Targeting the heat shock response in combination with radiotherapy: Sensitizing cancer cells to irradiation-induced cell death and heating up their immunogenicity

Harnessing multifunctional collagen mimetic peptides to create bioinspired stimuli responsive hydrogels for controlled cell culture

The demand for synthetic soft materials with bioinspired structures continues to grow. Material applications range from in vitro and in vivo tissue mimics to therapeutic delivery systems, where well-defined synthetic building blocks offer precise and reproducible property control. This work examines a synthetic assembling peptide, specifically a multifunctional collagen mimetic peptide (mfCMP) either alone or with reactive macromers, for the creation of responsive hydrogels that capture aspects of soft collagen-rich tissues. We first explored how buffer choice impacts mfCMP hierarchical assembly, in particular, peptide melting temperature, fibril morphology, and ability to form physical hydrogels. Assembly in physiologically relevant buffer resulted in collagen-like fibrillar structures and physically assembled hydrogels with shear-thinning (as indicated through strain-yielding) and self-healing properties. Further, we aimed to create fully synthetic, composite peptide-polymer hydrogels with dynamic responses to various stimuli, inspired by the extracellular matrix (ECM). Specifically, we established mfCMP-poly(ethylene glycol) (PEG) hydrogel compositions that demonstrate increasing non-linear viscoelasticity in response to applied strain as the amount of assembled mfCMP content increases. Furthermore, the thermal responsiveness of mfCMP physical crosslinks was harnessed to manipulate the composite hydrogel mechanical properties in response to changes in temperature. Finally, cells relevant in wound healing, human lung fibroblasts, were encapsulated within these peptide-polymer hydrogels to explore the impact of increased mfCMP, and the resulting changes in viscoelasticity, on cell response. This work establishes mfCMP building blocks as versatile tools for creating hybrid and adaptable systems with applications ranging from injectable shear-thinning materials to responsive interfaces and synthetic ECMs for tissue engineering.

Machine learning-based analysis of cancer cell-derived vesicular proteins revealed significant tumor-specificity and predictive potential of extracellular vesicles for cell invasion and proliferation - A meta-analysis

BACKGROUND

Although interest in the role of extracellular vesicles (EV) in oncology is growing, not all potential aspects have been investigated. In this meta-analysis, data regarding (i) the EV proteome and (ii) the invasion and proliferation capacity of the NCI-60 tumor cell lines (60 cell lines from nine different tumor types) were analyzed using machine learning methods.

METHODS

On the basis of the entire proteome or the proteins shared by all EV samples, 60 cell lines were classified into the nine tumor types using multiple logistic regression. Then, utilizing the Least Absolute Shrinkage and Selection Operator, we constructed a discriminative protein panel, upon which the samples were reclassified and pathway analyses were performed. These panels were validated using clinical data (n = 4,665) from Human Protein Atlas.

RESULTS

Classification models based on the entire proteome, shared proteins, and discriminative protein panel were able to distinguish the nine tumor types with 49.15%, 69.10%, and 91.68% accuracy, respectively. Invasion and proliferation capacity of the 60 cell lines were predicted with R2 = 0.68 and R2 = 0.62 (p < 0.0001). The results of the Reactome pathway analysis of the discriminative protein panel suggest that the molecular content of EVs might be indicative of tumor-specific biological processes.

CONCLUSION

Integrating in vitro EV proteomic data, cell physiological characteristics, and clinical data of various tumor types illuminates the diagnostic, prognostic, and therapeutic potential of EVs. Video Abstract.

Using immunotherapy to enhance the response of a C3H mammary carcinoma to proton radiation

BACKGROUND

The benefit of combining immunotherapy with photon irradiation has been shown pre-clinically and clinically. This current pre-clinical study was designed to investigate the anti-tumour action of combining immunotherapy with protons.

MATERIALS AND METHODS

Male CDF1 mice, with a C3H mammary carcinoma inoculated on the right rear foot, were locally irradiated with single radiation doses when tumours reached 200mm3. Radiation was delivered with an 83-107MeV pencil scanning proton beam in the centre of a 3 cm spread out Bragg peak. Following irradiation (day 0), mice were injected intraperitoneal with anti-CTLA-4, anti-PD-1, or anti-PD-L1 (10 mg/kg) twice weekly for two weeks. Endpoints were tumour growth time (TGT3; time to reach 3 times treatment volume) or local tumour control (percent of mice showing tumour control at 90 days). A Student's T-test (tumour growth) or Chi-squared test (tumour control) were used for statistical analysis; significance levels of p < 0.05.

RESULTS

Untreated tumours had a mean (± 1 S.E.) TGT3 of 4.6 days (± 0.4). None of the checkpoint inhibitors changed this TGT3. A linear increase in TGT3 was seen with increasing radiation doses (5-20 Gy), reaching 17.2 days (± 0.7) with 20 Gy. Anti-CTLA-4 had no effect on radiation doses up to 15 Gy, but significantly enhanced 20 Gy; the TGT3 being 23.0 days (± 1.3). Higher radiation doses (35-60 Gy) were investigated using a tumour control assay. Logit analysis of the dose response curve, resulted in a TCD50 value (radiation dose causing 50% tumour control; with 95% confidence intervals) of 48 Gy (44-53) for radiation only. This significantly decreased to 43 Gy (38-49) when mice were treated with anti-CTLA-4. Neither anti-PD-1 nor anti-PD-L1 significantly affected tumour control.

CONCLUSION

Checkpoint inhibitors enhanced the response of this C3H mammary carcinoma to proton irradiation. However, this enhancement depended on the checkpoint inhibitor and radiation dose.

Myoglobin-loaded gadolinium nanotexaphyrins for oxygen synergy and imaging-guided radiosensitization therapy

Gadolinium (Gd3+)-coordinated texaphyrin (Gd-Tex) is a promising radiosensitizer that entered clinical trials, but temporarily fails largely due to insufficient radiosensitization efficacy. Little attention has been given to using nanovesicles to improve its efficacy. Herein, Gd-Tex is transformed into building blocks "Gd-Tex-lipids" to self-assemble nanovesicles called Gd-nanotexaphyrins (Gd-NTs), realizing high density packing of Gd-Tex in a single nanovesicle and achieving high Gd-Tex accumulation in tumors. To elucidate the impact of O2 concentration on Gd-Tex radiosensitization, myoglobin (Mb) is loaded into Gd-NTs (Mb@Gd-NTs), resulting in efficient relief of tumor hypoxia and significant enhancement of Gd-Tex radiosensitization, eventually inducing the obvious long-term antitumor immune memory to inhibit tumor recurrence. In addition to Gd3+, the versatile Mb@Gd-NTs can also chelate 177Lu3+ (Mb@177Lu/Gd-NTs), enabling SPECT/MRI dual-modality imaging for accurately monitoring drug delivery in real-time. This "one-for-all" nanoplatform with the capability of chelating various trivalent metal ions exhibits broad clinical application prospects in imaging-guided radiosensitization therapy.

