Prognostic Risk Assessment and Prediction of Radiotherapy Benefit for Women with Ductal Carcinoma In Situ (DCIS) of the Breast, in a Randomized Clinical Trial (SweDCIS).

Prediction of radiotherapy (RT) benefit after breast-conserving surgery (BCS) for DCIS is crucial. The aim was to validate a biosignature, DCISionRT®, in the SweDCIS randomized trial. Women were randomly assigned to RT or not after BCS, between 1987 and 2000. Tumor blocks were collected, and slides were sent to PreludeDxTM for testing. In 504 women with complete data and negative margins, DCISionRT divided 52% women into Elevated (DS > 3) and 48% in Low (DS ≤ 3) Risk groups. In the Elevated Risk group, RT significantly decreased relative 10-year ipsilateral total recurrence (TotBE) and 10-year ipsilateral invasive recurrence (InvBE) rates, HR 0.32 and HR 0.24, with absolute decreases of 15.5% and 9.3%. In the Low Risk group, there were no significant risk differences observed with radiotherapy. Using a cutoff of DS > 3.0, the test was not predictive for RT benefit (p = 0.093); however, above DS > 2.8 RT benefit was greater for InvBE (interaction p = 0.038). Recurrences at 10 years without radiotherapy increased significantly per 5 DS units (TotBE HR:1.5 and InvBE HR:1.5). Continuous DS was prognostic for TotBE risk although categorical DS did not reach significance. Absolute 10-year TotBE and InvBE risks appear sufficiently different to indicate that DCISionRT can aid physicians in selecting individualized adjuvant DCIS treatment strategies. Further analyses are planned in combined cohorts to increase statistical power.

Validation of a Ductal Carcinoma In Situ Biomarker Profile for Risk of Recurrence after Breast-Conserving Surgery with and without Radiotherapy.

PURPOSE: A major challenge in ductal carcinoma in situ (DCIS) treatment is selection of the most appropriate therapeutic approach for individual patients. We conducted an external prospective-retrospective clinical validation of a DCIS biologic risk signature, DCISionRT, in a population-based observational cohort of women diagnosed with DCIS and treated with breast-conserving surgery (BCS). EXPERIMENTAL DESIGN: Participants were 455 health plan members of Kaiser Permanente Northwest diagnosed with DCIS and treated with BCS with or without radiotherapy from 1990 to 2007. The biologic signature combined seven protein tumor markers assessed in formalin-fixed, paraffin-embedded tumor tissue with four clinicopathologic factors to provide a DCISionRT test result, termed decision score (DS). Cox regression and Kaplan-Meier analysis were used to measure the association of the DS, continuous (linear) or categorical (DS ≤ 3 vs. DS > 3), and subsequent total ipsilateral breast events and invasive ipsilateral breast events at least 6 months after initial surgery. RESULTS: In Cox regression, the continuous and categorical DS variables were positively associated with total and invasive breast event risk after adjustment for radiotherapy. In a subset analysis by treatment group, categorical Kaplan-Meier analyses showed at least 2-fold differences in 10-year risk of total breast events between the elevated-risk and low-risk DS categories. CONCLUSIONS: In this first external validation study of the DCISionRT test, the DS was prognostic for the risk of later breast events for women diagnosed with DCIS, following BCS.

A Biological Signature for Breast Ductal Carcinoma In Situ to Predict Radiotherapy Benefit and Assess Recurrence Risk.

PURPOSE: Ductal carcinoma in situ (DCIS) patients and their physicians currently face challenging treatment decisions with limited information about the individual's subsequent breast cancer risk or treatment benefit. The DCISionRT biological signature developed in this study provides recurrence risk and predicts radiotherapy (RT) benefit for DCIS patients following breast-conserving surgery (BCS). EXPERIMENTAL DESIGN: A biological signature that calculates an individualized Decision Score (DS) was developed and cross-validated in 526 DCIS patients treated with BCS ± RT. The relationship was assessed between DS and 10-year risk of invasive breast cancer (IBC) or any ipsilateral breast event (IBE), including IBC or DCIS. RT benefit was evaluated by risk group and as a function of DS. RESULTS: The DS was significantly associated with IBC and IBE risk, HR (per 5 units) of 4.2 and 3.1, respectively. For patients treated without RT, DS identified a Low Group with 10-year IBC risk of 4% (7% IBE) and an Elevated Risk Group with IBC risk of 15% (23% IBE). In analysis of DS and RT by group, the Elevated Risk Group received significant RT benefit, HR of 0.3 for IBC and IBE. In a clinicopathologically low-risk subset, DS reclassified 42% of patients into the Elevated Risk Group. In an interaction analysis of DS and RT, patients with elevated DS had significant RT benefit over baseline. CONCLUSIONS: The DS was prognostic for risk and predicted RT benefit for DCIS patients. DS identified a clinically meaningful low-risk group and a group with elevated 10-year risks that received substantial RT benefit over baseline.

