Role of Acid Sphingomyelinase and Ceramide in Mechano-Acoustic Enhancement of Tumor Radiation Responses

Radiation enhancement using focussed ultrasound-stimulated microbubbles for head and neck cancer: A phase 1 clinical trial

BACKGROUND AND PURPOSE

Preclinical research demonstrated that the exposure of microbubbles (intravascular gas microspheres) to focussed ultrasound within the targeted tumour upregulates pro-apoptotic pathways and enhances radiation-induced tumour cell death. This study aimed to assess the safety and efficacy of magnetic resonance (MR)-guided focussed ultrasound-stimulated microbubbles (MRgFUS-MB) for head and neck cancers (HN).

MATERIALS AND METHODS

This prospective phase 1 clinical trial included patients with newly diagnosed or recurrent HN cancer (except nasopharynx malignancies) for whom locoregional radiotherapy with radical- or palliative-intent as deemed appropriate. Patients with contraindications for microbubble administration or contrast-enhanced MR were excluded. MR-coupled focussed ultrasound sonicated intravenously administered microbubbles within the MR-guided target volume. Patients receiving 5-10 and 33-35 radiation fractions were planned for 2 and 3 MRgFUS-MB treatments, respectively. Primary endpoint was toxicity per CTCAEv5.0. Secondary endpoint was tumour response at 3 months per RECIST 1.1 criteria.

RESULTS

Twelve patients were enrolled between Jun/2020 and Nov/2023, but 1 withdrew consent. Eleven patients were included in safety analysis. Median follow-up was 7 months (range, 0.3-38). Most patients had oropharyngeal cancer (55 %) and received 20-30 Gy/5-10 fractions (63 %). No systemic toxicity or MRgFUS-MB-related adverse events occurred. The most severe acute adverse events were radiation-related grade 3 toxicities in 6 patients (55 %; dermatitis in 3, mucositis in 1, dysphagia in 6). No radiation necrosis or grade 4/5 toxicities were reported. 8 patients were included in the 3-month tumour response assessment: 4 had partial response (50 %), 3 had complete response (37.5 %), and 1 had progressive disease (12.5 %).

CONCLUSIONS

MRgFUS-MB treatment was safe and associated with high rates of tumour response at 3 months.

Radiation enhancement using focussed ultrasound-stimulated microbubbles for breast cancer: A Phase 1 clinical trial

BACKGROUND

Preclinical studies have demonstrated that tumour cell death can be enhanced 10- to 40-fold when radiotherapy is combined with focussed ultrasound-stimulated microbubble (FUS-MB) treatment. The acoustic exposure of microbubbles (intravascular gas microspheres) within the target volume causes bubble cavitation, which induces perturbation of tumour vasculature and activates endothelial cell apoptotic pathways responsible for the ablative effect of stereotactic body radiotherapy. Subsequent irradiation of a microbubble-sensitised tumour causes rapid increased tumour death. The study here presents the mature safety and efficacy outcomes of magnetic resonance (MR)-guided FUS-MB (MRgFUS-MB) treatment, a radioenhancement therapy for breast cancer.

METHODS AND FINDINGS

This prospective, single-center, single-arm Phase 1 clinical trial included patients with stages I-IV breast cancer with in situ tumours for whom breast or chest wall radiotherapy was deemed adequate by a multidisciplinary team (clinicaltrials.gov identifier: NCT04431674). Patients were excluded if they had contraindications for contrast-enhanced MR or microbubble administration. Patients underwent 2 to 3 MRgFUS-MB treatments throughout radiotherapy. An MR-coupled focussed ultrasound device operating at 800 kHz and 570 kPa peak negative pressure was used to sonicate intravenously administrated microbubbles within the MR-guided target volume. The primary outcome was acute toxicity per Common Terminology Criteria for Adverse Events (CTCAE) v5.0. Secondary outcomes were tumour response at 3 months and local control (LC). A total of 21 female patients presenting with 23 primary breast tumours were enrolled and allocated to intervention between August/2020 and November/2022. Three patients subsequently withdrew consent and, therefore, 18 patients with 20 tumours were included in the safety and LC analyses. Two patients died due to progressive metastatic disease before 3 months following treatment completion and were excluded from the tumour response analysis. The prescribed radiation doses were 20 Gy/5 fractions (40%, n = 8/20), 30 to 35 Gy/5 fractions (35%, n = 7/20), 30 to 40 Gy/10 fractions (15%, n = 3/20), and 66 Gy/33 fractions (10%, n = 2/20). The median follow-up was 9 months (range, 0.3 to 29). Radiation dermatitis was the most common acute toxicity (Grade 1 in 16/20, Grade 2 in 1/20, and Grade 3 in 2/20). One patient developed grade 1 allergic reaction possibly related to microbubbles administration. At 3 months, 18 tumours were evaluated for response: 9 exhibited complete response (50%, n = 9/18), 6 partial response (33%, n = 6/18), 2 stable disease (11%, n = 2/18), and 1 progressive disease (6%, n = 1/18). Further follow-up of responses indicated that the 6-, 12-, and 24-month LC rates were 94% (95% confidence interval [CI] [84%, 100%]), 88% (95% CI [75%, 100%]), and 76% (95% CI [54%, 100%]), respectively. The study's limitations include variable tumour sizes and dose fractionation regimens and the anticipated small sample size typical for a Phase 1 clinical trial.

CONCLUSIONS

MRgFUS-MB is an innovative radioenhancement therapy associated with a safe profile, potentially promising responses, and durable LC. These results warrant validation in Phase 2 clinical trials.

TRIAL REGISTRATION

clinicaltrials.gov, identifier NCT04431674.

Sphingolipid-Induced Bone Regulation and Its Emerging Role in Dysfunction Due to Disease and Infection

The human skeleton is a metabolically active system that is constantly regenerating via the tightly regulated and highly coordinated processes of bone resorption and formation. Emerging evidence reveals fascinating new insights into the role of sphingolipids, including sphingomyelin, sphingosine, ceramide, and sphingosine-1-phosphate, in bone homeostasis. Sphingolipids are a major class of highly bioactive lipids able to activate distinct protein targets including, lipases, phosphatases, and kinases, thereby conferring distinct cellular functions beyond energy metabolism. Lipids are known to contribute to the progression of chronic inflammation, and notably, an increase in bone marrow adiposity parallel to elevated bone loss is observed in most pathological bone conditions, including aging, rheumatoid arthritis, osteoarthritis, and osteomyelitis. Of the numerous classes of lipids that form, sphingolipids are considered among the most deleterious. This review highlights the important primary role of sphingolipids in bone homeostasis and how dysregulation of these bioactive metabolites appears central to many chronic bone-related diseases. Further, their contribution to the invasion, virulence, and colonization of both viral and bacterial host cell infections is also discussed. Many unmet clinical needs remain, and data to date suggest the future use of sphingolipid-targeted therapy to regulate bone dysfunction due to a variety of diseases or infection are highly promising. However, deciphering the biochemical and molecular mechanisms of this diverse and extremely complex sphingolipidome, both in terms of bone health and disease, is considered the next frontier in the field.

