Increasing evidence demonstrates that radiation acts as an immune stimulus, recruiting immune mediators that enable anti-tumor responses within and outside the radiation field. There has been a rapid expansion in the number of clinical trials harnessing radiation to enhance antitumor immunity. If positive, results of these trials will lead to a paradigm shift in the use of radiotherapy. In this review, we discuss the rationale for trials combining radiation with various immunotherapies, provide an update of recent clinical trial results and highlight trials currently in progress. We also address issues pertaining to the optimal incorporation of immunotherapy with radiation, including sequencing of treatment, radiation dosing and evaluation of clinical trial endpoints.

BackgroundNew tools are needed to predict outcomes of ovarian cancer patients treated with platinum-based chemotherapy. We hypothesized that a molecular score based on expression of genes that are involved in platinum-induced DNA damage repair could provide such prognostic information.MethodsGene expression data was extracted from The Cancer Genome Atlas (TCGA) database for 151 DNA repair genes from tumors of serous ovarian cystadenocarcinoma patients (n = 511). A molecular score was generated based on the expression of 23 genes involved in platinum-induced DNA damage repair pathways. Patients were divided into low (scores 0–10) and high (scores 11–20) score groups, and overall survival (OS) was analyzed by Kaplan–Meier method. Results were validated in two gene expression microarray datasets. Association of the score with OS was compared with known clinical factors (age, stage, grade, and extent of surgical debulking) using univariate and multivariable Cox proportional hazards models. Score performance was evaluated by receiver operating characteristic (ROC) curve analysis. Correlations between the score and likelihood of complete response, recurrence-free survival, and progression-free survival were assessed. Statistical tests were two-sided.ResultsImproved survival was associated with being in the high-scoring group (high vs low scores: 5-year OS, 40% vs 17%, P < .001), and results were reproduced in the validation datasets (P < .05). The score was the only pretreatment factor that showed a statistically significant association with OS (high vs low scores, hazard ratio of death = 0.40, 95% confidence interval = 0.32 to 0.66, P < .001). ROC curves indicated that the score outperformed the known clinical factors (score in a validation dataset vs clinical factors, area under the curve = 0.65 vs 0.52). The score positively correlated with complete response rate, recurrence-free survival, and progression-free survival (Pearson correlation coefficient [r2] = 0.60, 0.84, and 0.80, respectively; P < .001 for all).ConclusionThe DNA repair pathway–focused score can be used to predict outcomes and response to platinum therapy in ovarian cancer patients.

BackgroundStereotactic Body Radiotherapy (SBRT) has excellent control rates for low- and intermediate-risk prostate carcinoma.The role of SBRT for high-risk disease remains less studied. We present long-term results on a cohort of patients with NCCN-defined high-risk disease treated with SBRT.MethodsWe retrospectively studied 97 patients treated as part of prospective trial from 2006–2010 with SBRT alone (n = 52) to dose of 35–36.25 Gy in 5 fractions, or pelvic radiation to 45 Gy followed by SBRT boost of 19–21 Gy in 3 fractions (n = 45). 46 patients received Androgen Deprivation Therapy. Quality of life and bladder/bowel toxicity was assessed using the Expanded Prostate Index Composite (EPIC) and RTOG toxicity scale.ResultsMedian followup was 60 months. 6-year biochemical disease-free survival (bDFS) was 69%. On multivariate analysis, only PSA remained significant (P < 0.01) for bDFS. Overall toxicity was mild, with 5% Grade 2–3 urinary and 7% Grade 2 bowel toxicity. Use of pelvic radiotherapy was associated with significantly higher bowel toxicity (P = .001). EPIC scores declined for the first six months and then returned towards baseline.ConclusionsSBRT appears to be a safe and effective treatment for high-risk prostate carcinoma. Our data suggests that SBRT alone may be the optimal approach. Further followup and additional studies is required to corroborate our results.

