Suppressive effects of a proton beam on tumor growth and lung metastasis through the inhibition of metastatic gene expression in 4T1 orthotopic breast cancer model

Models for Translational Proton Radiobiology-From Bench to Bedside and Back

The number of proton therapy centers worldwide are increasing steadily, with more than two million cancer patients treated so far. Despite this development, pending questions on proton radiobiology still call for basic and translational preclinical research. Open issues are the on-going discussion on an energy-dependent varying proton RBE (relative biological effectiveness), a better characterization of normal tissue side effects and combination treatments with drugs originally developed for photon therapy. At the same time, novel possibilities arise, such as radioimmunotherapy, and new proton therapy schemata, such as FLASH irradiation and proton mini-beams. The study of those aspects demands for radiobiological models at different stages along the translational chain, allowing the investigation of mechanisms from the molecular level to whole organisms. Focusing on the challenges and specifics of proton research, this review summarizes the different available models, ranging from in vitro systems to animal studies of increasing complexity as well as complementing in silico approaches.

Oral Delivery of Gambogenic Acid by Functional Polydopamine Nanoparticles for Targeted Tumor Therapy

To enhance the water solubility, oral bioavailability, and tumor targeting of gambogenic acid (GNA), polydopamine nanoparticles (PDA NPs) were prepared to encapsulate and stabilize GNA surface modified by folic acid (FA) and then coated with sodium alginate (GNA@PDA-FA SA NPs) to achieve an antitumor effect by oral administration. GNA@PDA-FA SA NPs exhibited in vitro pH-sensitive release behavior. In vitro cell studies manifested that GNA@PDA-FA NPs had higher cytotoxicity to 4T1 cells compared with raw GNA (IC₅₀ = 2.58 μM vs 7.57 μM). After being modified with FA, GNA@PDA-FA NPs were taken up easily by 4T1 cells. In vivo studies demonstrated that the area under the curve (AUC_0→∞) of the plasma drug concentration-time of GNA@PDA-FA SA NPs was 2.97-fold higher than that of raw GNA, along with improving drug distribution in the liver, lung, and kidney tissues. In vivo anti-tumor experiments, GNA@PDA-FA SA NPs significantly inhibited the growth of breast tumors in the 4T1 xenograft breast cancer model via oral administration without obvious toxicity on major organs. Our studies indicated that the GNA@PDA-FA SA NPs modified with FA and coated with SA were a promising drug delivery system for targeting tumor therapy via oral administration.

Combination Therapy With Charged Particles and Molecular Targeting: A Promising Avenue to Overcome Radioresistance

Radiotherapy plays a central role in the treatment of cancer patients. Over the past decades, remarkable technological progress has been made in the field of conventional radiotherapy. In addition, the use of charged particles (e.g., protons and carbon ions) makes it possible to further improve dose deposition to the tumor, while sparing the surrounding healthy tissues. Despite these improvements, radioresistance and tumor recurrence are still observed. Although the mechanisms underlying resistance to conventional radiotherapy are well-studied, scientific evidence on the impact of charged particle therapy on cancer cell radioresistance is restricted. The purpose of this review is to discuss the potential role that charged particles could play to overcome radioresistance. This review will focus on hypoxia, cancer stem cells, and specific signaling pathways of EGFR, NFκB, and Hedgehog as well as DNA damage signaling involving PARP, as mechanisms of radioresistance for which pharmacological targets have been identified. Finally, new lines of future research will be proposed, with a focus on novel molecular inhibitors that could be used in combination with charged particle therapy as a novel treatment option for radioresistant tumors.

Patterns of protein expression in human head and neck cancer cell lines differ after proton vs photon radiotherapy

BACKGROUND

Proton radiotherapy (PRT) may be a less toxic alternative to photon radiotherapy (XRT) for patients with head and neck squamous cell carcinoma (HNSCC). However, the molecular responses of HNSCC cells to PRT vs XRT are unclear.

METHODS

Proteomics analyses of protein expression profiles by reverse-phase protein arrays were done for two human papillomavirus [HPV]-negative and two HPV+ cell lines. Expression patterns of 175 proteins involved in several signaling pathways were tested.

RESULTS

Compared with PRT, XRT tended to induce lower expression of DNA damage repair-and cell cycle arrest-related proteins and higher expression of cell survival- and proliferation-related proteins.

CONCLUSIONS

Under these experimental conditions, PRT and XRT induced different protein expression and activation profiles. Further preclinical verification is needed, as are studies of tumor pathway mutations as biomarkers for choice of treatment or as radiosensitization targets to improve the response of HNSCC to PRT or XRT.

Inhibition of TPA‑induced metastatic potential by morin hydrate in MCF‑7 human breast cancer cells via the Akt/GSK‑3β/c‑Fos signaling pathway

Plant flavonoid 2',3,4',5,7‑pentahydroxyflavone (morin hydrate), isolated from the family Moraceae (Morus alba L.), is known to have anti‑inflammatory and anticancer effects. However, its pharmaceutical effects on metastasis have not been fully elucidated to date. Therefore, the current study investigated the effects of morin hydrate on cancer metastasis in MCF‑7 human breast cancer cells. The results showed that morin hydrate suppressed 12‑O‑tetradecanoylphorbol‑13‑acetate (TPA)‑induced cell migration and invasion via the inhibition of matrix metalloproteinase (MMP)‑9 activity. Furthermore, gene expression level of MMP‑9, MMP‑7, urokinase plasminogen activator (uPA), uPA receptor (uPAR) and fibronectin were significantly decreased by morin hydrate treatment. Morin hydrate inhibited the phosphorylation of Akt and glycogen synthase kinase (GSK)‑3β, and downregulated the expression of an activator protein‑1 subunit c‑Fos. In addition, the GSK‑3β phosphorylation and c‑Fos expression were suppressed by PI3K/Akt pathway inhibitors, LY294002 and wortmannin. Taken together, these results demonstrated that morin hydrate reduced the metastatic potential in TPA‑treated MCF‑7 human breast cancer cells via the inhibition of MMPs, uPA and uPAR, and the underlying Akt/GSK‑3β/c‑Fos pathway. Therefore, the present investigation suggested that morin hydrate may be a natural substance with a preventive potential for metastasis in breast cancer cells.