Natural Products Targeting Hsp90 for a Concurrent Strategy in Glioblastoma and Neurodegeneration

Glioblastoma multiforme (GBM) is one of the most common aggressive, resistant, and invasive primary brain tumors that share neurodegenerative actions, resembling many neurodegenerative diseases. Although multiple conventional approaches, including chemoradiation, are more frequent in GBM therapy, these approaches are ineffective in extending the mean survival rate and are associated with various side effects, including neurodegeneration. This review proposes an alternative strategy for managing GBM and neurodegeneration by targeting heat shock protein 90 (Hsp90). Hsp90 is a well-known molecular chaperone that plays essential roles in maintaining and stabilizing protein folding to degradation in protein homeostasis and modulates signaling in cancer and neurodegeneration by regulating many client protein substrates. The therapeutic benefits of Hsp90 inhibition are well-known for several malignancies, and recent evidence highlights that Hsp90 inhibitors potentially inhibit the aggressiveness of GBM, increasing the sensitivity of conventional treatment and providing neuroprotection in various neurodegenerative diseases. Herein, the overview of Hsp90 modulation in GBM and neurodegeneration progress has been discussed with a summary of recent outcomes on Hsp90 inhibition in various GBM models and neurodegeneration. Particular emphasis is also given to natural Hsp90 inhibitors that have been evidenced to show dual protection in both GBM and neurodegeneration.

HSP90 promotes radioresistance of cervical cancer cells via reducing FBXO6 mediated CD147 polyubiquitination

HSP90 inhibition might be a promising strategy to overcome the radioresistance of some cancers. In the current study, we further explored the mechanisms of HSP90 in regulating the radiosensitivity of cervical cancer cells. Bioinformatic analysis was performed based on data from TCGA‐CESC. Cellular and molecular studies were conducted using CaSki and SiHa and the derived radioresistant (RR) subclones. Through a proteomics screen, we identified HSP90 chaperones (both HSP90α and HSP90β) as CD147‐binding partners supporting its stabilization. Targeting HSP90 sensitized CaSki‐RR and SiHa‐RR cancer cells to irradiation partially through CD147 destabilization. Mechanistically, HSP90 interacts with FBXO6 and reduces FBXO6‐mediated proteasomal degradation of CD147. Enforced FBXO6 overexpression also sensitized CaSki‐RR and SiHa‐RR cancer cells to irradiation. These effects were enhanced using 17‐AAG treatment but were weakened by CD147 overexpression. Survival analysis further confirmed the association between high FBXO6 expression and favorable progression‐free survival among patients with cervical cancer. In conclusion, this study showed that HSP90 promotes radioresistance of cervical cancer cells partially via reducing FBXO6 mediated CD147 polyubiquitination. These findings help to explain why HSP90 inhibitor exerts radio‐sensitizing effects in cervical cancer.

Abscopal effect in the radio and immunotherapy

This review is devoted to a rare in clinical practice, but promising phenomenon of regression distant non-irradiated metastases in combination therapy of cancer patients. R. H. Mole in 1953 suggested introducing the term "abscopal effect" to denote the effect of ionizing radiation "at a distance from the irradiated volume but within the same organism." Currently, it is a hypothesis in the treatment of metastatic cancer, when there is a regression of untreated areas simultaneously with a decrease in the tumor. After the discovery of immune checkpoint cases were increase with patients treated with check-point blockade (especially lymphocyte associated protein 4, programmed cell death 1/programmed cell death 1 ligand 1) and which have an abscopal effect. This review systematizes works covering the time period from 1969 to 2019, which give cases of the abscopal effect at different localizations. However, abscopal effect is a poorly understood phenomenon. In this review, the authors tried to collect all information about the possible mechanisms of the abscopal effect, possible role in antitumor response and frequency abscopal effect at radio/immunotherapy or combined both.

Prion protein is associated with a worse prognosis of head and neck squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinoma (HNSC) etiopathogenesis remains unclear, and the biological changes with the activation of heat shock proteins (HSPs) and prion protein (PRNP) promoted by hypoxia in HNSC are undetermined. This study investigates hypoxia's effect in lymph node metastasis by PRNP expression changes and its main partners.

METHODS

The study combined a theoretical/cell culture study with a case-control study. First, bioinformatics and cell culture were performed. A case-control study was performed in a second step by comparing HNSC patients with and without lymph node metastasis.

ANALYSES

The Cancer Genome Atlas (TCGA) data source validates the theory in the global population study.

RESULTS

Bioinformatics analysis suggests that hypoxia-inducible factor-1α (HIF1A) is associated with HSPA4, HSP90AA1 and PRNP expression. TCGA data validate the hypothesis that higher HSP90AA1, HSPA4 and PRNP are related to metastases and low survival. Herein, the cell study demonstrated that muted PRNP did not respond to hypoxia.

DISCUSSION

Our results collectively provide the first evidence that PRNP promotes HNSC lymph node metastasis progression through the upregulation of HSPA4, HSP90AA1 and HIF1A. Our findings may provide a molecular basis for the promoting Role of PRNP in HNSC progression.

Inhibition of HSP90 as a Strategy to Radiosensitize Glioblastoma: Targeting the DNA Damage Response and Beyond

Radiotherapy is an essential component of multi-modality treatment of glioblastoma (GBM). However, treatment failure and recurrence are frequent and give rise to the dismal prognosis of this aggressive type of primary brain tumor. A high level of inherent treatment resistance is considered to be the major underlying reason, stemming from constantly activated DNA damage response (DDR) mechanisms as a consequence of oncogene overexpression, persistent replicative stress, and other so far unknown reasons. The molecular chaperone heat shock protein 90 (HSP90) plays an important role in the establishment and maintenance of treatment resistance, since it crucially assists the folding and stabilization of various DDR regulators. Accordingly, inhibition of HSP90 represents a multi-target strategy to interfere with DDR function and to sensitize cancer cells to radiotherapy. Using NW457, a pochoxime-based HSP90 inhibitor with favorable brain pharmacokinetic profile, we show here that HSP90 inhibition at low concentrations with per se limited cytotoxicity leads to downregulation of various DNA damage response factors on the protein level, distinct transcriptomic alterations, impaired DNA damage repair, and reduced clonogenic survival in response to ionizing irradiation in glioblastoma cells in vitro. In vivo, HSP90 inhibition by NW457 improved the therapeutic outcome of fractionated CBCT-based irradiation in an orthotopic, syngeneic GBM mouse model, both in terms of tumor progression and survival. Nevertheless, in view of the promising in vitro results the in vivo efficacy was not as strong as expected, although apart from the radiosensitizing effects HSP90 inhibition also reduced irradiation-induced GBM cell migration and tumor invasiveness. Hence, our findings identify the combination of HSP90 inhibition and radiotherapy in principle as a promising strategy for GBM treatment whose performance needs to be further optimized by improved inhibitor substances, better formulations and/or administration routes, and fine-tuned treatment sequences.

The construction of a lymphoma cell-based, DC-targeted vaccine, and its application in lymphoma prevention and cure

In recent years, Non-Hodgkin lymphoma (NHL) has been one of the most fast-growing malignant tumor diseases. NHL poses severe damages to physical health and a heavy burden to patients. Traditional therapies (chemotherapy or radiotherapy) bring some benefit to patients, but have severe adverse effects and do not prevent relapse. The relevance of emerging immunotherapy options (immune-checkpoint blockers or adoptive cellular methods) for NHL remains uncertain, and more intensive evaluations are needed. In this work, inspired by the idea of vaccination to promote an immune response to destroy tumors, we used a biomaterial-based strategy to improve a tumor cell-based vaccine and constructed a novel vaccine named Man-EG7/CH@CpG with antitumor properties. In this vaccine, natural tumor cells are used as a vector to load CpG-ODN, and following lethal irradiation, the formulations were decorated with mannose. The study of the characterization of the double-improved vaccine evidenced the enhanced ability of DCs targeting and improved immunocompetence, which displayed an antitumor function. In the lymphoma prevention model, the Man-EG7/CH@CpG vaccine restrained tumor formation with high efficiency. Furthermore, unlike the non-improved vaccine, the double-improved vaccine elicited an enhanced antitumor effect in the lymphoma treatment model. Next, to improve the moderate therapeutic effect of the mono-treatment method, we incorporated a chemotherapeutic drug (doxorubicin, DOX) into the process of vaccination and devised a combination regimen. Fortunately, a tumor inhibition rate of ~85% was achieved via the combination therapy, which could not be achieved by mono-chemotherapy or mono-immunotherapy. In summary, the strategy presented here may provide a novel direction in the establishment of a tumor vaccine and is the basis for a prioritization scheme of immuno-chemotherapy in enhancing the therapeutic effect on NHL.

