Type I interferons (IFNs) are important enhancers of immune responses which are downregulated in human cancers, including skin cancer. Solar ultraviolet (UV) B radiation is a proven environmental carcinogen, and its exposure contributes to the high prevalence of skin cancer. The carcinogenic effects of UV light can be attributed to the formation of cyclobutane pyrimidine dimers (CPD) and errors in the repair and replication of DNA. