Incorporating cancer stem cells in radiation therapy treatment response modeling and the implication in glioblastoma multiforme treatment resistance

An efficient rectangular optimization method for sparse orthogonal collimator based small animal irradiation

Objective.Intensity-modulated radiotherapy (IMRT) is widely used in clinical radiotherapy, treating varying malignancies with conformal doses. As the test field for clinical translation, preclinical small animal experiments need to mimic the human radiotherapy condition, including IMRT. However, small animal IMRT is a systematic challenge due to the lack of corresponding hardware and software for miniaturized targets.Approach.The sparse orthogonal collimators (SOC) based on the direct rectangular aperture optimization (RAO) substantially simplified the hardware for miniaturization. This study investigates and evaluates a significantly improved RAO algorithm for complex mouse irradiation using SOC. Because the Kronecker product representation of the rectangular aperture is the main limitation of the computational performance, we reformulated matrix multiplication in the data fidelity term using multiplication with small matrices instead of the Kronecker product of the dose loading matrices. Solving the optimization problem was further accelerated using the Fast Iterative Shrinkage-Thresholding Algorithm (FISTA).Main results.Four mouse cases, including a liver, a brain tumor, a concave U-target, and a complex total marrow irradiation (TMI) case, were included in this study with manually delineated targets and OARs. Seven coplanar-field SOC IMRT (sIMRT) plans were compared with idealistic fluence map based IMRT (iIMRT) plans. For the first three cases with simpler and smaller targets, the differences between sIMRT plans and iIMRT plans in the planning target volumes (PTV) statistics are within 1%. For the TMI case, the sIMRT plans are superior in reducing hot spots (also termedDmax) of PTV, kidneys, lungs, heart, and bowel by 20.5%, 31.5%, 24.67%, 20.13%, and 17.78%, respectively. On average, in four cases in this study, the sIMRT plan conformity is comparable to that of the iIMRT's with lightly increased R50 and Integral Dose by 2.23% and 2.78%.Significance.The significantly improved sIMRT optimization method allows fast plan creation in under 1 min for smaller targets and makes complex TMI planning feasible while achieving comparable dosimetry to idealistic IMRT with fluence map optimization.

Stereotactic Body Radiotherapy and Conventional Radiotherapy Induce Cytoskeleton Extension and Enlargement of Cell Morphology in Non-Small Cell Lung Cancer

Stereotactic body radiotherapy (SBRT) is now widely used in cancer therapy. However, the biological effects of SBRT compared with conventional radiotherapy (CRT) are not clear. The cytoskeleton plays an important role in many biological processes and cellular life activities. The effects of SBRT or CRT on the morphology and cytoskeletal structure of non-small cell lung cancer (NSCLC) cells remain unknown. Based on the biologically equivalent dose (BED) formula, we designed SBRT and CRT fractionation regimens with the same BED. The morphology was captured during radiation, and rhodamine-phalloidin immunofluorescence was used to study the cytoskeleton. A lactate dehydrogenase assay kit was used to determine the cell membrane permeability, and western blot was used to detect the cytoskeleton protein expression levels. The morphology and cytoskeleton expanded after SBRT or CRT, with an increase in cell membrane permeability and stable cytoskeleton protein levels. Besides, different dose of SBRT (10,20,30 Gy) induce similar morphology and cytoskeleton enlargement. Our findings indicate that SBRT and CRT can induce cytoskeleton reorganization and the enlargement of cell morphology (at different rates) in NSCLC. The morphology and cytoskeleton enlargement after SBRT are dose independence.

Treating Glioblastoma Multiforme (GBM) with super hyperfractionated radiation therapy: Implication of temporal dose fractionation optimization including cancer stem cell dynamics

PURPOSE

A previously developed ordinary differential equation (ODE) that models the dynamic interaction and distinct radiosensitivity between cancer stem cells (CSC) and differentiated cancer cells (DCC) was used to explain the definitive treatment failure in Glioblastoma Multiforme (GBM) for conventionally and hypo-fractionated treatments. In this study, optimization of temporal dose modulation based on the ODE equation is performed to explore the feasibility of improving GBM treatment outcome.

METHODS

A non-convex optimization problem with the objective of minimizing the total cancer cell number while maintaining the normal tissue biological effective dose (BEDnormal) at 100 Gy, equivalent to the conventional 2 Gy × 30 dosing scheme was formulated. With specified total number of dose fractions and treatment duration, the optimization was performed using a paired simulated annealing algorithm with fractional doses delivered to the CSC and DCC compartments and time intervals between fractions as variables. The recurrence time, defined as the time point at which the total tumor cell number regrows to 2.8×109 cells, was used to evaluate optimization outcome. Optimization was performed for conventional treatment time frames equivalent to currently and historically utilized fractionation schemes, in which limited improvement in recurrence time delay was observed. The efficacy of a super hyperfractionated approach with a prolonged treatment duration of one year was therefore tested, with both fixed regular and optimized variable time intervals between dose fractions corresponding to total number of fractions equivalent to weekly, bi-weekly, and monthly deliveries (n = 53, 27, 13). Optimization corresponding to BEDnormal of 150 Gy was also obtained to evaluate the possibility in further recurrence delay with dose escalation.

RESULTS

For the super hyperfractionated schedules with dose fraction number equivalent to weekly, bi-weekly, and monthly deliveries, the recurrence time points were found to be 430.5, 423.9, and 413.3 days, respectively, significantly delayed compared with the recurrence time of 250.3 days from conventional fractionation. Results show that optimal outcome was achieved by first delivering infrequent fractions followed by dense once per day fractions in the middle and end of the treatment course, with sparse and low dose treatments in the between. The dose to the CSC compartment was held relatively constant throughout while larger dose fractions to the DCC compartment were observed in the beginning and final fractions that preceded large time intervals. Dose escalation to BEDnormal of 150 Gy was shown capable of further delaying recurrence time to 452 days.

CONCLUSION

The development and utilization of a temporal dose fractionation optimization framework in the context of CSC dynamics have demonstrated that substantial delay in GBM local tumor recurrence could be achieved with a super hyperfractionated treatment approach. Preclinical and clinical studies are needed to validate the efficacy of this novel treatment delivery method.

The small molecule drug CBL0137 increases the level of DNA damage and the efficacy of radiotherapy for glioblastoma

Glioblastoma (GBM) is an incurable brain tumor with inevitable recurrence. This is in part due to a highly malignant cancer stem cell (CSC) subpopulation of tumor cells that is particularly resistant to conventional treatments, including radiotherapy. Here we show that CBL0137, a small molecule anti-cancer agent, sensitizes GBM CSCs to radiotherapy. CBL0137 sequesters the FACT (facilitates chromatin transcription) complex to chromatin, resulting in cytotoxicity preferentially within tumor cells. We show that when combined with radiotherapy, CBL0137 inhibited GBM CSC growth and resulted in more DNA damage in the CSCs compared to irradiation or drug alone. Using an in vivo subcutaneous model, we showed that the frequency of GBM CSCs was reduced when tumors were pretreated with CBL0137 and then exposed to irradiation. Survival studies with orthotopic GBM models resulted in significantly extended survival for mice treated with combinatorial therapy. As GBM CSCs contribute to the inevitable recurrence in patients, targeting them is imperative. This work establishes a new treatment paradigm for GBM that sensitizes CSCs to irradiation and may ultimately reduce tumor recurrence.

cPLA2α reversibly regulates different subsets of cancer stem cells transformation in cervical cancer

Cervical cancer stem cells (CCSCs) are considered major causes of chemoresistance/radioresistance and metastasis. Although several cell surface antigens have been identified in CCSCs, these markers vary among tumors because of CSC heterogeneity. However, whether these markers specifically distinguish CCSCs with different functions is unclear. Here, we demonstrated that CCSCs exist in two biologically distinct phenotypes characterized by different levels of cytosolic phospholipase A2α (cPLA2α) expression. Overexpression of cPLA2α results in a CD44⁺ CD24^- phenotype associated with mesenchymal traits, including increased invasive and migration abilities, whereas CCSCs with cPLA2α downregulation express CD133 and show quiescent epithelial characteristics. In addition, cPLA2α regulates the reversible transition between mesenchymal and epithelial CCSC states through PKCζ, an atypical protein kinase C, which governs cancer cell state changes and the maintenance of various embryonic stem cell characteristics, further inhibiting β-catenin-E-cadherin interaction in membrane and promoting β-catenin translocation into the nucleus to affect the transcriptional regulation of stemness signals. We propose that reversible transitions between mesenchymal and epithelial CCSC states regulated by cPLA2α are necessary for cervical cancer metastasis and recurrence. Thus, cPLA2α might be an attractive therapeutic target for eradicating different states of CCSCs to eliminate tumors more effectively.

A sparse orthogonal collimator for small animal intensity-modulated radiation therapy. Part II: hardware development and commissioning

PURPOSE

A dose-modulation device for small animal radiotherapy is required to use clinically analogous treatment techniques, which will likely increase the translatability of preclinical research results. Because the clinically used multileaf collimator (MLC) is impractical for miniaturization, we have developed a simpler, better-suited sparse orthogonal collimator (SOC) for delivering small animal intensity-modulated radiation therapy (IMRT) using a rectangular aperture optimization (RAO) treatment planning system.

METHODS

The SOC system was modeled in computer-aided design software and fabricated with machined tungsten leaves and three-dimensional (3D) printed leaf housing. A graphical user interface was developed for controlling and calibrating the SOC leaves, which are driven by Arduino-controlled stepper motors. A Winston-Lutz test was performed to assess mechanical alignment, and abutting field and grid dose patterns were created to analyze intra- and intercalibration leaf positioning error. Leaf transmission and penumbra were measured over the full range of gantry angles and leaf positions, respectively. Three SOC test plans were delivered, and film measurements were compared to the intended dose distributions. The differences in maximum, mean, and minimum, as well as pixelwise absolute dose differences, were compared for each structure, and a gamma analysis was performed for the target structures using criteria of 4% dose difference and 0.3 mm distance to agreement.

RESULTS

The Winston-Lutz test revealed maximum directional offsets between the SOC and primary collimator axes of 0.53 mm at 0° and 0.68 mm over the full 360°. Upper and lower abutting field patterns had maximum dose deviations of 18.8 ± 3.1% and 15.5 ± 2.9%, respectively, and grid patterns showed intra- and intercalibration repeatability of 93% and 91%, respectively. Extremely low midleaf (0.15 ± 0.05%) and interleaf (0.27 ± 0.22%) transmission was measured, with no significant rotational variation. The average penumbra was ~0.8 mm for all leaves at field center, with a range of 0.17 mm for all leaf positions. A highly concave test plan was delivered with a ~ 95% gamma analysis pass rate, and a realistic mouse phantom liver irradiation plan achieved a pass rate of ~98%. A highly complex dose distribution was also created with 551 SOC apertures averaging 2.4 mm in size.

CONCLUSIONS

A sparse orthogonal collimator was developed and commissioned, with promising preliminary dosimetry results. The SOC design, with its limited moving components and high dose-modulation resolution, is ideal for delivering high-quality small animal IMRT with our RAO-based treatment planning system.

Implementation of the Chick Chorioallantoic Membrane (CAM) Model in Radiation Biology and Experimental Radiation Oncology Research

Radiotherapy (RT) is part of standard cancer treatment. Innovations in treatment planning and increased precision in dose delivery have significantly improved the therapeutic gain of radiotherapy but are reaching their limits due to biologic constraints. Thus, a better understanding of the complex local and systemic responses to RT and of the biological mechanisms causing treatment success or failure is required if we aim to define novel targets for biological therapy optimization. Moreover, optimal treatment schedules and prognostic biomarkers have to be defined for assigning patients to the best treatment option. The complexity of the tumor environment and of the radiation response requires extensive in vivo experiments for the validation of such treatments. So far in vivo investigations have mostly been performed in time- and cost-intensive murine models. Here we propose the implementation of the chick chorioallantoic membrane (CAM) model as a fast, cost-efficient model for semi high-throughput preclinical in vivo screening of the modulation of the radiation effects by molecularly targeted drugs. This review provides a comprehensive overview on the application spectrum, advantages and limitations of the CAM assay and summarizes current knowledge of its applicability for cancer research with special focus on research in radiation biology and experimental radiation oncology.

Modeling the effect of intratumoral heterogeneity of radiosensitivity on tumor response over the course of fractionated radiation therapy

Background

Standard radiobiology theory of radiation response assumes a uniform innate radiosensitivity of tumors. However, experimental data show that there is significant intratumoral heterogeneity of radiosensitivity. Therefore, a model with heterogeneity was developed and tested using existing experimental data to show the potential effects from the presence of an intratumoral distribution of radiosensitivity on radiation therapy response over a protracted radiation therapy treatment course.

Methods

The standard radiation response curve was modified to account for a distribution of radiosensitivity, and for variations in the repopulation rates of the tumor cell subpopulations. Experimental data from the literature were incorporated to determine the boundaries of the model. The proposed model was then used to show the changes in radiosensitivity of the tumor during treatment, and the effects of fraction size, α/β ratio and variation of the repopulation rates of tumor cells.

Results

In the presence of an intratumoral distribution of radiosensitivity, there is rapid selection of radiation-resistant cells over a course of fractionated radiation therapy. Standard treatment fractionation regimes result in the near-complete replacement of the initial population of sensitive cells with a population of more resistant cells. Further, as treatment progresses, the tumor becomes more resistant to further radiation treatment, making each fractional dose less efficacious. A wider initial distribution induces increased radiation resistance. Hypofractionation is more efficient in a heterogeneous tumor, with increased cell kill for biologically equivalent doses, while inducing less resistance. The model also shows that a higher growth rate in resistant cells can account for the accelerated repopulation that is seen during the clinical treatment of patients.

Conclusions

Modeling of tumor cell survival with radiosensitivity heterogeneity alters the predicted tumor response, and explains the induction of radiation resistance by radiation treatment, the development of accelerated repopulation, and the potential beneficial effects of hypofractionation. Tumor response to treatment may be better predicted by assaying for the distribution of radiosensitivity, or the extreme of the radiosensitivity, rather than measuring the initial, general radiation sensitivity of the untreated tumor.

Oxidative stress levels and dynamic changes in mitochondrial gene expression in a radiation-induced lung injury model

The purpose of this study was to set up a beagle dog model, for radiation-induced lung injury, that would be able to supply fresh lung tissues in the different injury phases for research into oxidative stress levels and mitochondrial gene expression. Blood serum and tissues were collected via CT-guided core needle biopsies from dogs in the various phases of the radiation response over a 40-week period. Levels of reactive oxygen species (ROS) and manganese superoxide dismutase 2 (MnSOD) protein expression in radiation-induced lung injury were determined by in situ immunocytochemistry; malondialdehyde (MDA) content and reductase activity in the peripheral blood were also tested; in addition, the copy number of the mitochondrial DNA and the level of function of the respiratory chain in the lung tissues were assessed. ROS showed dynamic changes and peaked at 4 weeks; MnSOD was mainly expressed in the Type II alveolar epithelium at 8 weeks; the MDA content and reductase activity in the peripheral blood presented no changes; the copy numbers of most mitochondrial genes peaked at 8 weeks, similarly to the level of function of the corresponding respiratory chain complexes; the level of function of the respiratory chain complex III did not peak until 24 weeks, similarly to the level of function of the corresponding gene Cytb. Radiation-induced lung injury was found to be a dynamically changing process, mainly related to interactions between local ROS, and it was not associated with the levels of oxidative stress in the peripheral blood. Mitochondrial genes and their corresponding respiratory chain complexes were found to be involved in the overall process.

Kinetic modeling of tumor regression incorporating the concept of cancer stem-like cells for patients with locally advanced lung cancer

Background

Personalized medicine for patients receiving radiation therapy remains an elusive goal due, in part, to the limits in our understanding of the underlying mechanisms governing tumor response to radiation. The purpose of this study was to develop a kinetic model, in the context of locally advanced lung cancer, connecting cancer cell subpopulations with tumor volumes measured during the course of radiation treatment for understanding treatment outcome for individual patients.

Methods

The kinetic model consists of three cell compartments: cancer stem-like cells (CSCs), non-stem tumor cells (TCs) and dead cells (DCs). A set of ordinary differential equations were developed to describe the time evolution of each compartment, and the analytic solution of these equations was iterated to be aligned with the day-to-day tumor volume changes during the course of radiation treatment. A least squares fitting method was used to estimate the parameters of the model that include the proportion of CSCs and their radio-sensitivities. This model was applied to five patients with stage III lung cancer, and tumor volumes were measured from 33 cone-beam computed tomography (CBCT) images for each of these patients. The analytical solution of these differential equations was compared with numerically simulated results.

Results

For the five patients with late stage lung cancer, the derived proportions of CSCs are 0.3 on average, the average probability of the symmetry division is 0.057 and the average surviving fractions of CSCs is 0.967, respectively. The derived parameters are comparable to the results from literature and our experiments. The preliminary results suggest that the CSC self-renewal rate is relatively small, compared to the proportion of CSCs for locally advanced lung cancers.

Conclusions

A novel mathematical model has been developed to connect the population of cancer stem-like cells with tumor volumes measured from a sequence of CBCT images. This model may help improve our understanding of tumor response to radiation therapy, and is valuable for development of new treatment regimens for patients with locally advanced lung cancer.

Definitive re-irradiation using intensity-modulated radiation therapy in cancers of the head and neck, focusing on rare tumors

PURPOSE

To analyze the outcomes following re-irradiation for local recurrence of rare head and neck tumors.

MATERIAL AND METHODS

We retrospectively analyzed 11 patients who had received intensity-modulated radiation therapy (IMRT) for recurrent tumors in the head and neck except for laryngopharynx.

RESULTS

Primary tumor sites included the maxillary sinus, nasal cavity, and external ear canal in six, three, and two patients, respectively. The median follow-up times were 13 (range, 3-54) months. The median survival time was 17 months with 1- and 2-year survival rates of 63.64 and 39.77%, respectively. Among 11 patients, five experienced local failure in the follow-up period. The 1- and 2-year local control rates were 58 and 47%, respectively. Patients who had received a radiation dose of ≥3 Gy per fraction showed significantly better local control than those receiving less (p = .0419). One patient experienced Grade 3 facial pain as acute toxicity. Late toxicities included radiographic findings of partial central nervous system necrosis in three patients and Grade 3 osteonecrosis and Grade 3 facial nerve disorder in one patient.

CONCLUSIONS

Re-irradiation of rare head and neck tumors using IMRT for loco-regional recurrence may be an acceptable treatment option.

Radioresistance of the breast tumor is highly correlated to its level of cancer stem cell and its clinical implication for breast irradiation

BACKGROUND AND PURPOSE

Growing evidence suggested the coexistence of cancer stem cells (CSCs) within solid tumors. We aimed to study radiosensitivity parameters for the CSCs and differentiated tumor cells (TCs) and the correlation of the fractions of CSCs to the overall tumor radioresistance.

MATERIAL AND METHODS

Surviving fractions of breast cancer cell lines were analyzed using a dual-compartment Linear-quadratic model with independent fitting parameters: radiosensitive α_TC, β_TC, α_CSC, β_CSC, and fraction of CSCs f. The overall tumor radio-resistance, the biological effective doses and tumor control probability were estimated as a function of CSC fraction for different fractionation regimens. The pooled clinical outcome data were fitted to the single- and dual-compartment linear-quadric models.

RESULTS

CSCs were more radioresistant characterized by smaller α compared to TCs: α_TC=0.1±0.2, α_CSC=0.04±0.07 for MCF-7 (f=0.1%), α_TC=0.08±0.25, α_CSC=0.04±0.18 for SUM159PT (f=2.46%). Higher f values were correlated with increasing radioresistance in cell lines. Analysis of clinical outcome data is in accordance of a dual-compartment CSC model prediction. Higher percentage of BCSCs resulted in more overall tumor radioresistance and less biological effectiveness.

CONCLUSIONS

Percentage of CSCs strongly correlated to overall tumor radioresistance. This observation suggested potential individualized radiotherapy to account for heterogeneous population of CSCs and their distinct radiosensitivity for breast cancer.

A radiobiological model of radiotherapy response and its correlation with prognostic imaging variables

Radiobiological models of tumour control probability (TCP) can be personalized using imaging data. We propose an extension to a voxel-level radiobiological TCP model in order to describe patient-specific differences and intra-tumour heterogeneity. In the proposed model, tumour shrinkage is described by means of a novel kinetic Monte Carlo method for inter-voxel cell migration and tumour deformation. The model captures the spatiotemporal evolution of the tumour at the voxel level, and is designed to take imaging data as input. To test the performance of the model, three image-derived variables found to be predictive of outcome in the literature have been identified and calculated using the model's own parameters. Simulating multiple tumours with different initial conditions makes it possible to perform an in silico study of the correlation of these variables with the dose for 50% tumour control ([Formula: see text]) calculated by the model. We find that the three simulated variables correlate with the calculated [Formula: see text]. In addition, we find that different variables have different levels of sensitivity to the spatial distribution of hypoxia within the tumour, as well as to the dynamics of the migration mechanism. Finally, based on our results, we observe that an adequate combination of the variables may potentially result in higher predictive power.

The Role of Lymphocytes in Radiotherapy-Induced Adverse Late Effects in the Lung

Radiation-induced pneumonitis and fibrosis are dose-limiting side effects of thoracic irradiation. Thoracic irradiation triggers acute and chronic environmental lung changes that are shaped by the damage response of resident cells, by the resulting reaction of the immune system, and by repair processes. Although considerable progress has been made during the last decade in defining involved effector cells and soluble mediators, the network of pathophysiological events and the cellular cross talk linking acute tissue damage to chronic inflammation and fibrosis still require further definition. Infiltration of cells from the innate and adaptive immune systems is a common response of normal tissues to ionizing radiation. Herein, lymphocytes represent a versatile and wide-ranged group of cells of the immune system that can react under specific conditions in various ways and participate in modulating the lung environment by adopting pro-inflammatory, anti-inflammatory, or even pro- or anti-fibrotic phenotypes. The present review provides an overview on published data about the role of lymphocytes in radiation-induced lung disease and related damage-associated pulmonary diseases with a focus on T lymphocytes and B lymphocytes. We also discuss the suspected dual role of specific lymphocyte subsets during the pneumonitic phase and fibrotic phase that is shaped by the environmental conditions as well as the interaction and the intercellular cross talk between cells from the innate and adaptive immune systems and (damaged) resident epithelial cells and stromal cells (e.g., endothelial cells, mesenchymal stem cells, and fibroblasts). Finally, we highlight potential therapeutic targets suited to counteract pathological lymphocyte responses to prevent or treat radiation-induced lung disease.