Sequenced Combinations of Cisplatin and Selected Phytochemicals towards Overcoming Drug Resistance in Ovarian Tumour Models

In the present study, cisplatin, artemisinin, and oleanolic acid were evaluated alone, and in combination, on human ovarian A2780, A2780^ZD0473R, and A2780^cisR cancer cell lines, with the aim of overcoming cisplatin resistance and side effects. Cytotoxicity was assessed by MTT reduction assay. Combination index (CI) values were used as a measure of combined drug effect. MALDI TOF/TOF MS/MS and 2-DE gel electrophoresis were used to identify protein biomarkers in ovarian cancer and to evaluate combination effects. Synergism from combinations was dependent on concentration and sequence of administration. Generally, bolus was most synergistic. Moreover, 49 proteins differently expressed by 2 ≥ fold were: CYPA, EIF5A1, Op18, p18, LDHB, P4HB, HSP7C, GRP94, ERp57, mortalin, IMMT, CLIC1, NM23, PSA3,1433Z, and HSP90B were down-regulated, whereas hnRNPA1, hnRNPA2/B1, EF2, GOT1, EF1A1, VIME, BIP, ATP5H, APG2, VINC, KPYM, RAN, PSA7, TPI, PGK1, ACTG and VDAC1 were up-regulated, while TCPA, TCPH, TCPB, PRDX6, EF1G, ATPA, ENOA, PRDX1, MCM7, GBLP, PSAT, Hop, EFTU, PGAM1, SERA and CAH2 were not-expressed in A2780^cisR cells. The proteins were found to play critical roles in cell cycle regulation, metabolism, and biosynthetic processes and drug resistance and detoxification. Results indicate that appropriately sequenced combinations of cisplatin with artemisinin (ART) and oleanolic acid (OA) may provide a means to reduce side effects and circumvent platinum resistance.

Priming of Anti-tumor Immune Mechanisms by Radiotherapy Is Augmented by Inhibition of Heat Shock Protein 90

Radiotherapy is an essential part of multi-modal cancer therapy. Nevertheless, for certain cancer entities such as colorectal cancer (CRC) the indications of radiotherapy are limited due to anatomical peculiarities and high radiosensitivity of the surrounding normal tissue. The development of molecularly targeted, combined modality approaches may help to overcome these limitations. Preferably, such strategies should not only enhance radiation-induced tumor cell killing and the abrogation of tumor cell clonogenicity, but should also support the stimulation of anti-tumor immune mechanisms – a phenomenon which moved into the center of interest of preclinical and clinical research in radiation oncology within the last decade. The present study focuses on inhibition of heat shock protein 90 (HSP90) whose combination with radiotherapy has previously been reported to exhibit convincing therapeutic synergism in different preclinical cancer models. By employing in vitro and in vivo analyses, we examined if this therapeutic synergism also applies to the priming of anti-tumor immune mechanisms in model systems of CRC. Our results indicate that the combination of HSP90 inhibitor treatment and ionizing irradiation induced apoptosis in colorectal cancer cells with accelerated transit into secondary necrosis in a hyperactive Kras-dependent manner. During secondary necrosis, dying cancer cells released different classes of damage-associated molecular patterns (DAMPs) that stimulated migration and recruitment of monocytic cells in vitro and in vivo. Additionally, these dying cancer cell-derived DAMPs enforced the differentiation of a monocyte-derived antigen presenting cell (APC) phenotype which potently triggered the priming of allogeneic T cell responses in vitro. In summary, HSP90 inhibition – apart from its radiosensitizing potential – obviously enables and supports the initial steps of anti-tumor immune priming upon radiotherapy and thus represents a promising partner for combined modality approaches. The therapeutic performance of such strategies requires further in-depth analyses, especially for but not only limited to CRC.

Tumors Resistant to Checkpoint Inhibitors Can Become Sensitive after Treatment with Vascular Disrupting Agents

Immune therapy improves cancer outcomes, yet many patients do not respond. This pre-clinical study investigated whether vascular disrupting agents (VDAs) could convert an immune unresponsive tumor into a responder. CDF1 mice, with 200 mm³ C3H mammary carcinomas in the right rear foot, were intraperitoneally injected with combretastatin A-4 phosphate (CA4P), its A-1 analogue OXi4503, and/or checkpoint inhibitors (anti-PD-1, PD-L1, or CTLA-4 antibodies), administered twice weekly for two weeks. Using the endpoint of tumor growth time (TGT5; time to reach five times the starting volume), we found that none of the checkpoint inhibitors (10 mg/kg) had any effect on TGT5 compared to untreated controls. However, CA4P (100 mg/kg) or OXi4503 (5–50 mg/kg) did significantly increase TGT5. This further significantly increased by combining the VDAs with checkpoint inhibitors, but was dependent on the VDA, drug dose, and inhibitor. For CA4P, a significant increase was found when CA4P (100 mg/kg) was combined with anti-PD-L1, but not with the other two checkpoint inhibitors. With OXi4503 (50 mg/kg), a significant enhancement occurred when combined with anti-PD-L1 or anti-CTLA-4, but not anti-PD-1. We observed no significant improvement with lower OXi4503 doses (5–25 mg/kg) and anti-CTLA-4, although 30% of tumors were controlled at the 25 mg/kg dose. Histological assessment of CD4/CD8 expression actually showed decreased levels up to 10 days after treatment with OXi4503 (50 mg/kg). Thus, the non-immunogenic C3H mammary carcinoma was unresponsive to checkpoint inhibitors, but became responsive in mice treated with VDAs, although the mechanism remains unclear.

Damage-associated molecular patterns in tumor radiotherapy

Radiotherapy is one of the most common modalities for the treatment of cancer. One of the most promising effects of radiotherapy is immunologic cell death and the release of danger alarms, which are known as damage-associated molecular patterns (DAMPs). DAMPs are able to trigger cancer cells and other cells within tumor microenvironment (TME), either for suppression or promotion of tumor growth. Heat shock proteins (HSPs) including HSP70 and HSP90, high mobility group box 1 (HMGB1), and adenosine triphosphate (ATP) and its metabolites such as adenosine are the most common danger alarms that are released after radiotherapy-induced immunologic cell death. Some DAMPs including adenosine is able to interact with both cancer cells as well as other cells in TME to promote tumor growth and resistance to radiotherapy. However, others are able to trigger anti-tumor immunity or both tumor suppressive and immunosuppressive mechanisms depending on affected cells. In this review, we explain the mechanisms behind the release of radiation-induced DAMPs, and its consequences on cells within tumor. Targeting of these mechanisms may be in favor of tumor control in combination with radiotherapy and radioimmunotherapy.