A study combining microbubble-mediated focused ultrasound and radiation therapy in the healthy rat brain and a F98 glioma model

Focused Ultrasound (FUS) has been shown to sensitize tumors outside the brain to Radiotherapy (RT) through increased ceramide-mediated apoptosis. This study investigated the effects of FUS + RT in healthy rodent brains and F98 gliomas. Tumors, or striata in healthy rats, were targeted with microbubble-mediated, pulsed FUS (220 kHz, 102-444 kPa), followed by RT (4, 8, 15 Gy). FUS + RT (8, 15 Gy) resulted in ablative lesions, not observed with FUS or RT only, in healthy tissue. Lesions were visible using Magnetic Resonance Imaging (MRI) within 72 h and persisted until 21 days post-treatment, indicating potential applications in ablative neurosurgery. In F98 tumors, at 8 and 15 Gy, where RT only had significant effects, FUS + RT offered limited improvements. At 4 Gy, where RT had limited effects compared with untreated controls, FUS + RT reduced tumor volumes observed on MRI by 45-57%. However, survival benefits were minimal (controls: 27 days, RT: 27 days, FUS + RT: 28 days). Histological analyses of tumors 72 h after FUS + RT (4 Gy) showed 93% and 396% increases in apoptosis, and 320% and 336% increases in vessel-associated ceramide, compared to FUS and RT only. Preliminary evidence shows that FUS + RT may improve treatment of glioma, but additional studies are required to optimize effect size.

Novel MRI-guided focussed ultrasound stimulated microbubble radiation enhancement treatment for breast cancer

Preclinical studies have demonstrated focused ultrasound (FUS) stimulated microbubble (MB) rupture leads to the activation of acid sphingomyelinase-ceramide pathway in the endothelial cells. When radiotherapy (RT) is delivered concurrently with FUS-MB, apoptotic pathway leads to increased cell death resulting in potent radiosensitization. Here we report the first human trial of using magnetic resonance imaging (MRI) guided FUS-MB treatment in the treatment of breast malignancies. In the phase 1 prospective interventional study, patients with breast cancer were treated with fractionated RT (5 or 10 fractions) to the disease involving breast or chest wall. FUS-MB treatment was delivered before 1st and 5th fractions of RT (within 1 h). Eight patients with 9 tumours were treated. All 7 evaluable patients with at least 3 months follow-up treated for 8 tumours had a complete response in the treated site. The maximum acute toxicity observed was grade 2 dermatitis in 1 site, and grade 1 in 8 treated sites, at one month post RT, which recovered at 3 months. No RT-related late effect or FUS-MB related toxicity was noted. This study demonstrated safety of combined FUS-MB and RT treatment. Promising response rates suggest potential strong radiosensitization effects of the investigational modality.Trial registration: clinicaltrials.gov, identifier NCT04431674.

Radiation combined with ultrasound and microbubbles: A potential novel strategy for cancer treatment

Cancer is one of the leading causes of death worldwide. Several emerging technologies are helping to battle cancer. Cancer therapies have been effective at killing cancer cells, but a large portion of patients still die to this disease every year. As such, more aggressive treatments of primary cancers are employed and have been shown to be capable of saving a greater number of lives. Recent research advances the field of cancer therapy by employing the use of physical methods to alter tumor biology. It uses microbubbles to enhance radiation effect by damaging tumor vasculature followed by tumor cell death. The technique can specifically target tumor volumes by conforming ultrasound fields capable of microbubbles stimulation and localizing it to avoid vascular damage in surrounding tissues. Thus, this new application of ultrasound-stimulated microbubbles (USMB) can be utilized as a novel approach to cancer therapy by inducing vascular disruption resulting in tumor cell death. Using USMB alongside radiation has showed to augment the anti-vascular effect of radiation, resulting in enhanced tumor response. Recent work with nanobubbles has shown vascular permeation into intracellular space, extending the use of this new treatment method to potentially further improve the therapeutic effect of the ultrasound-based therapy. The significant enhancement of localized tumor cell kill means that radiation-based treatments can be made more potent with lower doses of radiation. This technique can manifest a greater impact on radiation oncology practice by increasing treatment effectiveness significantly while reducing normal tissue toxicity. This review article summarizes the past and recent advances in USMB enhancement of radiation treatments. The review mainly focuses on preclinical findings but also highlights some clinical findings that use USMB as a therapeutic modality in cancer therapy.

Ultrasound-stimulated microbubbles enhancement of fractionated radiation for tumor treatment

BACKGROUND

Radiation therapy (XRT) causes numerous biological changes in tumor microenvironment. Radiation vascular response, due to endothelial disruption, can influence treatment outcomes in a dose-dependent manner. Ultrasound-stimulated microbubbles (USMB) have also been demonstrated to create a vascular response in the tumor microenvironment and enhance tumor response when used in combination with XRT. Single doses of 8-10 Gy are known to induce activation of acid sphingomyelinase (ASMase)-induced ceramide production, causing vascular damage. Destruction of vasculature results in endothelial apoptosis followed by tumor cell death. The effect of tumor response is known to be synergistic by 10-fold higher cell kill observed when USMB is combined with radiation.

METHODS

In this study, we used an USMB approach in combination with conventional low dose fractionated radiation to enhance endothelial cell responses to XRT in human PC3 prostate cancer xenograft model. Mice were divided into untreated, USMB therapy, fractionated XRT, and combined USMB therapy followed by XRT (USMB + XRT) groups. USMB therapy was delivered twice per week in the USMB-alone and combined USMB + XRT treatment groups over four weeks. Radiation treatments were delivered in fractions of 2 Gy/day (total 40 Gy in 20 fractions, BED₁₀ = 48 Gy) in the XRT-alone and combined USMB + XRT groups. The treatment outcome was evaluated using histopathology, power Doppler, and immunohistochemistry assays.