Prokaryotic genomes are substantially diverse, even when from closely related species, with the resulting phenotypic diversity representing a repertoire of adaptations to specific constraints. Within the microbial population, genome content may not be fixed, as changing selective forces favor particular phenotypes; however, organisms well adapted to particular niches may have evolved mechanisms to facilitate such plasticity. The highly diverse Helicobacter pylori is a model for studying genome plasticity in the colonization of individual hosts. For H. pylori, neither point mutation, nor intergenic recombination requiring the presence of multiple colonizing strains, is sufficient to fully explain the observed diversity. Here we demonstrate that H. pylori has extensive, nonrandomly distributed repetitive chromosomal sequences, and that recombination between identical repeats contributes to the variation within individual hosts. That H. pylori is representative of prokaryotes, especially those with smaller (<2 megabases) genomes, that have similarly extensive direct repeats, suggests that recombination between such direct DNA repeats is a widely conserved mechanism to promote genome diversification. P rokaryotes that successfully colonize niches for extended periods of time must be capable of adapting to changing environmental stresses (1). Genomic diversity, caused by spontaneous point mutation, intragenomic rearrangement, and horizontal gene acquisition (2), creates a phenotypically diverse population from which the most-fit variants are selected. Colonization of the primate stomach by Helicobacter pylori is prolonged, usually persisting for decades without host clearance (3). That essentially all H. pylori isolates obtained from unrelated individuals are genetically distinguishable (4), and that diverse subclones have been identified in individual hosts (5-7) suggest that persistence may be facilitated by the organism's ability to adapt to dynamic environments by continuous change (8). HIV and other pathogenic viruses that persistently infect hosts employ similar strategies of ''quasispecies'' development to increase fitness success (9).For H. pylori, neither spontaneous point mutation (10) nor recombination with other bacterial cells (11) is sufficient to explain observed intrahost genetic variation (5, 7). Computational analysis of the fully sequenced H. pylori strain 26695 (12) indicates numerous direct DNA repeats (13, 14); however, these studies do not demonstrate a role for repeats through experimental analyses, provide evidence that these repeat structures are involved in any biologic function, or assess how the nonrandom distribution of repeats may affect the physiology or evolution of the host organism. Because recombination involving direct repeats allows for deletion or duplication of intervening sequences (15), we sought to determine the extent to which H. pylori uses repetitive DNA sequences to generate diversity. Our observations provide evidence that the presence of extensive, nonrandomly distribu...

Microorganisms that persist in single hosts face particular challenges. Helicobacter pylori, an obligate bacterial parasite of the human stomach, has evolved a lifestyle that features interstrain competition and intraspecies cooperation, both of which involve horizontal gene transfer. Microbial species must maintain genomic integrity, yet H. pylori has evolved a complex nonlinear system for diversification that exists in dynamic tension with the mechanisms for ensuring fidelity. Here, we review these tensions and propose that they create a dynamic pool of genetic variants that is sufficiently genetically diverse to allow H. pylori to occupy all of the potential niches in the stomach.

MutS homologs, identified in nearly all bacteria and eukaryotes, include the bacterial proteins MutS1 and MutS2 and the eukaryotic MutS homologs 1 to 7, and they often are involved in recognition and repair of mismatched bases and small insertion/deletions, thereby limiting illegitimate recombination and spontaneous mutation. To explore the relationship of MutS2 to other MutS homologs, we examined conserved protein domains. Fundamental differences in structure between MutS2 and other MutS homologs suggest that MutS1 and MutS2 diverged early during evolution, with all eukaryotic homologs arising from a MutS1 ancestor. Data from MutS1 crystal structures, biochemical results from MutS2 analyses, and our phylogenetic studies suggest that MutS2 has functions distinct from other members of the MutS family. A mutS2 mutant was constructed in Helicobacter pylori, which lacks mutS1 and mismatch repair genes mutL and mutH. We show that MutS2 plays no role in mismatch or recombinational repair or deletion between direct DNA repeats. In contrast, MutS2 plays a significant role in limiting intergenomic recombination across a range of donor DNA tested. This phenotypic analysis is consistent with the phylogenetic and biochemical data suggesting that MutS1 and MutS2 have divergent functions.MutS homologs (MSH) have been identified in most prokaryotic and all eukaryotic organisms examined. Prokaryotes have two homologs (MutS1 and MutS2), whereas seven MSH proteins (MSH1 to MSH7) have been identified in eukaryotes (16,19,23). The homodimer MutS1 and heterodimers MSH2-MSH3 and MSH2-MSH6 are primarily involved in mitotic mismatch repair, whereas MSH4-MSH5 is involved in resolution of Holliday junctions during meiosis (1, 64). All members of the MutS family contain the highly conserved Walker A/B ATPase domain (16), and many share a common mechanism of action. MutS1, MSH2-MSH3, MSH2-MSH6, and MSH4-MSH5 dimerize to form sliding clamps, and recognition of specific DNA structures or lesions results in ADP/ATP exchange (27,45,49,64).The function of the second prokaryotic homolog, MutS2, is unknown. Sequence analyses reveal fundamental differences between MutS2 and other MutS family members (19). MutS2 proteins contain a conserved C-terminal domain of ϳ250 amino acid residues not found in other MutS homologs and lack the conserved N-terminal region present in most of the other MutS family members (43). According to one hypothesis, MutS2 is more closely related to the meiotic recombination proteins MSH4 and MSH5, while MutS1 is more closely related to MSH2,. This hypothesis suggests a gene duplication event early in the evolution of MutS, resulting in the two main MutS lineages, with MSH4 and MSH5 branching with MutS2 and MSH2, -3, and -6 branching with MutS1. Consistent with this hypothesis, MutS2 has been shown to not play a role in mismatch repair (13,59,69). However, arguing against this hypothesis is the lack of homology between MutS2 and MSH4-MSH5. According to another hypothesis, all eukaryotic MutS homologs evolved from one ancesto...