Current Approaches for Combination Therapy of Cancer: The Role of Immunogenic Cell Death

Cell death resistance is a key feature of tumor cells. One of the main anticancer therapies is increasing the susceptibility of cells to death. Cancer cells have developed a capability of tumor immune escape. Hence, restoring the immunogenicity of cancer cells can be suggested as an effective approach against cancer. Accumulating evidence proposes that several anticancer agents provoke the release of danger-associated molecular patterns (DAMPs) that are determinants of immunogenicity and stimulate immunogenic cell death (ICD). It has been suggested that ICD inducers are two different types according to their various activities. Here, we review the well-characterized DAMPs and focus on the different types of ICD inducers and recent combination therapies that can augment the immunogenicity of cancer cells.

3D tumour spheroids for the prediction of the effects of radiation and hyperthermia treatments

For multimodality therapies such as the combination of hyperthermia and radiation, quantification of biological effects is key for dose prescription and response prediction. Tumour spheroids have a microenvironment that more closely resembles that of tumours in vivo and may thus be a superior in vitro cancer model than monolayer cultures. Here, the response of tumour spheroids formed from two established human cancer cell lines (HCT116 and CAL27) to single and combination treatments of radiation (0-20 Gy), and hyperthermia at 47 °C (0-780 CEM43) has been evaluated. Response was analysed in terms of spheroid growth, cell viability and the distribution of live/dead cells. Time-lapse imaging was used to evaluate mechanisms of cell death and cell detachment. It was found that sensitivity to heat in spheroids was significantly less than that seen in monolayer cultures. Spheroids showed different patterns of shrinkage and regrowth when exposed to heat or radiation: heated spheroids shed dead cells within four days of heating and displayed faster growth post-exposure than samples that received radiation or no treatment. Irradiated spheroids maintained a dense structure and exhibited a longer growth delay than spheroids receiving hyperthermia or combination treatment at (thermal) doses that yielded equivalent levels of clonogenic cell survival. We suggest that, unlike radiation, which kills dividing cells, hyperthermia-induced cell death affects cells independent of their proliferation status. This induces microenvironmental changes that promote spheroid growth. In conclusion, 3D tumour spheroid growth studies reveal differences in response to heat and/or radiation that were not apparent in 2D clonogenic assays but that may significantly influence treatment efficacy.

Immune Checkpoint Inhibitors for the Treatment of Unresectable Stage III Non-Small Cell Lung Cancer: Emerging Mechanisms and Perspectives

There has been no improvement in outcome for patients with unresectable locally advanced (stage III) non-small cell lung cancer (NSCLC) for more than 10 years. The standard treatment for these patients is definitive concurrent chemotherapy and radiation (CCRT). Although the goal of treatment in this setting is to achieve a cure, most patients progress and their prognosis is poor, with a 5-year survival rate of 15-30%. There is thus an urgent need for the development of novel anticancer treatments in this patient population. Recent advances in cancer immunotherapy have led to a marked improvement in clinical outcome for advanced NSCLC. Such immunotherapy mainly consists of the administration of immune checkpoint inhibitors (ICIs) such as antibodies to cytotoxic T lymphocyte-associated protein-4 (CTLA-4) or to either programmed cell death-1 (PD-1) or its ligand PD-L1. Durvalumab (MEDI4736) is a high-affinity human immunoglobulin G1 monoclonal antibody that blocks the binding of PD-L1 on tumor cells or antigen-presenting cells to PD-1 on T cells. The PACIFIC study recently evaluated consolidation immunotherapy with durvalumab versus placebo administered after concurrent chemoradiotherapy (CCRT) in patients with unresectable stage III NSCLC. It revealed a significant improvement in both progression-free and overall survival with durvalumab, and this improvement was associated with a favorable safety profile. This achievement has made durvalumab a standard of care for consolidation after CCRT in patients with unresectable stage III NSCLC, and it has now been approved in this setting by regulatory agencies in the United States, Canada, Japan, Australia, Switzerland, Malaysia, Singapore, India, and the United Arab Emirates. In this review, we briefly summarize the results of the PACIFIC trial, including those of post hoc analysis, and we address possible molecular mechanisms, perspectives, and remaining questions related to combined treatment with CCRT and ICIs in this patient population.

Focused Ultrasound-Mediated Hyperthermia in Vitro: An Experimental Arrangement for Treating Cells under Tissue-Mimicking Conditions

An experimental arrangement that allows in vitro exposure of cells to focused ultrasound-mediated hyperthermia (43°C-55°C) in a tissue-mimicking phantom with biological, acoustic and thermal properties comparable to those of human soft tissue is described. Cells were embedded in a compressed collagen gel, which was sandwiched between 6-mm-thick slices of biocompatible, acoustically absorbing and thermally tissue mimicking poly(vinyl alcohol) cryo-gel. To illustrate the system's potential, cells were exposed using a 1.66-MHz focused ultrasound beam (spatial-peak temporal-average intensities (ISPTA) = 900-1400 W/cm2) that traced out a circular trajectory (5-8 mm in diameter). Real-time temperature monitoring allowed cells to be exposed reproducibly to a pre-determined thermal dose. An experimental planning tool that estimates the thermal dose distribution throughout the sample and allows spatial correlation with cell position has been developed. Treatment response was evaluated qualitatively using microscopy and cell viability testing. This experimental arrangement has significant potential for future, biologically relevant, in vitro focused ultrasound-mediated hyperthermia studies.

A cellular automaton model for spheroid response to radiation and hyperthermia treatments

Thermo-radiosensitisation is a promising approach for treatment of radio-resistant tumours such as those containing hypoxic subregions. Response prediction and treatment planning should account for tumour response heterogeneity, e.g. due to microenvironmental factors, and quantification of the biological effects induced. 3D tumour spheroids provide a physiological in vitro model of tumour response and a systems oncology framework for simulating spheroid response to radiation and hyperthermia is presented. Using a cellular automaton model, 3D oxygen diffusion, delivery of radiation and/or hyperthermia were simulated for many ([Formula: see text]) individual cells forming a spheroid. The iterative oxygen diffusion model was compared to an analytical oxygenation model and simulations were calibrated and validated against experimental data for irradiated (0-10 Gy) and/or heated (0-240 CEM43) HCT116 spheroids. Despite comparable clonogenic survival, spheroid growth differed significantly following radiation or hyperthermia. This dynamic response was described well by the simulation ([Formula: see text] > 0.85). Heat-induced cell death was implemented as a fast, proliferation-independent process, allowing reoxygenation and repopulation, whereas radiation was modelled as proliferation-dependent mitotic catastrophe. This framework stands out both through its experimental validation and its novel ability to predict spheroid response to multimodality treatment. It provides a good description of response where biological dose-weighting based on clonogenic survival alone was insufficient.

Cellular Stress Responses in Radiotherapy

Radiotherapy is one of the major cancer treatment strategies. Exposure to penetrating radiation causes cellular stress, directly or indirectly, due to the generation of reactive oxygen species, DNA damage, and subcellular organelle damage and autophagy. These radiation-induced damage responses cooperatively contribute to cancer cell death, but paradoxically, radiotherapy also causes the activation of damage-repair and survival signaling to alleviate radiation-induced cytotoxic effects in a small percentage of cancer cells, and these activations are responsible for tumor radio-resistance. The present study describes the molecular mechanisms responsible for radiation-induced cellular stress response and radioresistance, and the therapeutic approaches used to overcome radioresistance.