Fast and high temperature hyperthermia coupled with radiotherapy as a possible new treatment for glioblastoma

Background

A new transcranial focused ultrasound device has been developed that can induce hyperthermia in a large tissue volume. The purpose of this work is to investigate theoretically how glioblastoma multiforme (GBM) can be effectively treated by combining the fast hyperthermia generated by this focused ultrasound device with external beam radiotherapy.

Methods/Design

To investigate the effect of tumor growth, we have developed a mathematical description of GBM proliferation and diffusion in the context of reaction–diffusion theory. In addition, we have formulated equations describing the impact of radiotherapy and heat on GBM in the reaction–diffusion equation, including tumor regrowth by stem cells. This formulation has been used to predict the effectiveness of the combination treatment for a realistic focused ultrasound heating scenario.

Our results show that patient survival could be significantly improved by this combined treatment modality.

Discussion

High priority should be given to experiments to validate the therapeutic benefit predicted by our model.

Electronic supplementary material

The online version of this article (doi:10.1186/s40349-016-0078-3) contains supplementary material, which is available to authorized users.

Chloroquine, an autophagy inhibitor, potentiates the radiosensitivity of glioma initiating cells by inhibiting autophagy and activating apoptosis

Background

Glioblastoma is refractory to conventional treatment, which is combined of surgery, chemotherapy and radiotherapy. Recent studies have shown that glioma initiating cells (GICs) contribute to tumorigenesis and radioresistance. Recently, other studies showed that the GICs use the autophagy as the major pathway to survive. Chloroquine, an anti-malarial chemical, is an autophagic inhibitor which blocks autophagosome fusion with lysosome and slows down lysosomal acidification. The aim of this study was to explore the mechanisms of chloroquine on the radiosensitivity of GICs.

Methods

Human glioblastoma cell lines U87 were investigated. MTT and clonogenic survival assay were used to evaluate the cell viability and survival from radiation. The formation of autophagosomes were evaluated by immunofluorescence. Annexin V-FITC/PI staining and flow cytometry were used to quantify the apoptotic cells. The expression levels of proteins were analyzed by Western blot. Cell cycle status was analyzed by checking DNA content after staining with PI. A comet assay was used to assess the DNA repair in the cells. Tumorsphere assay was used for evaluating GICs’ renewal ability.

Results

Treatment of U87 GICs with chloroquine (10–80 nmol/L) alone inhibited the cell growth in a dose-dependent manner. A dose of chloroquine (20 nmol/L) obviously enhanced the radiation sensitivity of U87 GICs., we found more punctate patterns of microtubule-associated protein LC3 immunoreactivity in radiation-treated U87 GICs, and the level of membrane-bound LC3-II was obviously enhanced. A combination of radiation and chloroquine obviously enhanced the U87 GICs’ apoptosis, as demonstrated by the enhanced levels of caspase-3, and reduced level of Bcl-2. In additon, combination of radiation and chloroquine cause G1/G0 cell cycle arrest. what’s more, Chloroquine obviously weakened the repair of radiation-induced DNA damage as reflected by the tail length of the comet. Combination treatment of irradiation and chloroquine has synergistic effects on decreasing the GICs’ tumorsphere number and diameter.

Conclusion

Chloroquine enhances the radiosensitivity of GICs in vitro, suggesting the feasibility of joint treatment with chloroquine with radiation for GBM.

Targeting stem cells by radiation: From the biological angle to clinical aspects

Radiotherapy is a cornerstone of anticancer treatment. However in spite of technical evolutions, important rates of failure and of toxicity are still reported. Although numerous pre-clinical data have been published, we address the subject of radiotherapy-stem cells interaction from the clinical efficacy and toxicity perspective. On one side, cancer stem cells (CSCs) have been recently evidenced in most of solid tumor primary locations and are thought to drive radio-resistance phenomena. It is particularly suggested in glioblastoma, where CSCs were showed to be housed in the subventricular zone (SVZ). In recent retrospective studies, the radiation dose to SVZ was identified as an independent factor significantly influencing overall survival. On the other side, healthy tissue stem cells radio-destruction has been recently suggested to cause two of the most quality of life-impacting side effects of radiotherapy, namely memory disorders after brain radiotherapy, and xerostomia after head and neck radiotherapy. Recent publications studying the impact of a radiation dose decrease on healthy brain and salivary stem cells niches suggested significantly reduced long term toxicities. Stem cells comprehension should be a high priority for radiation oncologists, as this particular cell population seems able to widely modulate the efficacy/toxicity ratio of radiotherapy in real life patients.