RESULTS

Tumor growth assessment showed that sizes of tumors increased in the control and the single treatment groups over a treatment period of four weeks, but significantly decreased with the combined treatments of USMB + XRT. Immunohistochemical analysis indicated a statistically significant vascular disruption in mice that received treatment involving a full 4-week schedule of combined (USMB + XRT) treatments. A statistically significant increase in vascular disruption was demonstrated through CD68 and trichrome fibrosis staining. Changes in local perfusion assessed using high-frequency power Doppler imaging demonstrated attenuated blood flow in the combined group.

DISCUSSION AND CONCLUSIONS

This work demonstrates the efficacy of using USMB as a radiation sensitizer in a mouse model of human PC3 tumor xenograft. This radiation treatment enhancement modality has the advantage of targeting tumor vasculature with ultrasound stimulation that can be implemented prior to radiation treatment.

Radioenhancement with the Combination of Docetaxel and Ultrasound Microbubbles: In Vivo Prostate Cancer

Using an in vitro prostate cancer model, we previously demonstrated the significant enhancement of radiotherapy (XRT) with the combined treatment of docetaxel (Taxotere; TXT) and ultrasound-microbubbles (USMB). Here, we extend these findings to an in vivo cancer model. Severe combined immune-deficient male mice were xenografted with the PC-3 prostate cancer cell line in the hind leg and treated with USMB, TXT, radiotherapy (XRT), and their combinations. The tumors were imaged with ultrasound pre-treatment and 24 h post-treatment, following which they were extracted for the histological analysis of the tumor-cell death (D_N; H&E) and apoptosis (D_A; TUNEL). The tumors' growths were assessed for up to ~6 weeks and analysed using the exponential Malthusian tumor-growth model. The tumors' doubling time (V_T) was characterized as growth (positive) or shrinkage (negative). The cellular death and apoptosis increased ~5-fold with the TXT + USMB + XRT (D_n = 83% and D_a = 71%) compared to the XRT alone (D_n = 16% and D_a = 14%), and by ~2-3-fold with the TXT + XRT (D_n = 50% and D_a = 38%) and USMB + XRT (D_n = 45% and D_a = 27%) compared to the XRT. The USMB enhanced the cellular bioeffects of the TXT by ~2-5-fold with the TXT + USMB (D_n = 42% and D_a = 50%), compared with the TXT alone (D_n = 19% and D_a = 9%). The USMB alone caused cell death (D_n = 17% and D_a = 10%) compared to the untreated control (D_n = 0.4% and D_a = 0%). The histological cellular bioeffects were correlated with the changes in the ultrasound RF mid-band-fit data, which were associated with the cellular morphology. The linear regression analysis displayed a positive linear correlation between the mid-band fit and the overall cell death (R² = 0.9164), as well as a positive linear correlation between the mid-band fit and the apoptosis (R² = 0.8530). These results demonstrate a correlation between the histological and spectral measurements of the tissue microstructure and that cellular morphological changes can be detected by ultrasound scattering analysis. In addition, the tumor volumes from the triple-combination treatment were significantly smaller than those from the control, XRT, USMB + XRT, and TXT + XRT, from day 2 onward. The TXT + USMB + XRT-treated tumors shrank from day 2 and at each subsequent time-point measured (V_T ~-6 days). The growth of the XRT-treated tumors was inhibited during the first 16 days, following which the tumors grew (V_T ~9 days). The TXT + XRT and USMB + XRT groups displayed an initial decrease in tumor size (day 1-14; TXT + XRT V_T ~-12 days; USMB + XRT V_T ~-33 days), followed by a growth phase (day 15-37; TXT + XRT V_T ~11 days; USMB + XRT V_T ~22 days). The triple-combination therapy induced tumor shrinkage to a greater extent than any of the other treatments. This study demonstrates the in vivo radioenhancement potential of chemotherapy combined with therapeutic ultrasound-microbubble treatment in inducing cell death and apoptosis, as well as long-term tumor shrinkage.

MR-guided ultrasound-stimulated microbubble therapy enhances radiation-induced tumor response

High intensity focused ultrasound (HIFU) systems have been approved for therapeutic ultrasound delivery to cause tissue ablation or induced hyperthermia. Microbubble agents have also been used in combination with sonication exposures. These require temperature feedback and monitoring to prevent unstable cavitation and prevent excess tissue heating. Previous work has utilized lower power and pressure to oscillate microbubbles and transfer energy to endothelial cells in the absence of thermally induced damage that can radiosensitize tumors. This work investigated whether reduced acoustic power and pressure on a commercial available MR-integrated HIFU system could result in enhanced radiation-induced tumor response after exposure to ultrasound-stimulated microbubbles (USMB) therapy. A commercially available MR-integrated HIFU system was used with a hyperthermia system calibration provided by the manufacturer. The ultrasound transducer was calibrated to reach a peak negative pressure of - 750 kPa. Thirty male New Zealand white rabbits bearing human derived PC3 tumors were grouped to receive no treatment, 14 min of USMB, 8 Gy of radiation in a separate irradiation cabinet, or combined treatments. In vivo temperature changes were collected using MR thermometry at the tumor center and far-field muscle region. Tissues specimens were collected 24 h post radiation therapy. Tumor cell death was measured and compared to untreated controls through hematoxylin and eosin staining and immunohistochemical analysis. The desired peak negative pressure of - 750 kPa used for previous USMB occurred at approximately an input power of 5 W. Temperature changes were limited to under 4 °C in ten of twelve rabbits monitored. The median temperature in the far-field muscle region of the leg was 2.50 °C for groups receiving USMB alone or in combination with radiation. Finally, statistically significant tumor cell death was demonstrated using immunohistochemical analysis in the combined therapy group compared to untreated controls. A commercial MR-guided therapy HIFU system was able to effectively treat PC3 tumors in a rabbit model using USMB therapy in combination with radiation exposures. Future work could find the use of reduced power and pressure levels in a commercial MR-guided therapy system to mechanically stimulate microbubbles and damage endothelial cells without requiring high thermal doses to elicit an antitumor response.

