Incompatibilities Involving Yeast Mismatch Repair Genes: A Role for Genetic Modifiers and Implications for Disease Penetrance and Variation in Genomic Mutation Rates

Genetic background effects underlie the penetrance of most genetically determined phenotypes, including human diseases. To explore how such effects can modify a mutant phenotype in a genetically tractable system, we examined an incompatibility involving the MLH1 and PMS1 mismatch repair genes using a large population sample of geographically and ecologically diverse Saccharomyces cerevisiae strains. The mismatch repair incompatibility segregates into naturally occurring yeast strains, with no strain bearing the deleterious combination. In assays measuring the mutator phenotype conferred by different combinations of MLH1 and PMS1 from these strains, we observed a mutator phenotype only in combinations predicted to be incompatible. Surprisingly, intragenic modifiers could be mapped that specifically altered the strength of the incompatibility over a 20-fold range. Together, these observations provide a powerful model in which to understand the basis of disease penetrance and how such genetic variation, created through mating, could result in new mutations that could be the raw material of adaptive evolution in yeast populations

Real-time prostate motion assessment: image-guidance and the temporal dependence of intra-fraction motion

BACKGROUND: The rapid adoption of image-guidance in prostate intensity-modulated radiotherapy (IMRT) results in longer treatment times, which may result in larger intrafraction motion, thereby negating the advantage of image-guidance. This study aims to qualify and quantify the contribution of image-guidance to the temporal dependence of intrafraction motion during prostate IMRT. METHODS: One-hundred and forty-three patients who underwent conventional IMRT (n=67) or intensity-modulated arc therapy (IMAT/RapidArc, n=76) for localized prostate cancer were evaluated. Intrafraction motion assessment was based on continuous RL (lateral), SI (longitudinal), and AP (vertical) positional detection of electromagnetic transponders at 10 Hz. Daily motion amplitudes were reported as session mean, median, and root-mean-square (RMS) displacements. Temporal effect was evaluated by categorizing treatment sessions into 4 different classes: IMRT(c) (transponder only localization), IMRT(cc) (transponder + CBCT localization), IMAT(c) (transponder only localization), or IMAT(cc) (transponder + CBCT localization). RESULTS: Mean/median session times were 4.15/3.99 min (IMAT(c)), 12.74/12.19 min (IMAT(cc)), 5.99/5.77 min (IMRT(c)), and 12.98/12.39 min (IMRT(cc)), with significant pair-wise difference (p<0.0001) between all category combinations except for IMRT(cc) vs. IMAT(cc) (p>0.05). Median intrafraction motion difference between CBCT and non-CBCT categories strongly correlated with time for RMS (t-value=17.29; p<0.0001), SI (t-value=−4.25; p<0.0001), and AP (t-value=2.76; p<0.0066), with a weak correlation for RL (t-value=1.67; p=0.0971). Treatment time reduction with non-CBCT treatment categories showed reductions in the observed intrafraction motion: systematic error (Σ)<0.6 mm and random error (σ)<1.2 mm compared with ≤0.8 mm and <1.6 mm, respectively, for CBCT-involved treatment categories. CONCLUSIONS: For treatment durations >4-6 minutes, and without any intrafraction motion mitigation protocol in place, patient repositioning is recommended, with at least the acquisition of the lateral component of an orthogonal image pair in the absence of volumetric imaging

Phase III, randomized trial of mirvetuximab soravtansine versus chemotherapy in patients with platinum-resistant ovarian cancer: primary analysis of FORWARD I.

Background Mirvetuximab soravtansine (MIRV) is an antibody-drug conjugate comprising a folate receptor alpha (FRα)-binding antibody, cleavable linker, and the maytansinoid DM4, a potent tubulin-targeting agent. The randomized, open-label, phase III study FORWARD I compared MIRV and investigator's choice chemotherapy in patients with platinum-resistant epithelial ovarian cancer (EOC).Patients and methods Eligible patients with 1-3 prior lines of therapy and whose tumors were positive for FRα expression were randomly assigned, in a 2 : 1 ratio, to receive MIRV (6 mg/kg, adjusted ideal body weight) or chemotherapy (paclitaxel, pegylated liposomal doxorubicin, or topotecan). The primary endpoint was progression-free survival [PFS, Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1, blinded independent central review] in the intention-to-treat (ITT) population and in the prespecified FRα high population.Results A total of 366 patients were randomized; 243 received MIRV and 109 received chemotherapy. The primary endpoint, PFS, did not reach statistical significance in either the ITT [hazard ratio (HR), 0.98, P = 0.897] or the FRα high population (HR, 0.69, P = 0.049). Superior outcomes for MIRV over chemotherapy were observed in all secondary endpoints in the FRα high population including improved objective response rate (24% versus 10%), CA-125 responses (53% versus 25%), and patient-reported outcomes (27% versus 13%). Fewer treatment-related grade 3 or higher adverse events (25.1% versus 44.0%), and fewer events leading to dose reduction (19.8% versus 30.3%) and treatment discontinuation (4.5% versus 8.3%) were seen with MIRV compared with chemotherapy.Conclusions In patients with platinum-resistant EOC, MIRV did not result in a significant improvement in PFS compared with chemotherapy. Secondary endpoints consistently favored MIRV, particularly in patients with high FRα expression. MIRV showed a differentiated and more manageable safety profile than chemotherapy