Image analysis algorithms for immunohistochemical assessment of cell death events and fibrosis in tissue sections.

Cell death is of broad physiological and pathological importance, making quantification of biochemical events associated with cell demise a high priority for experimental pathology. Fibrosis is a common consequence of tissue injury involving necrotic cell death. Using tissue specimens from experimental mouse models of traumatic brain injury, cardiac fibrosis, and cancer, as well as human tumor specimens assembled in tissue microarray (TMA) format, we undertook computer-assisted quantification of specific immunohistochemical and histological parameters that characterize processes associated with cell death. In this study, we demonstrated the utility of image analysis algorithms for color deconvolution, colocalization, and nuclear morphometry to characterize cell death events in tissue specimens: (a) subjected to immunostaining for detecting cleaved caspase-3, cleaved poly(ADP-ribose)-polymerase, cleaved lamin-A, phosphorylated histone H2AX, and Bcl-2; (b) analyzed by terminal deoxyribonucleotidyl transferase-mediated dUTP nick end labeling assay to detect DNA fragmentation; and (c) evaluated with Masson's trichrome staining. We developed novel algorithm-based scoring methods and validated them using TMAs as a high-throughput format. The proposed computer-assisted scoring methods for digital images by brightfield microscopy permit linear quantification of immunohistochemical and histochemical stainings. Examples are provided of digital image analysis performed in automated or semiautomated fashion for successful quantification of molecular events associated with cell death in tissue sections.

Prognostic marker profile to assess risk in stage I-III hormone receptor-positive breast cancer patients.

Single markers are insufficient to accurately assess risk of relapse for adjuvant therapy guidance in operable breast cancer patients. In addition, the accuracy and interpretability of current multi-marker tests is generally limited by their simply additive algorithms and their overlap with clinicopathologic risks. Here, we report the development and validation of a nonlinear algorithm that combines protein (ER, PGR, ERBB2, BCL2 and TP53) and genomic (MYC/8q24) markers with standard clinicopathologic features (tumor size, tumor grade and nodal status) into a global risk assessment profile. The algorithm was trained using statistical pattern recognition in 200 stage I-III hormone receptor-positive patients treated with hormone therapy. Continuous risk scores (0-10+) were then generated for 232 independent patients. In hormone therapy-treated patients, the profile achieved a hazard ratio of 6.2 (95% confidence interval [CI], 1.8-20) in high- vs. low-risk groups for time to distant metastasis with the low-risk group having a 10-year metastasis rate of just 4% (95% CI, 0-8%). Similar results were achieved in untreated patients and for disease-specific survival. In multivariate analyses with standard prognostic factors and clinical practice guidelines, the profile was the only significant variable. Furthermore, the profile reclassified as low risk over half of node-negative patients at elevated risk according to the guidelines, which could have spared such patients from unnecessary cytotoxic chemotherapy. It also accurately identified a group of high-risk patients within a guideline low-risk group. In summary, the profile intelligently combines biologically relevant marker pathways and established clinicopathologic risks to help guide breast cancer patients to the most appropriate level of adjuvant therapy.

A multimarker model to predict outcome in tamoxifen-treated breast cancer patients.