Objectives: Stereotactic body radiation therapy (SBRT) yields excellent disease control for low- and intermediate-risk prostate cancer by delivering high doses of radiation in a small number of fractions. Our report presents a 7-year update on treatment toxicity and quality of life (QOL) from 515 patients treated with prostate SBRT.Methods: From 2006 to 2009, 515 patients with clinically localized, low-, intermediate-, and high-risk prostate cancer were treated with SBRT using Cyberknife technology. Treatment consisted of 35–36.25 Gy in 5 fractions. Seventy-two patients received hormone therapy. Toxicity was assessed at each follow-up visit using the expanded prostate cancer index composite (EPIC) questionnaire and the radiation therapy oncology group urinary and rectal toxicity scale.Results: Median follow-up was 72 months. The actuarial 7-year freedom from biochemical failure was 95.8, 89.3, and 68.5% for low-, intermediate-, and high-risk groups, respectively (p < 0.001). No patients experienced acute Grade 3 or 4 acute complications. Fewer than 5% of patients had any acute Grade 2 urinary or rectal toxicity. Late toxicity was low, with Grade 2 rectal and urinary toxicity of 4 and 9.1%, respectively, and Grade 3 urinary toxicity of 1.7%. Mean EPIC urinary and bowel QOL declined at 1 month post-treatment, returned to baseline by 2 years and remained stable thereafter. EPIC sexual QOL declined by 23% at 6–12 months and remained stable afterwards. Of patients potent at baseline evaluation, 67% remained potent at last follow-up.Conclusion: This study suggests that SBRT, when administered to doses of 35–36.25 Gy, is efficacious and safe. With long-term follow-up in our large patient cohort, we continue to find low rates of late toxicity and excellent rates of biochemical control.

Objectives: Stereotactic body radiation therapy (SBRT) takes advantage of the prostate’s low α/β ratio to deliver a large radiation dose in few fractions. Initial studies on small groups of low-risk patients support SBRT’s potential for clinical efficacy while limiting treatment-related morbidity and maintained quality of life. This prospective study expands upon prior studies to further evaluate SBRT efficacy for a large patient population with organ confined, low- and intermediate-risk prostate cancer patients.Methods: Four hundred seventy-seven patients with prostate cancer received CyberKnife SBRT. The median age was 68.6 years and the median PSA was 5.3 ng/mL. Three hundred twenty-four patients were low-risk (PSA <10 ng/mL and Gleason <7), 153 were intermediate-risk (PSA 10–20 ng/mL or Gleason = 7). Androgen deprivation therapy was administered to 51 patients for up to 6 months. One hundred fifty-four patients received 35 Gy delivered in five daily fractions; the remaining patients received a total dose of 36.25 Gy in five daily fractions. Biochemical failure was assessed using the phoenix criterion.Results: Median follow-up was 72 months. The median PSA at 7 years was 0.11 ng/mL. Biochemical failures occurred for 11 low-risk patients (2 locally), 14 intermediate-risk patients (3 locally). The actuarial 7-year freedom from biochemical failure was 95.6 and 89.6% for low- and intermediate-risk groups, respectively (p < 0.012). Among patients with intermediate-risk disease, those considered to have low intermediate-risk (Gleason 6 with PSA >10, or Gleason 3 + 4 with PSA <10; n = 106) had a significantly higher bDFS than patients with high intermediate-risk (Gleason 3 + 4 with PSA 10–20 or Gleason 4 + 3; n = 47), with bDFS of 93.5 vs. 79.3%, respectively. For the low-risk and low intermediate-risk groups, there was no difference in median PSA nadir or biochemical disease control between doses of 35 and 36.25 Gy.Conclusion: CyberKnife SBRT produces excellent biochemical control rates. Median PSA levels compare favorably with other radiation modalities and strongly suggest durability of response. These results also strongly suggest that 35 Gy is as effective as 36.25 Gy for low- and intermediate-risk patients.