Effect of bisphosphonates and statins on the in vitro radiosensitivity of breast cancer cell lines.

BACKGROUND: Early-stage breast cancer is usually treated with breast-conserving surgery followed by adjuvant radiation therapy. Acute skin toxicity is a common radiation-induced side effect experienced by many patients. Recently, a combination of bisphosphonates (zoledronic acid) and statins (pravastatin), or ZOPRA, was shown to radio-protect normal tissues by enhancing DNA double-strand breaks (DSB) repair mechanism. However, there are no studies assessing the effect of ZOPRA on cancerous cells. The purpose of this study is to characterize the in vitro effect of the zoledronic acid (ZO), pravastatin (PRA), and ZOPRA treatment on the molecular and cellular radiosensitivity of breast cancer cell lines. MATERIALS: Two breast cancer cell lines, MDA MB 231 and MCF-7, were tested. Cells were treated with different concentrations of pravastatin (PRA), zoledronate (ZO), as well as their ZOPRA combination, before irradiation. Anti-γH2AX and anti-pATM immunofluorescence were performed to study DNA DSB repair kinetics. MTT assay was performed to assess cell proliferation and viability, and flow cytometry was performed to analyze the effect of the drugs on the cell cycle distribution. The clonogenic assay was used to assess cell survival. RESULTS: ZO, PRA, and ZOPRA treatments were shown to increase the residual number of γH2AX foci for both cell lines. ZOPRA treatment was also shown to reduce the activity of the ATM kinase in MCF-7. ZOPRA induced a significant decrease in cell survival for both cell lines. CONCLUSIONS: Our findings show that pretreatment with ZOPRA can decrease the radioresistance of breast cancer cells at the molecular and cellular levels. The fact that ZOPRA was previously shown to radioprotect normal tissues, makes it a good candidate to become a therapeutic window-widening drug.

Stereotactic Radiation Therapy of Single Brain Metastases: A Literature Review of Dosimetric Studies.

Stereotactic radiotherapy (SRT) plays a major role in treating brain metastases (BMs) and can be delivered using various equipment and techniques. This review aims to identify the dosimetric factors of each technique to determine whether one should be preferred over another for single BMs treatment. A systematic literature review on articles published between January 2015 and January 2022 was conducted using the MEDLINE and ScienceDirect databases, following the PRISMA methodology, using the keywords "dosimetric comparison" and "brain metastases". The included articles compared two or more SRT techniques for treating single BM and considered at least two parameters among: conformity (CI), homogeneity (HI) and gradient (GI) indexes, delivery treatment time, and dose-volume of normal brain tissue. Eleven studies were analyzed. The heterogeneous lesions along with the different definitions of dosimetric indexes rendered the studied comparison almost unattainable. Gamma Knife (GK) and volumetric modulated arc therapy (VMAT) provide better CI and GI and ensure the sparing of healthy tissue. To conclude, it is crucial to optimize dosimetric indexes to minimize radiation exposure to healthy tissue, particularly in cases of reirradiation. Consequently, there is a need for future well-designed studies to establish guidelines for selecting the appropriate SRT technique based on the treated BMs' characteristics.

Inclusion of Nitrofurantoin into the Realm of Cancer Chemotherapy via Biology-Oriented Synthesis and Drug Repurposing.

Structural modifications of the antibacterial drug nitrofurantoin were envisioned, employing drug repurposing and biology-oriented drug synthesis, to serve as possible anticancer agents. Eleven compounds showed superior safety in non-cancerous human cells. Their antitumor efficacy was assessed on colorectal, breast, cervical, and liver cancer cells. Three compounds induced oxidative DNA damage in cancer cells with subsequent cellular apoptosis. They also upregulated the expression of Bax while downregulated that of Bcl-2 along with activating caspase 3/7. The DNA damage induced by these compounds, demonstrated by pATM nuclear shuttling, was comparable in both MCF7 and MDA-MB-231 (p53 mutant) cell lines. Mechanistic studies confirmed the dependence of these compounds on p53-mediated pathways as they suppressed the p53-MDM2 interaction. Indeed, exposure of radiosensitive prostatic cancer cells to low non-cytotoxic concentrations of compound 1 enhanced the cytotoxic response to radiation indicating a possible synergistic effect. In vivo antitumor activity was verified in an MCF7-xenograft animal model.

Radiosensitizing Effect of Curcumin on Human Bladder Cancer Cell Lines: Impact on DNA Repair Mechanisms.