PURPOSE: This study was designed to produce a model to predict outcome in tamoxifen-treated breast cancer patients based on clinicopathologic features and multiple molecular markers. EXPERIMENTAL DESIGN: This was a retrospective study of 324 stage I to III female breast cancer patients treated with tamoxifen for whom standard clinicopathologic data and tumor tissue microarrays were available. Nine molecular markers were studied by semiquantitative immunohistochemistry and/or fluorescence in situ hybridization. Cox proportional hazards analysis was used to determine the contributions of each variable to disease-specific and overall survival, and machine learning was used to produce a model to predict patient outcome. RESULTS: On a univariate basis, the following features were significantly associated with worse survival: high pathologic tumor or nodal class, histologic grade, epidermal growth factor receptor, ERBB2, MYC, or TP53; absent estrogen receptor (ER) or progesterone receptor; and low BCL2. CCND1 and CDKN1B did not reach statistical significance. On a multivariate basis, nodal class, ER, and MYC were statistically significant as independent factors for survival. However, the benefit of ER-positive status was moderated by BCL2, ERBB2, and progesterone receptor. BCL2 and TP53 also interacted as an independent risk factor. A kernel partial least squares polynomial model was developed with an area under the receiver operating characteristic curve of 0.90. CONCLUSIONS: Our data show the predictive value of BCL2, ERBB2, MYC, and TP53 in addition to the standard hormone receptors and clinicopathologic features, and they show the importance of conditional interpretation of certain molecular markers. Our multimarker predictive model performed significantly better than standard guidelines.

BLM helicase facilitates Mus81 endonuclease activity in human cells.

Bloom syndrome is a rare, autosomal recessive inherited disorder in humans. The product of the Bloom syndrome mutated gene, designated BLM, is a member of the RecQ helicase family. BLM has been proposed to function at the interface of replication and recombination, and to facilitate the repair of DNA damage. Here, we report in vivo physical interaction and colocalization of BLM and a DNA structure-specific endonuclease, Mus81, at sites of stalled replication forks outside the promyelocytic leukemia nuclear bodies during the S-phase arrest of the cell cycle. Amino acids 125 to 244 of Mus81 interact with the C-terminal region (amino acids 1,007-1,417) of BLM. Whereas Mus81 does not have any effect on the helicase activity of BLM, BLM can stimulate Mus81 endonuclease activity on the nicked Holliday junctions and 3' flap. This stimulation is due to enhanced binding of Mus81 to the DNA substrates. These data suggest a new function of BLM in cooperating with Mus81 during processing and restoration of stalled replication forks.

Functional interaction between BLM helicase and 53BP1 in a Chk1-mediated pathway during S-phase arrest.

Bloom's syndrome is a rare autosomal recessive genetic disorder characterized by chromosomal aberrations, genetic instability, and cancer predisposition, all of which may be the result of abnormal signal transduction during DNA damage recognition. Here, we show that BLM is an intermediate responder to stalled DNA replication forks. BLM colocalized and physically interacted with the DNA damage response proteins 53BP1 and H2AX. Although BLM facilitated physical interaction between p53 and 53BP1, 53BP1 was required for efficient accumulation of both BLM and p53 at the sites of stalled replication. The accumulation of BLM/53BP1 foci and the physical interaction between them was independent of gamma-H2AX. The active Chk1 kinase was essential for both the accurate focal colocalization of 53BP1 with BLM and the consequent stabilization of BLM. Once the ATR/Chk1- and 53BP1-mediated signal from replicational stress is received, BLM functions in multiple downstream repair processes, thereby fulfilling its role as a caretaker tumor suppressor.

The mismatch DNA repair heterodimer, hMSH2/6, regulates BLM helicase.

The human MSH2/6 complex is essential for mismatch recognition during the repair of replication errors. Although mismatch repair components have been implicated in DNA homologous recombination repair, the exact function of hMSH2/6 in this pathway is unclear. Here, we show that the recombinant hMSH2/6 protein complex stimulated the ability of the Bloom's syndrome gene product, BLM, to process Holliday junctions in vitro, an activity that could also be regulated by p53. Consistent with these observations, hMSH6 colocalized with BLM and phospho-ser15-p53 in hydroxyurea-induced RAD51 nuclear foci that may correspond to the sites of presumed stalled DNA replication forks and more likely the resultant DNA double-stranded breaks. In addition, we show that hMSH2 and hMSH6 coimmunoprecipitated with BLM, p53, and RAD51. Both the number of RAD51 foci and the amount of the BLM-p53-RAD51 complex are increased in hMSH2- or hMSH6-deficient cells. These data suggest that hMSH2/6 formed a complex with BLM-p53-RAD51 in response to the damaged DNA forks during double-stranded break repair.

