Faculty Bibliography

High-grade glioma (HGG), a deadly primary brain malignancy, manifests radioresistance mediated by cell-intrinsic and microenvironmental mechanisms. High levels of the cytokine transforming growth factor-beta (TGF-beta) in HGG promote radioresistance by enforcing an effective DNA damage response and supporting glioma stem cell self-renewal. Our analysis of HGG TCGA data and immunohistochemical staining of phosphorylated Smad2, which is the main transducer of canonical TGF-beta signaling, indicated variable levels of TGF-beta pathway activation across HGG tumors. These data suggest that evaluating the putative benefit of inhibiting TGF-beta during radiotherapy requires personalized screening. Thus, we used explant cultures of seven HGG specimens as a rapid, patient-specific ex vivo platform to test the hypothesis that LY364947, a small molecule inhibitor of the TGF-beta type I receptor, acts as a radiosensitizer in HGG. Immunofluorescence detection and image analysis of gamma-H2AX foci, a marker of cellular recognition of radiation-induced DNA damage, and Sox2, a stem cell marker that increases post-radiation, indicated that LY364947 blocked these radiation responses in five of seven specimens. Collectively, our findings suggest that TGF-beta signaling increases radioresistance in most, but not all, HGGs. We propose that short-term culture of HGG explants provides a flexible and rapid platform for screening context-dependent efficacy of radiosensitizing agents in patient-specific fashion. This time- and cost-effective approach could be used to personalize treatment plans in HGG patients.

E-cadherin is a cell adhesion molecule best known for its function in suppressing tumor progression and metastasis. Here we show that E-cadherin promotes nucleotide excision repair through positively regulating the expression of xeroderma pigmentosum complementation group C (XPC) and DNA damage-binding protein 1 (DDB1). Loss of E-cadherin activates the E2F4 and p130/107 transcription repressor complexes to suppress the transcription of both XPC and DDB1 through activating the transforming growth factor-beta (TGF-beta) pathway. Adding XPC or DDB1, or inhibiting the TGF-beta pathway, increases the repair of ultraviolet (UV)-induced DNA damage in E-cadherin-inhibited cells. In the mouse skin and skin tumors, UVB radiation downregulates E-cadherin. In sun-associated premalignant and malignant skin neoplasia, E-cadherin is downregulated in association with reduced XPC and DDB1 levels. These findings demonstrate a crucial role of E-cadherin in efficient DNA repair of UV-induced DNA damage, identify a new link between epithelial adhesion and DNA repair and suggest a mechanistic link of early E-cadherin loss in tumor initiation.Oncogene advance online publication, 19 October 2015; doi:10.1038/onc.2015.390.

Current knowledge of stem cell characteristics, maintenance and renewal, evolution with age, location in 'niches', and radiosensitivity to acute and protracted exposures is reviewed regarding haematopoietic tissue, mammary gland, thyroid, digestive tract, lung, skin, and bone. The identity of the target cells for carcinogenesis continues to point to the more primitive and mostly quiescent stem cell population (able to accumulate the protracted sequence of mutations necessary to result in malignancy), and, in a few tissues, to daughter progenitor cells. Several biological processes could contribute to the protection of stem cells from mutation accumulation: (1) accurate DNA repair; (2) rapid induced death of injured stem cells; (3) retention of the intact parental strand during divisions in some tissues so that mutations are passed to the daughter differentiating cells; and (4) stem cell competition, whereby undamaged stem cells outcompete damaged stem cells for residence in the vital niche. DNA repair mainly operates within a few days of irradiation, while stem cell replications and competition require weeks or many months depending on the tissue type. This foundation is used to provide a biological insight to protection issues including the linear-non-threshold and relative risk models, differences in cancer risk between tissues, dose-rate effects, and changes in the risk of radiation carcinogenesis by age at exposure and attained age.

The tumor microenvironment (TME) represents a milieu that enables tumor cells to acquire the hallmarks of cancer. The TME is heterogeneous in composition and consists of cellular components, growth factors, proteases, and extracellular matrix. Concerted interactions between genetically altered tumor cells and genetically stable intratumoral stromal cells result in an "activated/reprogramed" stroma that promotes carcinogenesis by contributing to inflammation, immune suppression, therapeutic resistance, and generating premetastatic niches that support the initiation and establishment of distant metastasis. The lungs present a unique milieu in which tumors progress in collusion with the TME, as evidenced by regions of aberrant angiogenesis, acidosis and hypoxia. Inflammation plays an important role in the pathogenesis of lung cancer, and pulmonary disorders in lung cancer patients such as chronic obstructive pulmonary disease (COPD) and emphysema, constitute comorbid conditions and are independent risk factors for lung cancer. The TME also contributes to immune suppression, induces epithelial-to-mesenchymal transition (EMT) and diminishes efficacy of chemotherapies. Thus, the TME has begun to emerge as the "Achilles heel" of the disease, and constitutes an attractive target for anti-cancer therapy. Drugs targeting the components of the TME are making their way into clinical trials. Here, we will focus on recent advances and emerging concepts regarding the intriguing role of the TME in lung cancer progression, and discuss future directions in the context of novel diagnostic and therapeutic opportunities.