Chemo-radiotherapy is one of the promising approaches to treat bladder cancer, but its effectiveness is limited to sensitive patients. Polyphenol curcumin has shown anticancer and radiosensitizing potentials, but the mechanism is not fully understood. Here, the In Vitro response of UM-UC5 and UM-UC6 bladder cell lines to curcumin and radiation treatments was evaluated. The effect of curcumin on the DNA double-strand breaks repair system after treatment with ionizing radiation (2 Gy) was determined by immunofluorescence. Cell viability, proliferation, and survival were performed using trypan blue, MTT, clonogenic, and sphere-forming assays. The migratory ability of both cells was assessed by wound healing. We showed that curcumin treatment increased the radiosensitivity by modifying the DNA double-strand breaks repair kinetics of the most radioresistant cells UM-UC6 without affecting the radiosensitive UM-UC5. Moreover, UM-UC6 cell survival and proliferation was significantly decreased after the combination of curcumin with radiation. Bladder cell migration was also inhibited considerably. Curcumin was also shown to reduce the number and the volume of bladder cancer spheres of both cell lines. This study revealed that curcumin was able to radiosensitize resistant bladder cell line without affecting the sensitive one with minimal side effects through enhancing DNA damage signaling and repair pathway.

Central nervous system tumors and three-dimensional cell biology: Current and future perspectives in modeling.

Central nervous system (CNS) tumors are a variety of distinct neoplasms that present multiple challenges in terms of treatment and prognosis. Glioblastoma, the most common primary tumor in adults, is associated with poor survival and remains one of the least treatable neoplasms. These tumors are highly heterogenous and complex in their nature. Due to this complexity, traditional cell culturing techniques and methods do not provide an ideal recapitulating model for the study of these tumors' behavior in vivo. Two-dimensional models lack the spatial arrangement, the heterogeneity in cell types, and the microenvironment that play a large role in tumor cell behavior and response to treatment. Recently, scientists have turned towards three-dimensional culturing methods, namely spheroids and organoids, as they have been shown to recapitulate tumors in a more faithful manner to their in vivo counterparts. Moreover, tumor-on-a-chip systems have lately been employed in CNS tumor modeling and have shown great potential in both studying the pathophysiology and therapeutic testing. In this review, we will discuss the current available literature on in vitro three-dimensional culturing models in CNS tumors, in addition to presenting their advantages and current limitations. We will also elaborate on the future implications of these models and their benefit in the clinical setting.

Tideglusib attenuates growth of neuroblastoma cancer stem/progenitor cells in vitro and in vivo by specifically targeting GSK-3ß.

BACKGROUND: Neuroblastoma (NB) is the most frequently diagnosed extracranial solid tumor among the pediatric population. It is an embryonic tumor with high relapse rates pertaining to the presence of dormant slowly dividing cancer stem cells (CSC) within the tumor bulk that are responsible for therapy resistance. Therefore, there is a dire need to develop new therapeutic approaches that specifically target NB CSCs. Glycogen synthase kinase (GSK)-3ß is a serine/threonine kinase that represents a common signaling node at the intersection of many pathways implicated in NB CSCs. GSK-3ß sustains the survival and maintenance of CSCs and renders them insensitive to chemotherapeutic agents and radiation. METHODS: In our study, we aimed at evaluating the potential anti-tumor effect of Tideglusib (TDG), an irreversible GSK-3ß inhibitor drug, on three human NB cell lines, SK-N-SH, SH-SY5Y, and IMR-32. RESULTS: Our results showed that TDG significantly reduced cell proliferation, viability, and migration of the NB cells, in a dose- and time-dependent manner, and also significantly hindered the neurospheres formation eradicating the self-renewal ability of highly resistant CSCs. Besides, TDG potently reduced CD133 cancer stem cell marker expression in both SH-SY5Y cells and G1 spheres. Lastly, TDG inhibited NB tumor growth and progression in vivo. CONCLUSION: Collectively, we concluded that TDG could serve as an effective treatment capable of targeting the NB CSCs and hence overcoming therapy resistance. Yet, future studies are warranted to further investigate its potential role in NB and decipher the subcellular and molecular mechanisms underlying this role.

The potential use of tideglusib as an adjuvant radio-therapeutic treatment for glioblastoma multiforme cancer stem-like cells.