Radiotherapy in combination with hyperthermia suppresses lung cancer progression via increased NR4A3 and KLF11 expression

Purpose: Hyperthermia (HT), a clinical treatment involving delivery of heat to tumors, has been used in combination with traditional chemotherapy and radiotherapy to enhance their effects. However, the molecular mechanism underlying the high efficacy of combination therapy is not clear. This study was conducted to identify the molecular mechanism underlying the sensitization of lung cancer to radiotherapy by HT.Materials and methods: Nuclear receptor subfamily 4, group A, member 3 (NR4A3) and Krüppel-like factor 11 (KLF11) expression in non-small-cell lung cancer cells was confirmed by performing real-time quantitative reverse transcription-polymerase chain reaction. Tumor cell proliferation and apoptosis were assessed via a colony-forming assay and Annexin V/propidium iodide staining.Results and conclusions: Expression profile analysis revealed elevated levels of NR4A3 and KLF11 in A549 lung cancer cells after treatment with HT combined with radiation. We also confirmed that NR4A3 and KLF11 induced apoptosis and inhibited cell proliferation by elevating intracellular reactive oxygen species levels. Knockdown of NR4A3 or KLF11 using siRNA led to decreased effects of radiohyperthermia. Finally, the effect of these two factors on lung cancer progression was evaluated by in vivo xenograft studies. Taken together, the results suggest that NR4A3 and KLF11 are critical for increasing the efficacy of radiotherapy in combination with HT.

Surrogates of immunologic cell death (ICD) and chemoradiotherapy outcomes in head and neck squamous cell carcinoma (HNSCC)

OBJECTIVES

Chemoradiation can induce immunogenic (ICD) or tolerogenic cell death. ICD relies on the generation of damage-associated molecular patterns which can stimulate toll-like receptors (TLRs). We sought to determine whether we can predict responses to chemoradiation by measuring surrogate biomarkers of ICD in a cohort of patients with locally advanced (LA) head and neck squamous cell carcinoma (HNSCC).

MATERIALS AND METHODS

In a cohort of 113 LA HNSCC pts we evaluated expression of TLR4, TLR7 and TLR9 in the EpCAM + circulating tumor cell (CTC) fraction at baseline and after cisplatin chemoradiation. We also quantified changes in chemokines CXCL10, CXCL16 and IL-2R in the serum.

RESULTS

Seventy three patients had evaluable specimens. Among cases with biomarker assessment at baseline and post treatment, 36.8% had an increase in CXCL10 levels (p = 0.022), 73.7% had an increase in CXCL16 levels (p = 0.002) and 63.8% had an increase in IL2Ra levels (p = 0.032) with treatment. 52.0% of evaluable cases at baseline and post-treatment had an increase in TLR4 levels (p = 0.996), 42.9% had an increase in TLR7 levels (p = 0.042) and 27.7% had increase in TLR9 levels (p = 0.011) with treatment. CXCL10 levels at baseline were significantly associated with PFS and OS (p = 0.010 and p = 0.032, respectively).

CONCLUSIONS

Our results suggest that chemoradiation leads to quantifiable effects in surrogate markers of ICD. These effects may inform trials combining chemoradiation with immune checkpoint inhibitors. In addition, CXCL10 has prognostic effect in pts treated with chemoradiation.

177Lu-octreotate therapy for neuroendocrine tumours is enhanced by Hsp90 inhibition

177Lu-octreotate is an FDA-approved radionuclide therapy for patients with gastroenteropancreatic neuroendocrine tumours (NETs) expressing somatostatin receptors. The 177Lu-octreotate therapy has shown promising results in clinical trials by prolonging progression-free survival, but complete responses are still uncommon. The aim of this study was to improve the 177Lu-octreotate therapy by means of combination therapy. To identify radiosensitising inhibitors, two cell lines, GOT1 and P-STS, derived from small intestinal neuroendocrine tumours (SINETs), were screened with 1,224 inhibitors alone or in combination with external radiation. The screening revealed that inhibitors of Hsp90 can potentiate the tumour cell-killing effect of radiation in a synergistic fashion (GOT1; false discovery rate <3.2×10-11). The potential for Hsp90 inhibitor ganetespib to enhance the anti-tumour effect of 177Lu-octreotate in an in vivo setting was studied in the somatostatin receptor-expressing GOT1 xenograft model. The combination led to a larger decrease in tumour volume relative to monotherapies and the tumour-reducing effect was shown to be synergistic. Using patient-derived tumour cells from eight metastatic SINETs, we could show that ganetespib enhanced the effect of 177Lu-octreotate therapy for all investigated patient tumours. Levels of Hsp90 protein expression were evaluated in 767 SINETs from 379 patients. We found that Hsp90 expression was upregulated in tumour cells relative to tumour stroma in the vast majority of SINETs. We conclude that Hsp90 inhibitors enhance the tumour-killing effect of 177Lu-octreotate therapy synergistically in SINET tumour models and suggest that this potentially promising combination should be further evaluated.

Immunotherapy Mythbusters in Head and Neck Cancer: The Abscopal Effect and Pseudoprogression

Atypical patterns of response to immunotherapy have been observed, including the abscopal effect and pseudoprogression. Although both are infrequent in head and neck squamous cell carcinoma, the synergism between radiation and checkpoint blockade therapy has generated excitement for exploitation of the abscopal effect. However, robust abscopal tumor regression observed in preclinical models has not translated to clinical experience. The optimal sequencing of radiotherapy with immunotherapy and dosage of radiation to target lesions to elicit this effect is being explored in clinical trials. Predictive markers of efficacy must be studied further to identify patients who may benefit from an abscopal effect and continued checkpoint inhibitor blockade beyond initial signs of radiologic progression. Given the rarity of pseudoprogression in head and neck squamous cell carcinoma, patients should be carefully selected to continue on immunotherapy, despite early radiologic signs of progression, given the risk of aggressive true progression and clinical deterioration that may result in missed opportunities for alternate treatments.

A comprehensive model for heat-induced radio-sensitisation

Combined radiotherapy (RT) and hyperthermia (HT) treatments may improve treatment outcome by heat induced radio-sensitisation. We propose an empirical cell survival model (AlphaR model) to describe this multimodality therapy. The model is motivated by the observation that heat induced radio-sensitisation may be explained by a reduction in the DNA damage repair capacity of heated cells. We assume that this repair is only possible up to a threshold level above which survival will decrease exponentially with dose. Experimental cell survival data from two cell lines (HCT116, Cal27) were considered along with that taken from the literature (baby hamster kidney [BHK] and Chinese hamster ovary cells [CHO]) for HT and combined RT-HT. The AlphaR model was used to study the dependence of clonogenic survival on treatment temperature, and thermal dose R2 ≥ 0.95 for all fits). For HT survival curves (0-80 CEM43 at 43.5-57 °C), the number of free fit AlphaR model parameters could be reduced to two. Both parameters increased exponentially with temperature. We derived the relative biological effectiveness (RBE) or HT treatments at different temperatures, to provide an alternative description of thermal dose, based on our AlphaR model. For combined RT-HT, our analysis is restricted to the linear quadratic arm of the model. We show that, for the range used (20-80 CEM43, 0-12 Gy), thermal dose is a valid indicator of heat induced radio-sensitisation, and that the model parameters can be described as a function thereof. Overall, the proposed model provides a flexible framework for describing cell survival curves, and may contribute to better quantification of heat induced radio-sensitisation, and thermal dose in general.