Clear mechanistic understanding of the biological processes elicited by radiation that increase cancer risk can be used to inform prediction of health consequences of medical uses, such as radiotherapy, or occupational exposures, such as those of astronauts during deep space travel. Here, we review the current concepts of carcinogenesis as a multicellular process during which transformed cells escape normal tissue controls, including the immune system, and establish a tumor microenvironment. We discuss the contribution of two broad classes of radiation effects that may increase cancer: radiation targeted effects that occur as a result of direct energy deposition, e.g., DNA damage, and non-targeted effects (NTE) that result from changes in cell signaling, e.g., genomic instability. It is unknown whether the potentially greater carcinogenic effect of high Z and energy (HZE) particle radiation is a function of the relative contribution or extent of NTE or due to unique NTE. We addressed this problem using a radiation/genetic mammary chimera mouse model of breast cancer. Our experiments suggest that NTE promote more aggressive cancers, as evidenced by increased growth rate, transcriptomic signatures, and metastasis, and that HZE particle NTE are more effective than reference gamma-radiation. Emerging evidence suggest that HZE irradiation dampens antitumor immunity. These studies raise concern that HZE radiation exposure not only increases the likelihood of developing cancer but also could promote progression to more aggressive cancer with a greater risk of mortality.

Background: Data from the Consortium of Investigators of Modifiers of BRCA1/2 (CIMBA) indicates that common variation in the BRCA1 locus modifies the penetrance of mutations. The rs5820483 variation is one such polymorphism in which patients homozygous for the major allele have a greater risk of breast cancer. The BRCA1 gene contains 24 exons that generate a full-length (FL) protein. Major alternatively spliced isoforms include skipping of exon 11 (DELTA11) and a truncated form (IRIS), each of which appear to have distinct roles in cellular processes. rs5820483 is the only variant that maps to intron 10, flanking exon 11. Experimental models suggest that deregulation of the FL/D11 isoform ratio can have profound functional consequences. We have shown that cells from patients with the major rs5820483 allele express more FL relative to DELTA11 compared to cells from patients with the minor allele. Breast cancer exhibit increased IGF-1 and IGF-1 activity in patients with BRCA1 mutations relative to breast cancer in women without BRCA1 mutations. IGF-1 produced in the mammary stroma mediates estrogen dependent proliferation. Here we test whether the rs5820483 allele affects IGF-1 activity in breast tissue of BRCA1 mutation carriers. Design: We assessed the zygosity of the rs5820483 alleles in 28 BRCA1 mutation carriers. Phosphorylated IGF-1 receptor (p-IGF-1R rabbit polyclonal Ab39398, Abcam, MA) was measured by immunofluorescence and Ki-67 was measured by immunohistochemistry in sections from histologically normal breast tissue from these cases were compared to heterozygous controls. Image analysis was used to assess the intensity of the p-IGF-1R immunofluorescence at the epithelial cell membrane with appropriate controls. Ki67 mmunohistochemistry was also performed on these specimens. Results:The rs5820483 allele was heterozygous in 10 specimens, homozygous for the major allele in 11 and homozygous for the minor allele in 7. The intensity of p-IGF-1R was higher in major homozygous cases (140+/-54 SD) than in either the minor homozygous (99+/-24) or heterozygous cases (95+/-44). The frequency of Ki-67+ cells was higher in the major homozygous case (3.1+/-2.9 SD) than in either the minor homozygous (1.5+/-1.9 SD) or heterozygous cases (2.2+/-2.5 SD). However, neither p-IGF-IR immunoreactivity nor frequency of Ki-67+ cells was statistically different between groups. Conclusion: Breast cancer risk in BRCA1 mutation carriers is modified by common genetic variation at the corresponding locus. We have identified a variation at rs5820483 that affects the isoform ratio. Our preliminary analysis suggests that IGF-1 activity increases in those women homozygous for the major allele, concomitant with increased Ki-67. Corroboration of this analysis in a larger series is ongoing. A statistically significant difference might have fundamental implications for cancer prevention in those carriers