BACKGROUND: Glioblastoma multiforme (GBM), a stage IV astrocytoma, is the most common brain malignancy among adults. Conventional treatments of surgical resection followed by radio and/or chemotherapy fail to completely eradicate the tumor. Resistance to the currently available therapies is mainly attributed to a subpopulation of cancer stem cells (CSCs) present within the tumor bulk that self-renew leading to tumor relapse with time. Therefore, identification of characteristic markers specific to these cells is crucial for the development of targeted therapies. Glycogen synthase kinase 3 (GSK-3), a serine-threonine kinase, is deregulated in a wide range of diseases, including cancer. In GBM, GSK-3ß is overexpressed and its suppression in vitro has been shown to induce apoptosis of cancer cells. METHODS: In our study, we assessed the effect of GSK-3ß inhibition with Tideglusib (TDG), an irreversible non-ATP competitive inhibitor, using two human GBM cell lines, U-251 MG and U-118 MG. In addition, we combined TDG with radiotherapy to assess whether this inhibition enhances the effect of standard treatment. RESULTS: Our results showed that TDG significantly reduced cell proliferation, cell viability, and migration of both GBM cell lines in a dose- and time-dependent manner in vitro. Treatment with TDG alone and in combination with radiation significantly decreased the colony formation of U-251 MG cells and the sphere formation of both cell lines, by targeting and reducing their glioblastoma cancer stem-like cells (GSCs) population. Finally, cells treated with TDG showed an increased level of unrepaired radio-induced DNA damage and, thus, became sensitized toward radiation. CONCLUSIONS: In conclusion, TDG has proven its effectiveness in targeting the cancerous properties of GBM in vitro and may, hence, serve as a potential adjuvant radio-therapeutic agent to better target this deadly tumor.

Drug repurposing towards targeting cancer stem cells in pediatric brain tumors.

In the pediatric population, brain tumors represent the most commonly diagnosed solid neoplasms and the leading cause of cancer-related deaths globally. They include low-grade gliomas (LGGs), medulloblastomas (MBs), and other embryonal, ependymal, and neuroectodermal tumors. The mainstay of treatment for most brain tumors includes surgical intervention, radiation therapy, and chemotherapy. However, resistance to conventional therapy is widespread, which contributes to the high mortality rates reported and lack of improvement in patient survival despite advancement in therapeutic research. This has been attributed to the presence of a subpopulation of cells, known as cancer stem cells (CSCs), which reside within the tumor bulk and maintain self-renewal and recurrence potential of the tumor. An emerging promising approach that enables identifying novel therapeutic strategies to target CSCs and overcome therapy resistance is drug repurposing or repositioning. This is based on using previously approved drugs with known pharmacokinetic and pharmacodynamic characteristics for indications other than their traditional ones, like cancer. In this review, we provide a synopsis of the drug repurposing methodologies that have been used in pediatric brain tumors, and we argue how this selective compilation of approaches, with a focus on CSC targeting, could elevate drug repurposing to the next level.

Assessing Radiosensitivity of Bladder Cancer in vitro: A 2D vs. 3D Approach.

Background: Bladder cancer is the fourth most commonly diagnosed cancer among males worldwide. Current treatment strategies established for bladder cancer mainly consist of cystectomy yet advances in radiation therapy have pointed to the value of organ-preserving strategies in preserving patients' quality of life. Aim: To study and compare the radiosensitivity in two-dimension (2D) and physiologically-relevant three-dimension (3D) in vitro culture of three human bladder cancer cell lines, RT4, T24, and UM-UC-3. Materials and Methods: Clonogenic assay was performed to assess cells' radiosensitivity in 2D. Employing the 3D Matrigel™-based cultures to enrich for cancer stem cells (CSCs) allowed us to assess the survival of this subpopulation of cells via evaluating the number, i.e., sphere forming unit (SFU), and the sizes of cultured spheres, formed from cells exposed to different radiation doses compared to non-irradiated cells. Results: Irradiating cells with increasing radiation doses revealed highest survival rates with RT4 cells in 2D, followed by T24 and UM-UC-3. In 3D, however, UM-UC-3 cells were shown to be the most radio-resistant as evidenced by the number of spheres formed, yet they displayed the least efficient volume reduction/regression (VR), whilst the volume decreased significantly for both RT4 and T24 cells. Sphere VR and sphere ratio (SR) values were then plotted against each other demonstrating a linear correlation between volume and number with RT4 and UM-UC-3 cell lines, but not T24. Lastly, multiple regression model was employed to evaluate the possibility of obtaining a function combining both 3D parameters, SR and VR, with the surviving fraction (SF) in 2D, and showed a linear regression for T24 cells only, with a correlation coefficient of 0.97 for the combined parameters. Conclusion: We were able to radiobiologically characterize 3 human bladder cancer cell lines showing differential effects of radiation between 2D and 3D culture systems, paving the way for achieving better assessment of radiosensitivity of bladder cancer in vitro.