Target tumor therapy in human gastric cancer cells through the combination of docetaxel-loaded cationic lipid microbubbles and ultrasound-triggered microbubble destruction

It is well accepted that ultrasound-induced microbubble (USMB) cavitation is a promising method for drug delivery. Ultrasound-targeted destruction of cytotoxic drug-loaded lipid microbubbles (LMs) is used to promote the treatment of cancer. This study aimed to investigate the antitumor effects from a combination of docetaxel-loaded cationic lipid microbubbles (DLLM⁺) and ultrasound (US)-triggered microbubble destruction (UTMD) on gastric cancer (GC). It was found that the functional dose of DOC in this study was 1 × 10^-9 mol/L. We found that DLLM combined with the UTMD group showed greater growth inhibition of the cultured human gastric cancer cells (HGCCs) when compared with the other five groups by arresting the G₂/M phase in the cell cycle. However, DLLM⁺ combined with UTMD showed a higher inhibition rate of tumor growth than DLLM combined with UTMD and that of the RC/CMV-p16 combined with UTMD in vitro and in vivo experiments. DLLM⁺ combined with UTMD significantly suppressed proliferation and promoted the apoptosis of HGCCs with more cells arrested in the G₂/M phase. In addition, DLLM⁺ combined with UTMD suppressed the proliferation and induced apoptosis by arresting cells in the G₂/M phase, which led to a great inhibition of GC progression. Thus, our results indicated that the combination of DLLM⁺ and UTMD might represent a novel and promising approach to chemotherapy for GC.

Focused Ultrasound and Ultrasound Stimulated Microbubbles in Radiotherapy Enhancement for Cancer Treatment

Radiation therapy (RT) has been the standard of care for treating a multitude of cancer types. However, ionizing radiation has adverse short and long-term side effects which have resulted in treatment complications for decades. Thus, advances in enhancing the effects of RT have been the primary focus of research in radiation oncology. To avoid the usage of high radiation doses, treatment modalities such as high-intensity focused ultrasound can be implemented to reduce the radiation doses required to destroy cancer cells. In the past few years, the use of focused ultrasound (FUS) has demonstrated immense success in a number of applications as it capitalizes on spatial specificity. It allows ultrasound energy to be delivered to a targeted focal area without harming the surrounding tissue. FUS combined with RT has specifically demonstrated experimental evidence in its application resulting in enhanced cell death and tumor cure. Ultrasound-stimulated microbubbles have recently proved to be a novel way of enhancing RT as a radioenhancing agent on its own, or as a delivery vector for radiosensitizing agents such as oxygen. In this mini-review article, we discuss the bio-effects of FUS and RT in various preclinical models and highlight the applicability of this combined therapy in clinical settings.

Evaluating the effects of radiation and acoustically-stimulated microbubble therapy in an in vivo breast cancer model

Ultrasound-stimulated microbubbles (USMB) cause localized vascular effects and sensitize tumors to radiation therapy (XRT). We investigated acoustic parameter optimization for combining USMB and XRT. We treated breast cancer xenograft tumors with 500 kHz pulsed ultrasound at varying pressures (570 or 740 kPa), durations (1 to 10 minutes), and microbubble concentrations (0.01 to 1% (v/v)). Radiation therapy (2 Gy) was administered immediately or after a 6-hour delay. Histological staining of tumors 24 hours after treatment detected changes in cell morphology, cell death, and microvascular density. Significant cell death resulted at 570 kPa after a 1-minute exposure with 1% (v/v) microbubbles with or without XRT. However, significant microvascular disruption required higher ultrasound pressure and exposure duration greater than 5 minutes. Introducing a 6-hour delay between treatments (USMB and XRT) showed a similar tumor effect with no further improvement in response as compared to when XRT was delivered immediately after USMB.

Acid Sphingomyelinase Inhibitor, Imipramine, Reduces Hippocampal Neuronal Death after Traumatic Brain Injury

Traumatic brain injury (TBI) broadly degrades the normal function of the brain after a bump, blow, or jolt to the head. TBI leads to the aggravation of pre-existing brain dysfunction and promotes neurotoxic cascades that involve processes such as oxidative stress, loss of dendritic arborization, and zinc accumulation. Acid sphingomyelinase (ASMase) is an enzyme that hydrolyzes sphingomyelin to ceramide in cells. Under normal conditions, ceramide plays an important role in various physiological functions, such as differentiation and apoptosis. However, under pathological conditions, excessive ceramide production is toxic and activates the neuronal-death pathway. Therefore, we hypothesized that the inhibition of ASMase activity by imipramine would reduce ceramide formation and thus prevent TBI-induced neuronal death. To test our hypothesis, an ASMase inhibitor, imipramine (10 mg/kg, i.p.), was administrated to rats immediately after TBI. Based on the results of this study, we confirmed that imipramine significantly reduced ceramide formation, dendritic loss, oxidative stress, and neuronal death in the TBI-imipramine group compared with the TBI-vehicle group. Additionally, we validated that imipramine prevented TBI-induced cognitive dysfunction and the modified neurological severity score. Consequently, we suggest that ASMase inhibition may be a promising therapeutic strategy to reduce hippocampal neuronal death after TBI.

Effect of Ultrasound-Stimulated Microbubbles and Hyperthermia on Tumor Vasculature of Breast Cancer Xenograft

OBJECTIVE

The objective of the present study was to investigate the treatment effects of ultrasound-stimulated microbubbles (USMB) and hyperthermia (HT) on breast tumor vasculature.

METHODS

Tumor-bearing mice with breast cancer xenografts (MDA-MB-231), were exposed to different treatment conditions consisting of control (no treatment), USMB alone, HT alone, USMB with HT exposures of 10 and 50 minutes. Quantitative 3D Doppler ultrasound and photoacoustic imaging were used to detect tumor blood flow and oxygen saturation, respectively. In addition, histopathological analysis including TUNEL staining for cell death, and CD31 staining for the vessel count, was performed to complement the results of power Doppler and photoacoustic imaging.

RESULTS

Results demonstrated a decrease in tumor blood flow as well as oxygenation level following 50 minutes HT treatment either alone or combined with USMB. In contrast, 10 minutes HT alone or combined with USMB had minimal effects on blood flow and tumor oxygenation level. Treatment with HT for 50 minutes caused drops in tumor oxygenation, which were not evident with USMB treatment alone. Additionally, results revealed an increase in cell death after 10 minutes HT with or without USMB and a decrease in vessel count compared to control. Unlike previous studies which demonstrated synergistic treatment effects combining USMB with other modalities such as radiation or chemotherapy, USMB and HT effects were not synergistic in the present study.

CONCLUSION

The results here demonstrated HT and USMB both alone or together resulted in a significant reduction in tumor blood flow, tumor oxygenation, and vessel count with observed increases in cell death response.