The Combination of Particle Irradiation With the Hedgehog Inhibitor GANT61 Differently Modulates the Radiosensitivity and Migration of Cancer Cells Compared to X-Ray Irradiation

Due to the advantages of charged particles compared to conventional radiotherapy, a vast increase is noted in the use of particle therapy in the clinic. These advantages include an improved dose deposition and increased biological effectiveness. Metastasis is still an important cause of mortality in cancer patients and evidence has shown that conventional radiotherapy can increase the formation of metastasizing cells. An important pathway involved in the process of metastasis is the Hedgehog (Hh) signaling pathway. Recent studies have demonstrated that activation of the Hh pathway, in response to X-rays, can lead to radioresistance and increased migratory, and invasive capabilities of cancer cells. Here, we investigated the effect of X-rays, protons, and carbon ions on cell survival, migration, and Hh pathway gene expression in prostate cancer (PC3) and medulloblastoma (DAOY) cell lines. In addition, the potential modulation of cell survival and migration by the Hh pathway inhibitor GANT61 was investigated. We found that in both cell lines, carbon ions were more effective in decreasing cell survival and migration as well as inducing more significant alterations in the Hh pathway genes compared to X-rays or protons. In addition, we show here for the first time that the Hh inhibitor GANT61 is able to sensitize DAOY medulloblastoma cells to particle radiation (proton and carbon ion) but not to conventional X-rays. This important finding demonstrates that the results of combination treatment strategies with X-ray radiotherapy cannot be automatically extrapolated to particle therapy and should be investigated separately. In conclusion, combining GANT61 with particle radiation could offer a benefit for specific cancer types with regard to cancer cell survival.

Cancer stem cells in radiation response: current views and future perspectives in radiation oncology

Purpose: Despite technological improvement and advances in biology-driven patient stratification, many patients still fail radiotherapy resulting in loco-regional and distant recurrence. Tumor heterogeneity remains a key challenge to effective cancer treatment, and reliable stratification of cancer patients for prediction of outcomes is highly important. Intratumoral heterogeneity is manifested at the different levels, including different tumorigenic properties of cancer cells. Since John Dick et al. isolated leukemia initiating cells in 1990, the populations of tumor initiating or cancer stem cells (CSCs) were identified and characterized also for a broad spectrum of solid tumor types. The properties of CSCs are of considerable clinical relevance: CSCs have self-renewal and tumor initiating potential, and the metastases are initiated by the CSC clones with the ability to disseminate from the primary tumor site. Conclusion: Evidence from both, experimental and clinical studies demonstrates that the probability of achieving local tumor control by radiation therapy depends on the complete eradication of CSC populations. The number, properties and molecular signature of CSCs are highly predictive for clinical outcome of radiotherapy, whereas targeted therapies against CSCs combined with conventional treatment are expected to provide an improved clinical response and prevent tumor relapse. In this review, we discuss the modern methods to study CSCs in radiation biology, the role of CSCs in personalized cancer therapy as well as future directions for CSC research in translational radiooncology.

The association of changes in RAD51 and survivin expression levels with the proton beam sensitivity of Capan‑1 and Panc‑1 human pancreatic cancer cells

Fewer than 20% of patients diagnosed with pancreatic cancer can be treated with surgical resection. The effects of proton beam irradiation were evaluated on the cell viabilities in Panc‑1 and Capan‑1 pancreatic cancer cells. The cells were irradiated with proton beams at the center of Bragg peaks with a 6‑cm width using a proton accelerator. Cell proliferation was assessed with the MTT assay, gene expression was analyzed with semi‑quantitative or quantitative reverse transcription‑polymerase chain reaction analyses and protein expression was evaluated by western blotting. The results demonstrated that Capan‑1 cells had lower cell viability than Panc‑1 cells at 72 h after proton beam irradiation. Furthermore, the cleaved poly (ADP‑ribose) polymerase protein level was increased by irradiation in Capan‑1 cells, but not in Panc‑1 cells. Additionally, it was determined that histone H2AX phosphorylation in the two cell lines was increased by irradiation. Although a 16 Gy proton beam was only slightly up‑regulated cyclin‑dependent kinase inhibitor 1 (p21) protein expression in Capan‑1 cells, p21 expression levels in Capan‑1 and Panc‑1 cells were significantly increased at 72 h after irradiation. Furthermore, it was observed that the expression of DNA repair protein RAD51 homolog 1 (RAD51), a homogenous repair enzyme, was decreased in what appeared to be a dose‑dependent manner by irradiation in Capan‑1 cells. Contrastingly, the transcription of survivin in Panc‑1 was significantly enhanced. The results suggest that RAD51 and survivin are potent markers that determine the therapeutic efficacy of proton beam therapy in patients with pancreatic cancer.