Abscopal, immunological effects of radiotherapy: Narrowing the gap between clinical and preclinical experiences

Radiotherapy-despite being a local therapy that meanwhile is characterized by an impressively high degree of spatial accuracy-can stimulate systemic phenomena which occasionally lead to regression and rejection of non-irradiated, distant tumor lesions. These abscopal effects of local irradiation have been observed in sporadic clinical case reports since the beginning of the 20th century, and extensive preclinical work has contributed to identify systemic anti-tumor immune responses as the underlying driving forces. Although abscopal tumor regression still remains a rare event in the radiotherapeutic routine, increasing numbers of cases are being reported, particularly since the clinical implementation of immune checkpoint inhibiting agents. Accordingly, interests to systematically exploit the therapeutic potential of radiotherapy-stimulated systemic responses are constantly growing. The present review briefly delineates the history of radiotherapy-induced abscopal effects and the activation of systemic anti-tumor immune responses by local irradiation. We discuss preclinical and clinical reports with specific focus on the corresponding controversies, and we propose issues that should be addressed in the future in order to narrow the gap between preclinical knowledge and clinical experiences.

Recommendations for In Vitro and In Vivo Testing of Magnetic Nanoparticle Hyperthermia Combined with Radiation Therapy

Magnetic nanoparticle (MNP)-mediated hyperthermia (MH) coupled with radiation therapy (RT) is a novel approach that has the potential to overcome various practical difficulties encountered in cancer treatment. In this work, we present recommendations for the in vitro and in vivo testing and application of the two treatment techniques. These recommendations were developed by the members of Working Group 3 of COST Action TD 1402: Multifunctional Nanoparticles for Magnetic Hyperthermia and Indirect Radiation Therapy ("Radiomag"). The purpose of the recommendations is not to provide definitive answers and directions but, rather, to outline those tests and considerations that a researcher must address in order to perform in vitro and in vivo studies. The recommendations are divided into 5 parts: (a) in vitro evaluation of MNPs; (b) in vitro evaluation of MNP-cell interactions; (c) in vivo evaluation of the MNPs; (d) MH combined with RT; and (e) pharmacokinetic studies of MNPs. Synthesis and characterization of the MNPs, as well as RT protocols, are beyond the scope of this work.

A comparison of cell survival and heat shock protein expression after radiation in normal dermal fibroblasts, microvascular endothelial cells, and different head and neck squamous carcinoma cell lines

OBJECTIVES

Head and neck squamous cell carcinoma (HNSCC) shows increased radioresistance due to the manipulation of homeostatic mechanisms like the heat shock response. This study intended to comparatively analyze effects of ionizing radiation on different HNSCC cell lines (PCI) and normal human dermal fibroblasts (NHFs) and human dermal microvascular endothelial cells (HDMECs) to uncover differences in radiation coping strategies.

MATERIALS AND METHODS

Proliferation (BrdU assay), apoptosis (caspase 3/7) and intracellular protein expression of heat shock protein (HSP)-70, and phosphorylated and total HSP27, determined by enzyme-linked immunosorbent assay (ELISA), were analyzed after exposure to increasing doses of ionizing radiation (2, 6, and 12 Gray, Gy).

RESULTS

Cell count decreased dose-dependently, but PCI cell lines consistently showed higher numbers compared to NHF and HDMEC. Likewise, high doses reduced cell proliferation, but low-dose radiation (2 Gy) instead increased proliferation in PCI 9 and 52. Apoptosis was not detectable in PCI cell lines. Basic HSP70 expression was high in PCI cells with little additional increase by irradiation. PCI cells yielded high basic total HSP27 concentrations but irradiation dose-dependently increased HSP27 in HDMEC, NHF, and PCI cells. Phosphorylated HSP27 concentrations were highest in NHF.

CONCLUSION

PCI cell lines showed higher resistance to dose-dependent reduction in cell number, proliferation, and protection from apoptosis compared to NHF and HDMEC. In parallel, we observed a high basic and radiation-induced expression of intracellular HSP70 leading to the assumption that the radioresistance of PCI cells is conferred by HSP70.

CLINICAL RELEVANCE

HNSCC use HSP to escape radiation-induced apoptosis and certain subtypes might increase proliferation after low-dose irradiation.

Combining radiation with hyperthermia: a multiscale model informed by in vitro experiments

Combined radiotherapy and hyperthermia offer great potential for the successful treatment of radio-resistant tumours through thermo-radiosensitization. Tumour response heterogeneity, due to intrinsic, or micro-environmentally induced factors, may greatly influence treatment outcome, but is difficult to account for using traditional treatment planning approaches. Systems oncology simulation, using mathematical models designed to predict tumour growth and treatment response, provides a powerful tool for analysis and optimization of combined treatments. We present a framework that simulates such combination treatments on a cellular level. This multiscale hybrid cellular automaton simulates large cell populations (up to 107 cells) in vitro, while allowing individual cell-cycle progression, and treatment response by modelling radiation-induced mitotic cell death, and immediate cell kill in response to heating. Based on a calibration using a number of experimental growth, cell cycle and survival datasets for HCT116 cells, model predictions agreed well (R2 > 0.95) with experimental data within the range of (thermal and radiation) doses tested (0-40 CEM43, 0-5 Gy). The proposed framework offers flexibility for modelling multimodality treatment combinations in different scenarios. It may therefore provide an important step towards the modelling of personalized therapies using a virtual patient tumour.

A novel HSP90 inhibitor with reduced hepatotoxicity synergizes with radiotherapy to induce apoptosis, abrogate clonogenic survival, and improve tumor control in models of colorectal cancer

The chaperone heat shock protein 90 (HSP90) crucially supports the maturation, folding, and stability of a variety of client proteins which are of pivotal importance for the survival and proliferation of cancer cells. Consequently, targeting of HSP90 has emerged as an attractive strategy of anti-cancer therapy, and it appears to be particularly effective in the context of molecular sensitization towards radiotherapy as has been proven in preclinical models of different cancer entities. However, so far the clinical translation has largely been hampered by suboptimal pharmacological properties and serious hepatotoxicity of first- and second-generation HSP90 inhibitors. Here, we report on NW457, a novel radicicol-derived member of the pochoxime family with reduced hepatotoxicity, how it inhibits the DNA damage response and how it synergizes with ionizing irradiation to induce apoptosis, abrogate clonogenic survival, and improve tumor control in models of colorectal cancer in vitro and in vivo.

Hsp90α regulates ATM and NBN functions in sensing and repair of DNA double-strand breaks

The molecular chaperone heat shock protein 90 (Hsp90α) regulates cell proteostasis and mitigates the harmful effects of endogenous and exogenous stressors on the proteome. Indeed, the inhibition of Hsp90α ATPase activity affects the cellular response to ionizing radiation (IR). Although the interplay between Hsp90α and several DNA damage response (DDR) proteins has been reported, its role in the DDR is still unclear. Here, we show that ataxia-telangiectasia-mutated kinase (ATM) and nibrin (NBN), but not 53BP1, RAD50, and MRE11, are Hsp90α clients as the Hsp90α inhibitor 17-(allylamino)-17-demethoxygeldanamycin (17-AAG) induces ATM and NBN polyubiquitination and proteosomal degradation in normal fibroblasts and lymphoblastoid cell lines. Hsp90α-ATM and Hsp90α-NBN complexes are present in unstressed and irradiated cells, allowing the maintenance of ATM and NBN stability that is required for the MRE11/RAD50/NBN complex-dependent ATM activation and the ATM-dependent phosphorylation of both NBN and Hsp90α in response to IR-induced DNA double-strand breaks (DSBs). Hsp90α forms a complex also with ph-Ser1981-ATM following IR. Upon phosphorylation, NBN dissociates from Hsp90α and translocates at the DSBs, while phThr5/7-Hsp90α is not recruited at the damaged sites. The inhibition of Hsp90α affects nuclear localization of MRE11 and RAD50, impairs DDR signaling (e.g., BRCA1 and CHK2 phosphorylation), and slows down DSBs repair. Hsp90α inhibition does not affect DNA-dependent protein kinase (DNA-PK) activity, which possibly phosphorylates Hsp90α and H2AX after IR. Notably, Hsp90α inhibition causes H2AX phosphorylation in proliferating cells, this possibly indicating replication stress events. Overall, present data shed light on the regulatory role of Hsp90α on the DDR, controlling ATM and NBN stability and influencing the DSBs signaling and repair.

