappaB, and overexpression of NFkappaB p65 mediates anchorage-independent survival of nonmalignant mammary epithelial cells. Therefore, epithelial tumors could survive in the absence of exogenous basement membrane through autocrine LM-5-alpha6beta4 integrin-RAC-NFkappaB signaling.

Molecular basis of angiogenesis and cancer

Angiogenesis is a term that describes the formation of new capillaries from a pre-existing vasculature. This process is very important in physiologic conditions because it helps healing injured tissues, and in female populations it helps forming the placenta after fertilization and reconstructs the inside layer of the uterus after menstruation. Angiogenesis is the result of an intricate balance between proangiogenic and antiangiogenic factors and is now very well recognized as a powerful control point in tumor development. In this particular environment, the fine modulation among proangiogenic and antiangiogenic factors is disrupted, leading to inappropriate vessels growth. In this review, we discuss the molecular basis of angiogenesis during tumor growth and we also illustrate some of the molecules that are involved in this angiogenic switch.