Emerging Roles of Ceramides in Breast Cancer Biology and Therapy

One of the classic hallmarks of cancer is the imbalance between elevated cell proliferation and reduced cell death. Ceramide, a bioactive sphingolipid that can regulate this balance, has long been implicated in cancer. While the effects of ceramide on cell death and therapeutic efficacy are well established, emerging evidence indicates that ceramide turnover to downstream sphingolipids, such as sphingomyelin, hexosylceramides, sphingosine-1-phosphate, and ceramide-1-phosphate, is equally important in driving pro-tumorigenic phenotypes, such as proliferation, survival, migration, stemness, and therapy resistance. The complex and dynamic sphingolipid network has been extensively studied in several cancers, including breast cancer, to find key sphingolipidomic alterations that can be exploited to develop new therapeutic strategies to improve patient outcomes. Here, we review how the current literature shapes our understanding of how ceramide synthesis and turnover are altered in breast cancer and how these changes offer potential strategies to improve breast cancer therapy.

Tumoral Oxygenation and Biodistribution of Lonidamine Oxygen Microbubbles Following Localized Ultrasound-Triggered Delivery

Prior work has shown that microbubble-assisted delivery of oxygen improves tumor oxygenation and radiosensitivity, albeit over a limited duration. Lonidamine (LND) has been investigated because of its ability to stimulate glycolysis, lactate production, inhibit mitochondrial respiration, and inhibit oxygen consumption rates in tumors but suffers from poor bioavailability. The goal of this work was to characterize LND-loaded oxygen microbubbles and assess their ability to oxygenate a human head and neck squamous cell carcinoma (HNSCC) tumor model, while also assessing LND biodistribution. In tumors treated with surfactant-shelled microbubbles with oxygen core (SE61O₂) and ultrasound, pO₂ levels increased to a peak 19.5±9.7 mmHg, 50 seconds after injection and returning to baseline after 120 seconds. In comparison, in tumors treated with SE61O₂/LND and ultrasound, pO₂ levels showed a peak increase of 29.0±8.3 mmHg, which was achieved 70 seconds after injection returning to baseline after 300 seconds (p<0.001). The co-delivery of O₂andLNDvia SE61 also showed an improvement of LND biodistribution in both plasma and tumor tissues (p<0.001). In summary, ultrasound-sensitive microbubbles loaded with O₂ and LND provided prolonged oxygenation relative to oxygenated microbubbles alone, as well as provided an ability to locally deliver LND, making them more appropriate for clinical translation.

Synergistic enhancement of cell death by triple combination therapy of docetaxel, ultrasound and microbubbles, and radiotherapy on PC3 a prostate cancer cell line

The application of ultrasound and microbubbles (USMB) has been shown to enhance both chemotherapy and radiotherapy. This study investigated the potential of triple combination therapy comprised of USMB, docetaxel (Taxotere: TXT) chemotherapy and XRT to enhance treatment efficacy. Prostate cancer (PC3) cells in suspension were treated with various combinations of USMB, chemotherapy and radiotherapy. Cells were treated with ultrasound and microbubbles (500 kHz pulse center frequency, 580 kPa peak negative pressure, 10 μs pulse duration, 60 s insonation time and 2% Definity microbubbles (v/v)), XRT (2 Gy), and Taxotere (TXT) at concentrations ranging from 0.001 to 0.1 nM for 5- and 120-minutes duration. Following treatment, cell viability was assessed using a clonogenic assay. Therapeutic efficiency of the combined treatments depended on chemotherapy and microbubble exposure conditions. Under the exposure conditions of the study, the triple combination therapy synergistically enhanced clonogenic cell death compared to single and double combination therapy. Cell viability of ∼2% was achieved with the triple combination therapy corresponding to ∼29, ∼37, and ∼38 folds decrease compared to XRT (57%), USMB (74%) and TXT (76%) alone conditions, respectively. In addition, the triple combination therapy decreased cell viability by ∼29, ∼19- and ∼11 folds compared to TXT_2hr + USMB (58%), TXT_2hr + XRT (37%), and USMB + XRT (22%), respectively. The in vivo PC3 tumours showed that USMB significantly enhanced cell death through detection of apoptosis (TUNEL) with both TXT and TXT + XRT. The study demonstrated that the triple combination therapy can significantly enhance cell death in prostate cancer cells both in vitro and in vivo under relatively low chemotherapy and ionizing radiation doses.

Metabonomic analysis of abnormal sphingolipid metabolism in rheumatoid arthritis synovial fibroblasts in hypoxia microenvironment and intervention of geniposide

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by a joint hypoxia microenvironment. Our previous untargeted metabolomics study found that sphingolipid (SPL) metabolism was abnormal in the joint synovial fluid samples from adjuvant arthritis (AA) rats. Geniposide (GE), an iridoid glycoside component of the dried fruit of Gardenia jasminoides Ellis, is commonly used for RA treatment in many Asian countries. At present, the mechanism of GE in the treatment of RA, especially in the joint hypoxia microenvironment, is not entirely clear from the perspective of SPL metabolism. The purpose of this research was to explore the potential mechanism of abnormal SPL metabolism in RA joint hypoxia microenvironment and the intervention effect of GE, through the untargeted metabolic analysis based on the ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). Arthritis index, foot swelling and histopathology were used to assess whether the AA rat model was successfully established. The SPLs extracts collected from AA rats’ synovial tissue, serum and rheumatoid arthritis synovial fibroblasts (RASFs, MH7A cells, hypoxia/normoxia culture) were analyzed by metabolomics and lipdomics approach based on UPLC-Q-TOF/MS, to identify potential biomarkers associated with disorders of GE regulated RA sphingolipid metabolism. As a result, 11 sphingolipid metabolites related to RA were screened and identified. Except for galactosylceramide (d18:1/20:0), GE could recover the change levels of the above 10 sphingolipid biomarkers in varying degrees. Western blotting results showed that the changes in ceramide (Cer) level regulated by GE were related to the down-regulation of acid-sphingomyelinase (A-SMase) expression in synovial tissue of AA rats. To sum up, this research examined the mechanism of GE in the treatment of RA from the perspective of SPL metabolism and provided a new strategy for the screening of biomarkers for clinical diagnosis of RA.

Involvement of Ceramide Signalling in Radiation-Induced Tumour Vascular Effects and Vascular-Targeted Therapy

Sphingolipids are well-recognized critical components in several biological processes. Ceramides constitute a class of sphingolipid metabolites that are involved in important signal transduction pathways that play key roles in determining the fate of cells to survive or die. Ceramide accumulated in cells causes apoptosis; however, ceramide metabolized to sphingosine promotes cell survival and angiogenesis. Studies suggest that vascular-targeted therapies increase endothelial cell ceramide resulting in apoptosis that leads to tumour cure. Specifically, ultrasound-stimulated microbubbles (USMB) used as vascular disrupting agents can perturb endothelial cells, eliciting acid sphingomyelinase (ASMase) activation accompanied by ceramide release. This phenomenon results in endothelial cell death and vascular collapse and is synergistic with other antitumour treatments such as radiation. In contrast, blocking the generation of ceramide using multiple approaches, including the conversion of ceramide to sphingosine-1-phosphate (S1P), abrogates this process. The ceramide-based cell survival "rheostat" between these opposing signalling metabolites is essential in the mechanotransductive vascular targeting following USMB treatment. In this review, we aim to summarize the past and latest findings on ceramide-based vascular-targeted strategies, including novel mechanotransductive methodologies.