Current applications and future prospects of nanomaterials in tumor therapy

Tumors are one of the most serious human diseases and cause numerous global deaths per year. In spite of many strategies applied in tumor therapy, such as radiation therapy, chemotherapy, surgery, and a combination of these treatments, tumors are still the foremost killer worldwide among human diseases, due to their specific limitations, such as multidrug resistance and side effects. Therefore, it is urgent and necessary to develop new strategies for tumor therapy. Recently, the fast development of nanoscience has paved the way for designing new strategies to treat tumors. Nanomaterials have shown great potential in tumor therapy, due to their unique properties, including passive targeting, hyperthermia effects, and tumor-specific inhibition. This review summarizes the recent progress using the innate antitumor properties of metallic and nonmetallic nanomaterials to treat tumors, and related challenges and prospects are discussed.

Self-harm to preferentially harm the pathogens within: non-specific stressors in innate immunity

Therapies with increasing specificity against pathogens follow the immune system's evolutionary course in maximizing host defence while minimizing self-harm. Nevertheless, even completely non-specific stressors, such as reactive molecular species, heat, nutrient and oxygen deprivation, and acidity can be used to preferentially harm pathogens. Strategic use of non-specific stressors requires exploiting differences in stress vulnerability between pathogens and hosts. Two basic vulnerabilities of pathogens are: (i) the inherent vulnerability to stress of growth and replication (more immediately crucial for pathogens than for host cells) and (ii) the degree of pathogen localization, permitting the host's use of locally and regionally intense stress. Each of the various types of non-specific stressors is present during severe infections at all levels of localization: (i) ultra-locally within phagolysosomes, (ii) locally at the infected site, (iii) regionally around the infected site and (iv) systemically as part of the acute-phase response. We propose that hosts strategically use a coordinated system of non-specific stressors at local, regional and systemic levels to preferentially harm the pathogens within. With the rising concern over emergence of resistance to specific therapies, we suggest more scrutiny of strategies using less specific therapies in pathogen control. Hosts' active use of multiple non-specific stressors is likely an evolutionarily basic defence whose retention underlies and supplements the well-recognized immune defences that directly target pathogens.

Laser Ablation of Recurrent Malignant Gliomas

Recurrent malignant glioma continues to be a clinical challenge, and repeat surgery is an option in only select patients. Stereotactic laser ablation, a new minimally invasive technique, can be used as an alternative to surgery. We review the current literature on laser ablation for recurrent malignant gliomas as well as discuss practical and theoretical advantages and disadvantages of this emerging technique in comparison with repeat surgery or radiation. We also discuss the potential for laser ablation to augment adjuvant therapies, namely, chemotherapy, radiation, and immunotherapy.

Melatonin enhances hyperthermia-induced apoptotic cell death in human leukemia cells

Melatonin is an endogenous indoleamine with a wide range of biological functions. In addition to modulating circadian rhythms, it plays important roles in the health as an antioxidant. Melatonin has also the ability to induce apoptosis in cancer cells and to enhance the antitumoral activity of chemotherapeutic agents. In this study, the effect of melatonin on hyperthermia-induced apoptosis was explored using human leukemia cells. The results demonstrate that melatonin greatly improved the cytotoxicity of hyperthermia in U937 cells. The potentiation of cell death was achieved with 1 mmol/L concentrations of the indoleamine but not with concentrations close to physiological levels in blood (1 nmol/L). This effect was associated to an enhancement of the apoptotic response, revealed by an increase in cells with hypodiploid DNA content and activation of multiple caspases (caspase-2, caspase-3, caspase-8, and caspase-9). Melatonin also increased hyperthermia-induced Bid activation as well as translocation of Bax from the cytosol to mitochondria and cytochrome c release. Hyperthermia-provoked apoptosis and potentiation by melatonin were abrogated by a broad-spectrum caspase inhibitor (z-VAD-fmk) as well as by specific inhibitors against caspase-8 or caspase-3. In contrast, blocking of the mitochondrial pathway of apoptosis either with a caspase-9 inhibitor or overexpressing the anti-apoptotic protein Bcl-2 (U937/Bcl-2) reduced the number of apoptotic cells in response to hyperthermia but it was unable to suppress melatonin enhancement. Melatonin appears to modulate the apoptotic response triggered by hyperthermia in a cell type-specific manner as similar results were observed in HL-60 but not in K562 or MOLT-3 cells.

Quantitative Study of Elasticity of Rabbit VX2 Liver Tumor with Alternated Cooling and Heating Treatment based on ARFI Ultrasound Imaging Technique

Acoustic radiation force impulse (ARFI) ultrasound imaging technique is used to quantitatively evaluate the elasticity of rabbit VX₂ liver tumor with alternated cooling and heating treatment (ACHT). ACHT was performed on fifteen VX₂ liver tumor models established in fifteen male New Zealand white rabbits with open tumor plant. ARFI was performed on day 0, 1, 7 and 14 after ACHT and shear wave velocity (SWV) in ARFI was recorded to evaluate the elasticity of the treated area. The SWV value of the lesion on day 0, 1, 7 and 14 was 2.33 ± 0.19 m/s, 3.09 ± 0.40 m/s, 2.64 ± 0.37 m/s and 2.26 ± 0.24 m/s, respectively, indicating the treated areas get stiffer on day 1 and then get softer gradually by day. All the difference between adjacent time points was statistically significant. The SWV value of different parts on day 7 approved that the hardness of the treated area is heterogenous: the treated area in the center >the peripheral strip-shaped area >normal liver tissues, consistent with pathological changes. Meanwhile, ARFI combined with conventional US imaging can qualitatively and quantitatively exam the healing process of rabbit VX₂ liver tumor after ACHT, and corresponds well to the pathological results.

Improving efficacy of hyperthermia in oncology by exploiting biological mechanisms

It has long been established that hyperthermia increases the therapeutic benefit of radiation and chemotherapy in cancer treatment. During the last few years there have been substantial technical improvements in the sources used to apply and measure heat, which greatly increases enthusiasm for the clinical use of hyperthermia. These advances are converging with a better understanding of the physiological and molecular effects of hyperthermia. Therefore, we are now at a juncture where the parameters that will influence the efficacy of hyperthermia in cancer treatment can be optimised in a more systematic and rational manner. In addition, the novel insights in hyperthermia's many biological effects on tumour cells will ultimately result in new treatment regimes. For example, the molecular effects of hyperthermia on the essential cellular process of DNA repair suggest novel combination therapies, with DNA damage response targeting drugs that should now be clinically explored. Here, we provide an overview of recent studies on the various macroscopic and microscopic biological effects of hyperthermia. We indicate the significance of these effects on current treatments and suggest how they will help design novel future treatments.

