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Radiation therapy is commonly used to treat glioblastoma multiforme (GBM) brain tumors. Ionizing radiation (IR) induces dose-specific variations in transcriptional programs, implicating that they are tightly regulated and critical components in the tumor response and survival. Yet, our understanding of the downstream molecular events triggered by effective vs. non-effective IR doses is limited. Herein, we report that variations in the genetic programs are positively and functionally correlated with the exposure to effective or non-effective IR doses. Genome architecture analysis revealed that gene regulation is spatially and temporally coordinated with DNA repair kinetics. The radiation-activated genes were pre-positioned in active sub-nuclear compartments and were upregulated following the DNA damage response, while the DNA repair activity shifted to the inactive heterochromatic spatial compartments. The IR dose affected the levels of DNA damage repair and transcription modulation, but not the order of the events, which was linked to their spatial nuclear positioning. Thus, the distinct coordinated temporal dynamics of DNA damage repair and transcription reprogramming in the active and inactive sub-nuclear compartments highlight the importance of high-order genome organization in synchronizing the molecular events following IR. [ABSTRACT FROM AUTHOR]

Simple Summary: CX3CR1 is present in a subset of the immune cells in the tumor microenvironment; however, their function after radiation therapy remains unknown. We found that radiation induces a significant influx of CX3CR1-expressing immune cells, notably macrophages, into the tumor microenvironment. Co-culturing irradiated lung carcinoma cells with CX3CR1-deficient macrophages reduced proliferation and increased apoptosis of the cancer cells. Interestingly, deficiency of CX3CR1 in macrophages led to the redistribution of the irradiated cancer cells in the S-phase, parallel to increased expression of cyclin E1, required for cell cycle G1/S transition. In addition, deficiency in CX3CR1 in macrophages altered cytokine secretion with decreased interleukin 6, a mediator of cancer cell survival and proliferation. Lastly, we show that in vivo ablation of CX3CR1-expressing cells attenuates tumor progression following radiation and sensitizes the tumor to S-phase-specific chemotherapy. Introduction: Chemokine (C-X3-C Motif) Receptor 1 (CX3CR1) is present in a subset of the immune cells in the tumor microenvironment (TME) and plays an essential and diverse role in cancer progression. However, its potential function in the irradiated TME remains unknown. Materials and Methods: A mouse lung cancer model was performed by subcutaneously inoculating Lewis Lung Carcinoma (LLC) cells expressing luciferase (Luc-2) and mCherry cells in CX3CR1GFP/GFP, CX3CR1DTR/+, and wild–type (WT) mice. Bioluminescence imaging, clonogenic assay, and flow cytometry were used to assess tumor progression, proliferation, and cell composition after radiation. Results: Radiation provoked a significant influx of CX3CR1-expressing immune cells, notably monocytes and macrophages, into the TME. Co-culturing irradiated LLC cells with CX3CR1-deficient monocytes, and macrophages resulted in reduced clonogenic survival and increased apoptosis of the cancer cells. Interestingly, deficiency of CX3CR1 in macrophages led to a redistribution of the irradiated LLC cells in the S-phase, parallel to increased expression of cyclin E1, required for cell cycle G1/S transition. In addition, the deficiency of CX3CR1 expression in macrophages altered the cytokine secretion with a decrease in interleukin 6, a crucial mediator of cancer cell survival and proliferation. Next, LLC cells were injected subcutaneously into CX3CR1DTR/+ mice, sensitive to diphtheria toxin (DT), and WT mice. After injection, tumors were irradiated with 8 Gy, and mice were treated with DT, leading to conditional ablation of CX3CR1-expressing cells. After three weeks, CX3CR1-depleted mice displayed reduced tumor progression. Furthermore, combining the S-phase-specific chemotherapeutic gemcitabine with CX3CR1 cell ablation resulted in additional attenuation of tumor progression. Conclusions: CX3CR1-expressing mononuclear cells invade the TME after radiation therapy in a mouse lung cancer model. CX3CR1 cell depletion attenuates tumor progression following radiation and sensitizes the tumor to S–phase-specific chemotherapy. Thus, we propose a novel strategy to improve radiation sensitivity by targeting the CX3CR1-expressing immune cells. [ABSTRACT FROM AUTHOR]

Background: Animal brain-tumor models have demonstrated a synergistic interaction between radiation therapy and a ketogenic diet (KD). Metformin has in-vitro anti-cancer activity, through AMPK activation and mTOR inhibition. We hypothesized that the metabolic stress induced by a KD combined with metformin would enhance radiation's efficacy. We sought to assess the tolerability and feasibility of this approach. Methods: A single-institution phase I clinical trial. Radiotherapy was either 60 or 35 Gy over 6 or 2 weeks, for newly diagnosed and recurrent gliomas, respectively. The dietary intervention consisted of a Modified Atkins Diet (ModAD) supplemented with medium chain triglycerides (MCT). There were three cohorts: Dietary intervention alone, and dietary intervention combined with low-dose or high-dose metformin; all patients received radiotherapy. Factors associated with blood ketone levels were investigated using a mixed-model analysis. Results: A total of 13 patients were accrued, median age 61 years, of whom six had newly diagnosed and seven with recurrent disease. All completed radiation therapy; five patients stopped the metabolic intervention early. Metformin 850 mg three-times daily was poorly tolerated. There were no serious adverse events. Ketone levels were associated with dietary factors (ketogenic ratio, p < 0.001), use of metformin (p = 0. 02) and low insulin levels (p = 0.002). Median progression free survival was ten and four months for newly diagnosed and recurrent disease, respectively. Conclusions: The intervention was well tolerated. Higher serum ketone levels were associated with both dietary intake and metformin use. The recommended phase II dose is eight weeks of a ModAD combined with 850 mg metformin twice daily. [ABSTRACT FROM AUTHOR]

Alternative splicing regulators have emerged as new players in cancer development, modulating the activities of many tumor suppressors and oncogenes and regulating the signaling pathways. However, little is known about the mechanisms by which these oncogenic splicing factors lead to cellular transformation. We have shown previously that the splicing factor serine and arginine splicing factor 1 (SRSF1; SF2/ASF) is a proto-oncogene, which is amplified in breast cancer and transforms immortal cells when overexpressed. In this study, we performed a structure–function analysis of SRSF1 and found that the RNA recognition motif 1 (RRM1) domain is required for its oncogenic activity. Deletion of RRM1 eliminated the splicing activity of SRSF1 on some of its endogenous targets. Moreover, we found that SRSF1 elevates the expression of B-Raf and activates the mitogen-activated protein kinase kinase (MEK) extracellular signal-regulated kinase (ERK) pathway and that RRM1 is required for this activation as well. B-Raf-MEK-ERK activation by SRSF1 contributes to transformation as pharmacological inhibition of MEK1 inhibits SRSF1-mediated transformation. In conclusion, RRM1 of SRSF1 is both required (and when tethered to the RS domain) also sufficient to activate the Raf-MEK-ERK pathway and to promote cellular transformation. [ABSTRACT FROM PUBLISHER]