Involvement of Crm1 in hepatitis B virus X protein-induced aberrant centriole replication and abnormal mitotic spindles.

Hepatitis B virus (HBV) includes an X gene (HBx gene) that plays a critical role in liver carcinogenesis. Because centrosome abnormalities are associated with genomic instability in most human cancer cells, we examined the effect of HBx on centrosomes. We found that HBx induced supernumerary centrosomes and multipolar spindles. This effect was independent of mutations in the p21 gene. Furthermore, the ability of HBV to induce supernumerary centrosomes was dependent on the presence of physiological HBx expression. We recently showed that HBx induces cytoplasmic sequestration of Crm1, a nuclear export receptor that binds to Ran GTPase, thereby inducing nuclear localization of NF-kappaB. Consistently, supernumerary centrosomes were observed in cells treated with a Crm1-specific inhibitor but not with an HBx mutant that lacked the ability to sequester Crm1 in the cytoplasm. Moreover, a fraction of Crm1 was found to be localized at the centrosomes. Immunocytochemical and ultrastructural examination of these supernumerary centrosomes revealed that inactivation of Crm1 was associated with abnormal centrioles. The presence of more than two centrosomes led to an increased frequency of defective mitoses and chromosome transmission errors. Based on this evidence, we suggest that Crm1 is actively involved in maintaining centrosome integrity and that HBx disrupts this process by inactivating Crm1 and thus contributes to HBV-mediated carcinogenesis.

p53 interacts with hRAD51 and hRAD54, and directly modulates homologous recombination.

p53 inhibits tumorigenesis through a variety of functions, including mediation of cell cycle arrest, premature senescence, and apoptosis.p53 also can associate with several DNA helicases and proteins involved in homologous recombination. In this study, we show that p53, hRAD51, and hRAD54 coimmunoprecipitated and colocalized with each other at endogenous levels in normal cells. Colocalization was observed with the phosphoserine-15 form of p53 at presumed DNA processing sites after the induction of DNA breaks. hRAD54 bound directly to the p53 COOH terminus in vitro without a nucleic acid intermediate. We then investigated the functional consequences of these protein interactions. A host cell reactivation assay revealed that the elevation in recombination observed after p53 inactivation is dependent on the hRAD51 pathway and that p53-dependent antirecombinogenic activity can be attributed to p53 binding to hRAD51 directly. These data support the hypothesis that p53 helps maintain genetic stability through transcription-independent modulation of homologous recombination factors.

Human malignant glioma cell lines are sensitive to low radiation doses.

Malignant gliomas display aggressive local behavior and are not cured by existing therapy. Some cell lines that are considered radioresistant respond to low radiation doses (<1 Gy) with increased cell killing (low-dose hypersensitivity). In our study, 4 of 5 human glioma cell lines exhibited significant X-ray sensitivity at doses below 1 Gy. The surviving fractions (SFs) obtained at 0.7 and/or 0.8 Gy were comparable to those at 1.5 Gy. Low-dose hypersensitivity was evident when irradiation was combined with etoposide treatment. Repeated irradiation with low doses was markedly more effective than irradiation with single, biologically equivalent doses in decreasing SFs, inhibiting xenograft tumor growth in mice. All experiments were conducted with an accelerator used in clinics, establishing that low-dose hypersensitivity was present following megavoltage X-irradiation. Thus, repeated low-dose irradiation (ultrafractionation) could greatly improve the effectiveness of radiotherapy of gliomas and could allow safe treatment of patients with cumulative doses greater than 60 Gy.

UV-C-induced DNA damage leads to p53-dependent nuclear trafficking of PML.

The promyelocytic leukemia protein (PML) is a nuclear phosphoprotein that localizes to distinct domains in the nucleus, described as PML nuclear bodies (PML-NBs). Recent findings indicate that PML regulates the p53 response to oncogenic signals. Here, we define a p53-dependent role for PML in response to DNA damage. We exposed cells to ultraviolet light (UV-C) and imaged the nuclear distribution of PML, p53, and the BLM helicase by confocal microscopy. After DNA damage, PML partially relocated out of the PML-NBs, and colocalized with BLM and p53 at sites of DNA repair. In addition, using the isogenic HCT116 cell lines (p53+/+ and -/-), we show that the redistribution of PML was dependent on functional p53. Western analysis revealed that the level of PML protein remained unaltered after UV-C treatment. These results are consistent with the hypothesis that PML, in conjunction with p53 and BLM, contributes to the cellular response to UV-C-induced DNA damage and its repair.