Application of Ultrasound Combined with Microbubbles for Cancer Therapy

At present, cancer is one of the leading causes of death worldwide. Treatment failure remains one of the prime hurdles in cancer treatment due to the metastatic nature of cancer. Techniques have been developed to hinder the growth of tumours or at least to stop the metastasis process. In recent years, ultrasound therapy combined with microbubbles has gained immense success in cancer treatment. Ultrasound-stimulated microbubbles (USMB) combined with other cancer treatments including radiation therapy, chemotherapy or immunotherapy has demonstrated potential improved outcomes in various in vitro and in vivo studies. Studies have shown that low dose radiation administered with USMB can have similar effects as high dose radiation therapy. In addition, the use of USMB in conjunction with radiotherapy or chemotherapy can minimize the toxicity of high dose radiation or chemotherapeutic drugs, respectively. In this review, we discuss the biophysical properties of USMB treatment and its applicability in cancer therapy. In particular, we highlight important preclinical and early clinical findings that demonstrate the antitumour effect combining USMB and other cancer treatment modalities (radiotherapy and chemotherapy). Our review mainly focuses on the tumour vascular effects mediated by USMB and these cancer therapies. We also discuss several current limitations, in addition to ongoing and future efforts for applying USMB in cancer treatment.

Ultrasound-stimulated microbubbles contributes to radiotherapy in esophageal carcinoma

This study aimed to explore the effect of ultrasound-stimulated microbubbles (USMBs) on tumor radiosensitivity in esophageal carcinoma (EC). The human EC cell line KYSE-510 and human umbilical vein endothelial cells (HUVECs) were exposed to radiation alone or in combination with USMBs. CCK-8, colony formation, and EdU assays were used to determine cell viability and proliferation. Cell apoptosis was assessed using flow cytometry. Cell migration and invasion were examined by wound healing and transwell assays. Western blotting showed that the protein levels were associated with apoptosis, epithelial-mesenchymal transition (EMT), and angiogenesis. An endothelial tube-forming assay was used to detect the angiogenic activity of HUVECs. Xenograft experiments were used to examine the effect of USMBs on EC radiosensitivity in vivo. The expression of Ki-67 in tumors was detected using immunohistochemistry. USMBs enhanced the suppressive effect of radiation on proliferation, migration, invasion, and EMT, and promoted radiation-induced apoptosis in EC cells in vitro. Angiogenesis in EC was suppressed by radiation and further inhibited by the combination of radiation and USMBs. In vivo experiments revealed that USMBs increased the radiosensitivity of ECs to tumor growth. Collectively, USMBs enhanced the effects of radiotherapy in esophageal carcinoma.

Emerging Applications of Ultrasound-Contrast Agents in Radiation Therapy

Radiation therapy (RT) causes DNA damage through ionization, leading to double-strand breaks. In addition, it generates reactive oxygen species (ROS), which are toxic to tumor cells and the vasculature. However, hypoxic regions in the tumor have been shown to not only decrease treatment response but also increase the likelihood of recurrence and metastasis. Ultrasound-sensitive micro-bubbles are emerging as a useful diagnostic and therapeutic tool within RT. Contrast-enhanced ultrasound (CEUS) has shown great promise in early prediction of tumor response to RT. Ultrasound-triggered micro-bubble cavitation has also been shown to induce bio-effects that can sensitize angiogenic tumor vessels to RT. Additionally, ultrasound can trigger the release of drugs from micro-bubble carriers via localized micro-bubble destruction. This approach has numerous applications in RT, including targeted oxygen delivery before radiotherapy. Furthermore, micro-bubbles can be used to locally create ROS without radiation. Sonodynamic therapy uses focused ultrasound and a sonosensitizer to selectively produce ROS in the tumor region and has been explored as a treatment option for cancer. This review summarizes emerging applications of ultrasound contrast agents in RT and ROS augmentation.

Physiological functions and therapeutic applications of neutral sphingomyelinase and acid sphingomyelinase

Sphingomyelin (SM) can be converted into ceramide (Cer) by neutral sphingomyelinase (NSM) and acid sphingomyelinase (ASM). Cer is a second messenger of lipids and can regulate cell growth and apoptosis. Increasing evidence shows that NSM and ASM play key roles in many processes, such as apoptosis, immune function and inflammation. Therefore, NSM and ASM have broad prospects in clinical treatments, especially in cancer, cardiovascular diseases (such as atherosclerosis), nervous system diseases (such as Alzheimer's disease), respiratory diseases (such as chronic obstructive pulmonary disease) and the phenotype of dwarfisms in adolescents, playing a complex regulatory role. This review focuses on the physiological functions of NSM and ASM and summarizes their roles in certain diseases and their potential applications in therapy.

Ultrasound-Mediated Gemcitabine Delivery Reduces the Normal-Tissue Toxicity of Chemoradiation Therapy in a Muscle-Invasive Bladder Cancer Model

PURPOSE

Chemoradiation therapy is the standard of care in muscle-invasive bladder cancer (MIBC). Although agents such as gemcitabine can enhance tumor radiosensitivity, their side effects can limit patient eligibility and treatment efficacy. This study investigates ultrasound and microbubbles for targeting gemcitabine delivery to reduce normal-tissue toxicity in a murine orthotopic MIBC model.

MATERIALS AND METHODS

CD1-nude mice were injected orthotopically with RT112 bladder tumor cells. Conventional chemoradiation involved injecting gemcitabine (10 mg/kg) before 6 Gy targeted irradiation of the bladder area using the Small Animal Radiation Research Platform (SARRP). Ultrasound-mediated gemcitabine delivery (10 mg/kg gemcitabine) involved either coadministration of microbubbles with gemcitabine or conjugating gemcitabine onto microbubbles followed by exposure to ultrasound (1.1 MHz center frequency, 1 MPa peak negative pressure, 1% duty cycle, and 0.5 Hz pulse repetition frequency) before SARRP irradiation. The effect of ultrasound and microbubbles alone was also tested. Tumor volumes were measured by 3D ultrasound imaging. Acute normal-tissue toxicity from 12 Gy to the lower bowel area was assessed using an intestinal crypt assay in mice culled 3.75 days posttreatment.