Hyperthermia adds to trabectedin effectiveness and thermal enhancement is associated with BRCA2 degradation and impairment of DNA homologous recombination repair

The tetrahydroisoquinoline trabectedin is a marine compound with approved activity against human soft-tissue sarcoma. It exerts antiproliferative activity mainly by specific binding to the DNA and inducing DNA double-strand breaks (DSB). As homologous recombination repair (HRR)-deficient tumors are more susceptible to trabectedin, hyperthermia-mediated on-demand induction of HRR deficiency represents a novel and promising strategy to boost trabectedin treatment. For the first time, we demonstrate enhancement of trabectedin effectiveness in human sarcoma cell lines by heat and characterize cellular events and molecular mechanisms related to heat-induced effects. Hyperthermic temperatures (41.8 or 43°C) enhanced significantly trabectedin-related clonogenic cell death and G2/M cell cycle arrest followed by cell type-dependent induction of apoptosis or senescence. Heat combination increased accumulation of γH2AX foci as key marker of DSBs. Expression of BRCA2 protein, an integral protein of the HRR machinery, was significantly decreased by heat. Consequently, recruitment of downstream RAD51 to γH2AX-positive repair foci was almost abolished indicating relevant impairment of HRR by heat. Accordingly, enhancement of trabectedin effectiveness was significantly augmented in BRCA2-proficient cells by hyperthermia and alleviated in BRCA2 knockout or siRNA-transfected BRCA2 knockdown cells. In peripheral blood mononuclear cells isolated from sarcoma patients, increased numbers of nuclear γH2AX foci were detected after systemic treatment with trabectedin and hyperthermia of the tumor region. The findings establish BRCA2 degradation by heat as a key factor for a novel treatment strategy that allows targeted chemosensitization to trabectedin and other DNA damaging antitumor drugs by on-demand induction of HRR deficiency.

Adenosine can thwart antitumor immune responses elicited by radiotherapy : Therapeutic strategies alleviating protumor ADO activities

BACKGROUND

By studying the bioenergetic status we could show that the development of tumor hypoxia is accompanied, apart from myriad other biologically relevant effects, by a substantial accumulation of adenosine (ADO). ADO has been shown to act as a strong immunosuppressive agent in tumors by modulating the innate and adaptive immune system. In contrast to ADO, standard radiotherapy (RT) can either stimulate or abrogate antitumor immune responses. Herein, we present ADO-mediated mechanisms that may thwart antitumor immune responses elicited by RT.

MATERIALS AND METHODS

An overview of the generation, accumulation, and ADO-related multifaceted inhibition of immune functions, contrasted with the antitumor immune effects of RT, is provided.

RESULTS

Upon hypoxic stress, cancer cells release ATP into the extracellular space where nucleotides are converted into ADO by hypoxia-sensitive, membrane-bound ectoenzymes (CD39/CD73). ADO actions are mediated upon binding to surface receptors, mainly A2A receptors on tumor and immune cells. Receptor activation leads to a broad spectrum of strong immunosuppressive properties facilitating tumor escape from immune control. Mechanisms include (1) impaired activity of CD4 (+) T and CD8 (+) T, NK cells and dendritic cells (DC), decreased production of immuno-stimulatory lymphokines, and (2) activation of Treg cells, expansion of MDSCs, promotion of M2 macrophages, and increased activity of major immunosuppressive cytokines. In addition, ADO can directly stimulate tumor proliferation and angiogenesis.

CONCLUSION

ADO mechanisms described can thwart antitumor immune responses elicited by RT. Therapeutic strategies alleviating tumor-promoting activities of ADO include respiratory hyperoxia or mild hyperthermia, inhibition of CD39/CD73 ectoenzymes or blockade of A2A receptors, and inhibition of ATP-release channels or ADO transporters.

Thermoradiotherapy planning: Integration in routine clinical practice

Planning of combined radiotherapy and hyperthermia treatments should be performed taking the synergistic action between the two modalities into account. This work evaluates the available experimental data on cytotoxicity of combined radiotherapy and hyperthermia treatment and the requirements for integration of hyperthermia and radiotherapy treatment planning into a single planning platform. The underlying synergistic mechanisms of hyperthermia include inhibiting DNA repair, selective killing of radioresistant hypoxic tumour tissue and increased radiosensitivity by enhanced tissue perfusion. Each of these mechanisms displays different dose-effect relations, different optimal time intervals and different optimal sequences between radiotherapy and hyperthermia. Radiosensitisation can be modelled using the linear-quadratic (LQ) model to account for DNA repair inhibition by hyperthermia. In a recent study, an LQ model-based thermoradiotherapy planning (TRTP) system was used to demonstrate that dose escalation by hyperthermia is equivalent to ∼10 Gy for prostate cancer patients treated with radiotherapy. The first step for more reliable TRTP is further expansion of the data set of LQ parameters for normally oxygenated normal and tumour tissue valid over the temperature range used clinically and for the relevant time intervals between radiotherapy and hyperthermia. The next step is to model the effect of hyperthermia in hypoxic tumour cells including the physiological response to hyperthermia and the resulting reoxygenation. Thermoradiotherapy planning is feasible and a necessity for an optimal clinical application of hyperthermia combined with radiotherapy in individual patients.

Radio-Immunotherapy-Induced Immunogenic Cancer Cells as Basis for Induction of Systemic Anti-Tumor Immune Responses - Pre-Clinical Evidence and Ongoing Clinical Applications

Radiotherapy (RT) primarily aims to locally destroy the tumor via the induction of DNA damage in the tumor cells. However, the so-called abscopal, namely systemic and immune–mediated, effects of RT move over more and more in the focus of scientists and clinicians since combinations of local irradiation with immune therapy have been demonstrated to induce anti-tumor immunity. We here summarize changes of the phenotype and microenvironment of tumor cells after exposure to irradiation, chemotherapeutic agents, and immune modulating agents rendering the tumor more immunogenic. The impact of therapy-modified tumor cells and damage-associated molecular patterns on local and systemic control of the primary tumor, recurrent tumors, and metastases will be outlined. Finally, clinical studies affirming the bench-side findings of interactions and synergies of radiation therapy and immunotherapy will be discussed. Focus is set on combination of radio(chemo)therapy (RCT) with immune checkpoint inhibitors, growth factor inhibitors, and chimeric antigen receptor T-cell therapy. Well-deliberated combination of RCT with selected immune therapies and growth factor inhibitors bear the great potential to further improve anti-cancer therapies.

HSP90 inhibition as a means of radiosensitizing resistant, aggressive soft tissue sarcomas

Radiotherapy is an essential part of multi-modal treatment for soft tissue sarcomas. Treatment failure is commonly attributed to radioresistance, but comprehensive analyses of radiosensitivity are not available, and suitable biomarkers or candidates for targeted radiosensitization are scarce. Here, we systematically analyzed the intrinsic radioresistance of a panel of soft tissue sarcoma cell lines, and extracted scores of radioresistance by principal component analysis (PCA). To identify molecular markers of radioresistance, transcriptomic profiling of DNA damage response regulators was performed. The expression levels of HSP90 and its clients ATR, ATM, and NBS1 revealed strong, positive correlations with the PCA-derived radioresistance scores. Their functional involvement was addressed by HSP90 inhibition, which preferentially sensitized radioresistant sarcoma cells and was accompanied by delayed γ-H2AX foci clearance and HSP90 client protein degradation. The induction of apoptosis and necrosis was not significantly enhanced, but increased levels of basal and irradiation-induced senescence upon HSP90 inhibition were detected. Finally, evaluation of our findings in the TCGA soft tissue sarcoma cohort revealed elevated expression levels of HSP90, ATR, ATM, and NBS1 in a relevant subset of cases with particularly poor prognosis, which might preferentially benefit from HSP90 inhibition in combination with radiotherapy in the future.