BLM helicase-dependent transport of p53 to sites of stalled DNA replication forks modulates homologous recombination.

Diverse functions, including DNA replication, recombination and repair, occur during S phase of the eukaryotic cell cycle. It has been proposed that p53 and BLM help regulate these functions. We show that p53 and BLM accumulated after hydroxyurea (HU) treatment, and physically associated and co-localized with each other and with RAD51 at sites of stalled DNA replication forks. HU-induced relocalization of BLM to RAD51 foci was p53 independent. However, BLM was required for efficient localization of either wild-type or mutated (Ser15Ala) p53 to these foci and for physical association of p53 with RAD51. Loss of BLM and p53 function synergistically enhanced homologous recombination frequency, indicating that they mediated the process by complementary pathways. Loss of p53 further enhanced the rate of spontaneous sister chromatid exchange (SCE) in Bloom syndrome (BS) cells, but not in their BLM-corrected counterpart, indicating that involvement of p53 in regulating spontaneous SCE is BLM dependent. These results indicate that p53 and BLM functionally interact during resolution of stalled DNA replication forks and provide insight into the mechanism of genomic fidelity maintenance by these nuclear proteins.

Nitric oxide-induced cellular stress and p53 activation in chronic inflammation.

Free radical-induced cellular stress contributes to cancer during chronic inflammation. Here, we investigated mechanisms of p53 activation by the free radical, NO. NO from donor drugs induced both ataxia-telangiectasia mutated (ATM)- and ataxia-telangiectasia mutated and Rad3-related-dependent p53 posttranslational modifications, leading to an increase in p53 transcriptional targets and a G(2)M cell cycle checkpoint. Such modifications were also identified in cells cocultured with NO-releasing macrophages. In noncancerous colon tissues from patients with ulcerative colitis (a cancer-prone chronic inflammatory disease), inducible NO synthase protein levels were positively correlated with p53 serine 15 phosphorylation levels. Immunostaining of HDM-2 and p21(WAF1) was consistent with transcriptionally active p53. Our study highlights a pivotal role of NO in the induction of cellular stress and the activation of a p53 response pathway during chronic inflammation.

The p53 network in lung carcinogenesis.

The p53 tumor suppressor gene lies at the crossroads of multiple cellular response pathways that control a cell's fate in response to endogenous or exogenous stresses. Positive and negative regulatory loops both upstream and downstream of p53 cooperate to finely tune its functions as a transcription factor, a DNA damage sensor, and possibly, a protein-assembly scaffold. Through this plethora of activities, p53 is a major determinant of cell survival and a safeguard against genetic instability. Functional inactivation of p53 pathways through genetic and epigenetic events affecting the p53 gene itself and/or its interacting partners occur with a high frequency in lung cancer. The p53 mutational spectrum provides molecular evidence of the etiology of lung cancer and supports abundant epidemiological data indicating the role of tobacco smoke in the causation of this disease.

The processing of Holliday junctions by BLM and WRN helicases is regulated by p53.

BLM, WRN, and p53 are involved in the homologous DNA recombination pathway. The DNA structure-specific helicases, BLM and WRN, unwind Holliday junctions (HJ), an activity that could suppress inappropriate homologous recombination during DNA replication. Here, we show that purified, recombinant p53 binds to BLM and WRN helicases and attenuates their ability to unwind synthetic HJ in vitro. The p53 248W mutant reduces abilities of both to bind HJ and inhibit helicase activities, whereas the p53 273H mutant loses these abilities. Moreover, full-length p53 and a C-terminal polypeptide (residues 373-383) inhibit the BLM and WRN helicase activities, but phosphorylation at Ser(376) or Ser(378) completely abolishes this inhibition. Following blockage of DNA replication, Ser(15) phospho-p53, BLM, and RAD51 colocalize in nuclear foci at sites likely to contain DNA replication intermediates in cells. Our results are consistent with a novel mechanism for p53-mediated regulation of DNA recombinational repair that involves p53 post-translational modifications and functional protein-protein interactions with BLM and WRN DNA helicases.