RESULTS

A significant delay in tumor growth was observed with conventional chemoradiation therapy and both microbubble groups (P < .05 compared with the radiation-only group). Transient weight loss was seen in the microbubble groups, which resolved within 10 days posttreatment. A positive correlation was found between weight loss on day 3 posttreatment and tumor growth delay (P < .05; R2 = 0.76). In contrast with conventional chemoradiation therapy, ultrasound-mediated drug delivery methods did not exacerbate the acute intestinal toxicity using the crypt assay.

CONCLUSIONS

Ultrasound and microbubbles offer a promising new approach for improving chemoradiation therapy for muscle-invasive bladder cancer, maintaining a delay in tumor growth but with reduced acute intestinal toxicity compared with conventional chemoradiation therapy.

Using ultrasound-targeted microbubble destruction to enhance radiotherapy of glioblastoma

OBJECTIVE

To investigate the efficacy and mechanism of ultrasound-targeted microbubble destruction (UTMD) combined with radiotherapy (XRT) on glioblastoma.

METHODS

The enhanced radiosensitization by UTMD was assessed through colony formation and cell apoptosis in Human glioblastoma cells (U87MG). Subcutaneous transplantation tumors in 24 nude mice implanted with U87MG cells were randomly assigned to 4 different treatment groups (Control, UTMD, XRT, and UTMD + XRT) based on tumor sizes (100-300 mm³). Tumor growth was observed for 10 days after treatment, and then histopathology stains (HE, CD34, and γH2AX) were applied to the tumor samples. A TUNEL staining experiment was applied to detect the apoptosis rate of mice tumor samples. Meanwhile, tissue proteins were extracted from animal specimens, and the expressions of dsDNA break repair-related proteins from animal specimens were examined by the western blot.

RESULTS

When the radiotherapy dose was 4 Gy, the colony formation rate of U87MG cells in the UTMD + XRT group was 32 ± 8%, lower than the XRT group (54 ± 14%, p < 0.01). The early apoptotic rate of the UTMD + XRT group was 21.1 ± 3% at 48 h, higher than that of the XRT group (15.2 ± 4%). The tumor growth curve indicated that the tumor growth was inhibited in the UTMD + XRT group compared with other groups during 10 days of observation. In TUNEL experiment, the apoptotic cells of the UTMD + XRT group were higher than that of the XRT group (p < 0.05). The UTMD + XRT group had the lowest MVD value, but was not significantly different from other groups (p > 0.05). In addition, γH2AX increased due to the addition of UTMD to radiotherapy compared to XRT in immunohistochemistry (p < 0.05).

CONCLUSIONS

Our study clearly demonstrated the enhanced destructive effect of UTMD combined with 4 Gy radiotherapy on glioblastoma. This could be partly achieved by the increased ability of DNA damage of tumor cells.

US-triggered Microbubble Destruction for Augmenting Hepatocellular Carcinoma Response to Transarterial Radioembolization: A Randomized Pilot Clinical Trial

Background US contrast agents are gas-filled microbubbles (MBs) that can be locally destroyed by using external US. Among other bioeffects, US-triggered MB destruction, also known as UTMD, has been shown to sensitize solid tumors to radiation in preclinical models through localized insult to the vascular endothelial cells. Purpose To evaluate the safety and preliminary efficacy of combining US-triggered MB destruction and transarterial radioembolization (TARE) in participants with hepatocellular carcinoma (HCC). Materials and Methods In this pilot clinical trial, participants with HCC scheduled for sublobar TARE were randomized to undergo either TARE or TARE with US-triggered MB destruction 1-4 hours and approximately 1 and 2 weeks after TARE. Enrollment took place between July 2017 and February 2020. Safety of US-triggered MB destruction was evaluated by physiologic monitoring, changes in liver function tests, adverse events, and radiopharmaceutical distribution. Treatment efficacy was evaluated by using modified Response Evaluation Criteria in Solid Tumors (mRECIST) on cross-sectional images, time to required next treatment, transplant rates, and overall survival. Differences across mRECIST reads were compared by using a Mann-Whitney U test, and the difference in prevalence of tumor response was evaluated by Fisher exact test, whereas differences in time to required next treatment and overall survival curves were compared by using a log-rank (Mantel-Cox) test. Results Safety results from 28 participants (mean age, 70 years ± 10 [standard deviation]; 17 men) demonstrated no significant changes in temperature (P = .31), heart rate (P = .92), diastolic pressure (P = .31), or systolic pressure (P = .06) before and after US-triggered MB destruction. No changes in liver function tests between treatment arms were observed 1 month after TARE (P > .15). Preliminary efficacy results showed a greater prevalence of tumor response (14 of 15 [93%; 95% CI: 68, 100] vs five of 10 [50%; 95% CI: 19, 81]; P = .02) in participants who underwent both US-triggered MB destruction and TARE (P = .02). Conclusion The combination of US-triggered microbubble destruction and transarterial radioembolization is feasible with an excellent safety profile in this patient population and appears to result in improved hepatocellular carcinoma treatment response. © RSNA, 2020.

Ultrasound-stimulated microbubble radiation enhancement of tumors: Single-dose and fractionated treatment evaluation

The use of ultrasound-stimulated microbubble therapy has successfully been used to target tumor vasculature and enhance the effects of radiation therapy in tumor xenografts in mice. Here, we further investigate this treatment using larger, more clinically relevant tumor models. New Zealand white rabbits bearing prostate tumor (PC3) xenografts received a single treatment of either ultrasound-stimulated microbubbles (USMB), ionizing radiation (XRT; 8Gy), or a combination of both treatments (USMB+XRT). Treatment outcome was evaluated 24 hours after treatment using histopathology, immunolabeling, 3D Doppler ultrasound and photoacoustic imaging. A second cohort of rabbits received multiple treatments over a period of three weeks, where USMB treatments were delivered twice weekly with daily XRT treatments to deliver a fractionated 2Gy dose five days per week. A significant decrease in vascular function, observed through immunolabeling of vascular endothelial cells, was observed in tumors receiving the combined treatment (USMB+XRT) compared to control and single treatment groups. This was associated with an increase in cell death as observed through in situ end labeling (ISEL), a decrease in vascular index measured by Power Doppler imaging, and a decrease in oxygen saturation. In rabbits undergoing the long-term fractionated combined treatment, a significant growth delay was observed after 1 week and a significant reduction in tumor size was observed after 3 weeks with combined therapy. Results demonstrated an enhancement of radiation effect and superior anti-tumor effect of the combination of USMB+XRT compared to the single treatments alone. Tumor growth was maximally inhibited with fractionated radiotherapy combined with the ultrasound-stimulated microbubble-based therapy.

