Late gastrointestinal tissue effects after hypofractionated radiation therapy of the pancreas

Background To consolidate literature reports of serious late gastrointestinal toxicities after hypofractionated radiation treatment of pancreatic cancer and attempt to derive normal tissue complication probability (NTCP) parameters using the Lyman-Kutcher-Burman model. Methods Published reports of late grade 3 or greater gastrointestinal toxicity after hypofractionated treatment of pancreatic cancer were reviewed. The biologically equivalent dose in 1.8 Gy fractions was calculated using the EQD model. NTCP parameters were calculated using the LKB model assuming 1–5 % of the normal tissue volume was exposed to the prescription dose with α/β ratios of 3 or 4. Results A total of 16 human studies were examined encompassing a total of 1160 patients. Toxicities consisted of ulcers, hemorrhages, obstructions, strictures, and perforations. Non-hemorrhagic and non-perforated ulcers occurred at a rate of 9.1 % and were the most commonly reported toxicity. Derived NTCP parameter ranges were as follows: n = 0.38–0.63, m = 0.48–0.49, and TD50 = 35–95 Gy. Regression analysis showed that among various study characteristics, dose was the only significant predictor of toxicity. Conclusions Published gastrointestinal toxicity reports after hypofractionated radiotherapy for pancreatic cancer were compiled. Median dose was predictive of late grade ≥ 3 gastrointestinal toxicity. Preliminary NTCP parameters were derived for multiple volume constraints

High-throughput 2-hydroxyglutarate Assays for Biological Screening in IDH Mutant Cells

Cancer cells display altered metabolic profiles that can be exploited with targeted therapeutics. The amino acid glutamine is shunted toward anabolic reactions and contributes to the production of 2-hydroxyglutarate (2HG), an onco-metabolite aberrantly elevated in several cancers. 2HG is structurally similar to α-ketoglutarate (αKG) and can modulate the activity of several αKG dependent enzymes including histone and DNA demethylases, as a well as prolyl hydroxylases. Modulation of these enzymes leads to transformation and blocked differentiation. Thus, inhibition of 2HG production could be therapeutic in patients with IDH mutant malignancies. A facile and high-throughput method for quantification of 2HG is needed to allow for large scale compound and siRNA screens to identify new strategies for reducing 2HG levels. Herein, we developed novel fluorimetric microplate assay for quantitation of 2HG and performed an unbiased small molecule screen in live cells to identify compounds capable of perturbing 2HG production. Zaprinast, a known PDE5 inhibitor, was identified as a modulator of 2HG production and confirmed to lower 2HG levels in vivo. The mechanism of action was not due to cGMP stabilization, but rather, profiling of metabolites upstream of mutant IDH1 pointed to targeted inhibition of the enzyme glutaminase (GLS1). With purified GLS1 in vitro, Zaprinast showed xi classic noncompetitive inhibition kinetics (Ki = 220 M). In human astrocytes expressing mutant IDH1, Zaprinast-mediated inhibition of GLS1reversed histone hypermethylation and cell growth in soft agar. Additionally, treatment of glutamine-addicted pancreatic ductal adenocarcinoma cells with Zaprinast reduced growth, increased ROS levels, and sensitized cells to oxidative damage, mimicking the effects of glutamine deprivation; metabolic rescue with glutamate reversed the Zaprinast-mediated blockade of GLS1. Thus, Zaprinast possesses efficacious off-target effects against glutamine metabolism, providing a convenient tool compound for further investigation of the linkages between GLS1 and 2HG-mediated oncogenesis as well as therapeutic development against IDH mutant or glutamine-addicted cancers

Late gastrointestinal tissue effects after hypofractionated radiation therapy of the pancreas

Background: To consolidate literature reports of serious late gastrointestinal toxicities after hypofractionatedradiation treatment of pancreatic cancer and attempt to derive normal tissue complication probability (NTCP)parameters using the Lyman-Kutcher-Burman model.Methods: Published reports of late grade 3 or greater gastrointestinal toxicity after hypofractionated treatment ofpancreatic cancer were reviewed. The biologically equivalent dose in 1.8 Gy fractions was calculated using the EQDmodel. NTCP parameters were calculated using the LKB model assuming 1--5 % of the normal tissue volume wasexposed to the prescription dose with a/β ratios of 3 or 4.Results: A total of 16 human studies were examined encompassing a total of 1160 patients. Toxicities consisted ofulcers, hemorrhages, obstructions, strictures, and perforations. Non-hemorrhagic and non-perforated ulcers occurredat a rate of 9.1 % and were the most commonly reported toxicity. Derived NTCP parameter ranges were as follows:n = 0.38--0.63, m = 0.48--0.49, and TD50 = 35--95 Gy. Regression analysis showed that among various studycharacteristics, dose was the only significant predictor of toxicity.Conclusions: Published gastrointestinal toxicity reports after hypofractionated radiotherapy for pancreatic cancerwere compiled. Median dose was predictive of late grade ≥ 3 gastrointestinal toxicity. Preliminary NTCP parameterswere derived for multiple volume constraints

Whole-genome analysis informs breast cancer response to aromatase inhibition

To correlate the variable clinical features of estrogen receptor positive (ER+) breast cancer with somatic alterations, we studied pre-treatment tumour biopsies accrued from patients in a study of neoadjuvant aromatase inhibitor (AI) therapy by massively parallel sequencing and analysis. Eighteen significantly mutated genes were identified, including five genes (RUNX1, CBFB, MYH9, MLL3 and SF3B1) previously linked to hematopoietic disorders. Mutant MAP3K1 was associated with Luminal A status, low grade histology and low proliferation rates whereas mutant TP53 associated with the opposite pattern. Moreover, mutant GATA3 correlated with suppression of proliferation upon AI treatment. Pathway analysis demonstrated mutations in MAP2K4, a MAP3K1 substrate, produced similar perturbations as MAP3K1 loss. Distinct phenotypes in ER+ breast cancer are associated with specific patterns of somatic mutations that map into cellular pathways linked to tumor biology but most recurrent mutations are relatively infrequent. Prospective clinical trials based on these findings will require comprehensive genome sequencing