Uncertainties encountered in implementation of adaptive planning with in vivo dosimeters

Under a previously approved institutional review board protocol for prostate cancer patients, implanted metal-oxide semiconductor field-effect transistor dosimeters (dose verification system, Sicel Technologies) were used for measurement of the in vivo delivered daily dose. This dosimetric information provided the ability to adapt the plan if the measured doses did not match the dose expected from the planning system. Due to the inherent uncertainty in the dosimeters, the decision to adapt the treatment plan was made only if readings differed by more than 7 % for three consecutive days. To validate this method, we acquired daily cone beam computed tomography images for five patients, and the dose delivered to the dosimeters was calculated by use of (1) an automated procedure (MIM Maestro, MIM Software) and (2) the treatment planning system (XIO, Elekta). 72 % of the doses calculated automatically fell within 1 % of the doses calculated in the planning system, and 99 % agreed within 2 %. When compared to the calculated dose, 53 % of the in vivo measurements fell within 3 % of the calculated dose, 80 % fell within 5 %, and 9.8 % were greater than 7 %, but never on three consecutive days. The measured doses agreed reasonably well with the calculated doses, supporting the decision to adapt the plan only if there were discrepancies of more than 7 % over three consecutive days. Even with the inherent uncertainty in the dosimeters, this adaptive planning method can detect delivery inaccuracies that would not otherwise be caught with the use of only daily image guidance or other dose calculation surrogates

Identification of hemostatic genes expressed in human and rat leg muscles and a novel gene (LPP1/PAP2A) suppressed during prolonged physical inactivity (sitting)

<p>Abstract</p> <p>Background</p> <p>Partly because of functional genomics, there has been a major paradigm shift from solely thinking of skeletal muscle as contractile machinery to an understanding that it can have roles in paracrine and endocrine functions. Physical inactivity is an established risk factor for some blood clotting disorders. The effects of inactivity during sitting are most alarming when a person develops the enigmatic condition in the legs called deep venous thrombosis (DVT) or “coach syndrome,” caused in part by muscular inactivity. The goal of this study was to determine if skeletal muscle expresses genes with roles in hemostasis and if their expression level was responsive to muscular inactivity such as occurs in prolonged sitting.</p> <p>Methods</p> <p>Microarray analyses were performed on skeletal muscle samples from rats and humans to identify genes associated with hemostatic function that were significantly expressed above background based on multiple probe sets with perfect and mismatch sequences. Furthermore, we determined if any of these genes were responsive to models of physical inactivity. Multiple criteria were used to determine differential expression including significant expression above background, fold change, and non-parametric statistical tests.</p> <p>Results</p> <p>These studies demonstrate skeletal muscle tissue expresses at least 17 genes involved in hemostasis. These include the fibrinolytic factors tetranectin, annexin A2, and tPA; the anti-coagulant factors TFPI, protein C receptor, PAF acetylhydrolase; coagulation factors, and genes necessary for the posttranslational modification of these coagulation factors such as vitamin K epoxide reductase. Of special interest, lipid phosphate phosphatase-1 (LPP1/PAP2A), a key gene for degrading prothrombotic and proinflammatory lysophospholipids, was suppressed locally in muscle tissue within hours after sitting in humans; this was also observed after acute and chronic physical inactivity conditions in rats, and exercise was relatively ineffective at counteracting this effect in both species.</p> <p>Conclusions</p> <p>These findings suggest that skeletal muscle may play an important role in hemostasis and that muscular inactivity may contribute to hemostatic disorders not only because of the slowing of blood flow per se, but also potentially because of the contribution from genes expressed locally in muscles, such as LPP1.</p