Inhibitors of Ceramide- and Sphingosine-Metabolizing Enzymes as Sensitizers in Radiotherapy and Chemotherapy for Head and Neck Squamous Cell Carcinoma

In the treatment of advanced head and neck squamous cell carcinoma (HNSCC), including oral SCC, radiotherapy is a commonly performed therapeutic modality. The combined use of radiotherapy with chemotherapy improves therapeutic effects, but it also increases adverse events. Ceramide, a central molecule in sphingolipid metabolism and signaling pathways, mediates antiproliferative responses, and its level increases in response to radiotherapy and chemotherapy. However, when ceramide is metabolized, prosurvival factors, such as sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and glucosylceramide, are produced, reducing the antitumor effects of ceramide. The activities of ceramide- and sphingosine-metabolizing enzymes are also associated with radio- and chemo-resistance. Ceramide analogs and low molecular-weight compounds targeting these enzymes exert anticancer effects. Synthetic ceramides and a therapeutic approach using ultrasound have also been developed. Inhibitors of ceramide- and sphingosine-metabolizing enzymes and synthetic ceramides can function as sensitizers of radiotherapy and chemotherapy for HNSCC.

Sphingosine-1-phosphate alleviates irradiation-induced parotid injury in a miniature pig model

OBJECTIVES

Our aim was to verify the alleviation effect of sphingosine-1-phosphate (S1P) in a miniature pig model.

MATERIAL AND METHODS

Thirty male miniature pigs were randomly separated into 10 groups in our experiment. We administered S1P through the parotid duct in a retrograde fashion 2 hr before irradiation (IR). The salivary flow rate and blood flow rate were tested 20 weeks after IR. The apoptotic level was checked at 12, 24 hr and 7 days post-IR.

RESULTS

Twenty weeks after IR, the salivary flow rate of the IR-side parotid gland in IR + S1P group can be maintained at about 40% of the non-IR side, while only 20% was maintained in the IR group. The blood flow rate and microvascular density were significantly higher in the IR + S1P group than in the IR group. The apoptotic level and cleaved caspase-3 expression were downregulated in IR + S1P group, and the ratio of Bcl-2/Bax was increased. The blood flow rate and CD31 level were significantly restored at 12, 24 hr and 7 days post-IR.

CONCLUSION

Sphingosine-1-phosphate may partially alleviate IR-induced parotid dysfunction by decreasing apoptosis of microvascular endothelial cells and maintaining the blood flow rate.

Ultrasound microbubble potentiated enhancement of hyperthermia-effect in tumours

It is now well established that for tumour growth and survival, tumour vasculature is an important element. Studies have demonstrated that ultrasound-stimulated microbubble (USMB) treatment causes extensive endothelial cell death leading to tumour vascular disruption. The subsequent rapid vascular collapse translates to overall increases in tumour response to various therapies. In this study, we explored USMB involvement in the enhancement of hyperthermia (HT) treatment effects. Human prostate tumour (PC3) xenografts were grown in mice and were treated with USMB, HT, or with a combination of the two treatments. Treatment parameters consisted of ultrasound pressures of 0 to 740 kPa, the use of perfluorocarbon-filled microbubbles administered intravenously, and an HT temperature of 43°C delivered for various times (0–50 minutes). Single and multiple repeated treatments were evaluated. Tumour response was monitored 24 hours after treatments and tumour growth was monitored for up to over 30 days for a single treatment and 4 weeks for multiple treatments. Tumours exposed to USMB combined with HT exhibited enhanced cell death (p<0.05) and decreased vasculature (p<0.05) compared to untreated tumours or those treated with either USMB alone or HT alone within 24 hours. Deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) staining and cluster of differentiation 31 (CD31) staining were used to assess cell death and vascular content, respectively. Further, tumours receiving a single combined USMB and HT treatment exhibited decreased tumour volumes (p<0.05) compared to those receiving either treatment alone when monitored over the duration of 30 days. Additionally, tumour response monitored weekly up to 4 weeks demonstrated a reduced vascular index and tumour volume, increased fibrosis and lesser number of proliferating cells with combined treatment of USMB and HT. Thus in this study, we characterize a novel therapeutic approach that combines USMB with HT to enhance treatment responses in a prostate cancer xenograft model in vivo.

Sphingolipid metabolism and drug resistance in ovarian cancer

Despite progress in understanding molecular aberrations that contribute to the development and progression of ovarian cancer, virtually all patients succumb to drug resistant disease at relapse. Emerging data implicate bioactive sphingolipids and regulation of sphingolipid metabolism as components of response to chemotherapy or development of resistance. Increases in cytosolic ceramide induce apoptosis in response to therapy with multiple classes of chemotherapeutic agents. Aberrations in sphingolipid metabolism that accelerate the catabolism of ceramide or that prevent the production and accumulation of ceramide contribute to resistance to standard of care platinum- and taxane-based agents. The aim of this review is to highlight current literature and research investigating the influence of the sphingolipids and enzymes that comprise the sphingosine-1-phosphate pathway on the progression of ovarian cancer. The focus of the review is on the utility of sphingolipid-centric therapeutics as a mechanism to circumvent drug resistance in this tumor type.

Radiation, inflammation and the immune response in cancer

Radiation is an important component of cancer treatment with more than half of all patients receive radiotherapy during their cancer experience. While the impact of radiation on tumour morphology is routinely examined in the pre-clinical and clinical setting, the impact of radiation on the tumour microenvironment and more specifically the inflammatory/immune response is less well characterised. Inflammation is a key contributor to short- and long-term cancer eradication, with significant tumour and normal tissue consequences. Therefore, the role of radiation in modulating the inflammatory response is highly topical given the current wave of targeted and immuno-therapeutic treatments for cancer. This review provides a general overview of how radiation modulates the inflammatory and immune response—(i) how radiation induces the inflammatory/immune system, (ii) the cellular changes that take place, (iii) how radiation dose delivery affects the immune response, and (iv) a discussion on research directions to improve patient survival, reduce side effects, improve quality of life, and reduce financial costs in the immediate future. Harnessing the benefits of radiation on the immune response will enhance its maximal therapeutic benefit and reduce radiation-induced toxicity.