Safety of pelvic and abdominal radiation therapy for patients with inflammatory bowel disease: a dosimetric analysis of acute bowel toxicity.

OBJECTIVES: Inflammatory bowel disease (IBD) has been considered a relative contraindication to radiation therapy (RT) due to the potential greater risk of RT-induced toxicities. This study aims to assess acute toxicity outcomes in patients with IBD treated with abdominal/pelvic RT. METHODS: After institutional review board approval, patients with IBD who received RT to the abdomen/pelvis were identified from an institutional research repository and their electronic medical records were reviewed. The IBD cohort was matched 1:1 with controls according to all of the following: radiotherapy, gender, disease site, age, and year of RT. Acute toxicity was defined as toxicity occurring within 3 months of RT. Primary outcomes were assessed via univariable logistic regression models and predicted probability of acute toxicity and acute gastrointestinal (GI) toxicity were plotted for the most significant covariates. IBD and control control cohorts were compared on demographic and toxicity variables using chi-square/Fisher's exact tests and Kruskal-Wallis tests where appropriate. RESULTS: We identified 62 patients with median age of 64 years (interquartile range [IQR] 54-70) who received RT from 2006-2022. Patients were treated with intensity-modulated RT (38; 61.3%), 3-dimensional conformal RT (12; 19.4%), and stereotactic body RT/brachytherapy (12; 19.4%). After RT, 28 (45.2%) and 23 (37.1%) patients experienced grade ≥2 acute (any) and acute GI toxicity, respectively. Higher overall RT dose and RT dose to small bowel were found to be signicantly associated with increased risk of grade ≥2 acute toxicities (OR=1.041 per unit Gy, 95% CI 1.005-1.084, p=0.034 and OR=1.046, 95% CI 1.018-1.082, p=0.003, respectively). Between IBD and control cohorts, there were no significant differences in grade ≥2 acute (any) and acute GI toxicities (p=0.710 and p=0.704, respectively). CONCLUSION: In patients with IBD treated with abdominal/pelvic RT for malignancy, RT was effective and well-tolerated. RT treatment planning should carefully consider the location(s) of IBD inflammation and dose to bowel structures, in particular, dose to small bowel.

Glucose Deprivation Promotes Pseudohypoxia and Dedifferentiation in Lung Adenocarcinoma.

Increased utilization of glucose is a hallmark of cancer. Sodium-glucose transporter 2 (SGLT2) is a critical player in glucose uptake in early-stage and well-differentiated lung adenocarcinoma (LUAD). SGLT2 inhibitors, which are FDA approved for diabetes, heart failure, and kidney disease, have been shown to significantly delay LUAD development and prolong survival in murine models and in retrospective studies in diabetic patients, suggesting that they may be repurposed for lung cancer. Despite the antitumor effects of SGLT2 inhibition, tumors eventually escape treatment. Here, we studied the mechanisms of resistance to glucose metabolism-targeting treatments. Glucose restriction in LUAD and other tumors induced cancer cell dedifferentiation, leading to a more aggressive phenotype. Glucose deprivation caused a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. The dedifferentiated phenotype depended on unbalanced EZH2 activity that suppressed prolyl-hydroxylase PHD3 and increased expression of hypoxia-inducible factor 1α (HIF1α), triggering epithelial-to-mesenchymal transition. Finally, a HIF1α-dependent transcriptional signature of genes upregulated by low glucose correlated with prognosis in human LUAD. Overall, this study furthers current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying targets to prevent the development of resistance to therapies targeting glucose metabolism. SIGNIFICANCE: Epigenetic adaptation allows cancer cells to overcome the tumor-suppressive effects of glucose restriction by inducing dedifferentiation and an aggressive phenotype, which could help design better metabolic treatments.

Glucose deprivation promotes pseudo-hypoxia and de-differentiation in lung adenocarcinoma.

Increased utilization of glucose is a hallmark of cancer. Several studies are investigating the efficacy of glucose restriction by glucose transporter blockade or glycolysis inhibition. However, the adaptations of cancer cells to glucose restriction are unknown. Here, we report the discovery that glucose restriction in lung adenocarcinoma (LUAD) induces cancer cell de-differentiation, leading to a more aggressive phenotype. Glucose deprivation causes a reduction in alpha-ketoglutarate (αKG), leading to attenuated activity of αKG-dependent histone demethylases and histone hypermethylation. We further show that this de-differentiated phenotype depends on unbalanced EZH2 activity, causing inhibition of prolyl-hydroxylase PHD3 and increased expression of hypoxia inducible factor 1α (HIF1α), triggering epithelial to mesenchymal transition. Finally, we identified an HIF1α-dependent transcriptional signature with prognostic significance in human LUAD. Our studies further current knowledge of the relationship between glucose metabolism and cell differentiation in cancer, characterizing the epigenetic adaptation of cancer cells to glucose deprivation and identifying novel targets to prevent the development of resistance to therapies targeting glucose metabolism.