Optimal treatment and stochastic modeling of heterogeneous tumors

In this work we review past articles that have mathematically studied cancer heterogeneity and the impact of this heterogeneity on the structure of optimal therapy. We look at past works on modeling how heterogeneous tumors respond to radiotherapy, and take a particularly close look at how the optimal radiotherapy schedule is modified by the presence of heterogeneity. In addition, we review past works on the study of optimal chemotherapy when dealing with heterogeneous tumors.

REVIEWERS

This article was reviewed by Thomas McDonald, David Axelrod, and Leonid Hanin.

Current Stem Cell Biomarkers and Their Functional Mechanisms in Prostate Cancer

Currently there is little effective treatment available for castration resistant prostate cancer, which is responsible for the majority of prostate cancer related deaths. Emerging evidence suggested that cancer stem cells might play an important role in resistance to traditional cancer therapies, and the studies of cancer stem cells (including specific isolation and targeting on those cells) might benefit the discovery of novel treatment of prostate cancer, especially castration resistant disease. In this review, we summarized major biomarkers for prostate cancer stem cells, as well as their functional mechanisms and potential application in clinical diagnosis and treatment of patients.

Mathematical Modeling of the Role of Survivin on Dedifferentiation and Radioresistance in Cancer

We use a mathematical model to investigate cancer resistance to radiation, based on dedifferentiation of non-stem cancer cells into cancer stem cells. Experimental studies by Iwasa 2008, using human non-small cell lung cancer (NSCLC) cell lines in mice, have implicated the inhibitor of apoptosis protein survivin in cancer resistance to radiation. A marked increase in radio-sensitivity was observed, after inhibiting survivin expression with a specific survivin inhibitor YM155 (sepantronium bromide). It was suggested that these observations are due to survivin-dependent dedifferentiation of non-stem cancer cells into cancer stem cells. Here, we confirm this hypothesis with a mathematical model, which we fit to Iwasa's data on NSCLC in mice. We investigate the timing of combination therapies of YM155 administration and radiation. We find an interesting dichotomy. Sometimes it is best to hit a cancer with a large radiation dose right at the beginning of the YM155 treatment, while in other cases, it appears advantageous to wait a few days until most cancer cells are sensitized and then radiate. The optimal strategy depends on the nature of the cancer and the dose of radiation administered.

Therapeutic interactions of autophagy with radiation and temozolomide in glioblastoma: evidence and issues to resolve

Glioblastoma is a unique model of non-metastasising disease that kills the vast majority of patients through local growth, despite surgery and local irradiation. Glioblastoma cells are resistant to apoptotic stimuli, and their death occurs through autophagy. This review aims to critically present our knowledge regarding the autophagic response of glioblastoma cells to radiation and temozolomide (TMZ) and to delineate eventual research directions to follow, in the quest of improving the curability of this incurable, as yet, disease. Radiation and TMZ interfere with the autophagic machinery, but whether cell response is driven to autophagy flux acceleration or blockage is disputable and may depend on both cell individuality and radiotherapy fractionation or TMZ schedules. Potent agents that block autophagy at an early phase of initiation or at a late phase of autolysosomal fusion are available aside to agents that induce functional autophagy, or even demethylating agents that may unblock the function of autophagy-initiating genes in a subset of tumours. All these create a maze, which if properly investigated can open new insights for the application of novel radio- and chemosensitising policies, exploiting the autophagic pathways that glioblastomas use to escape death.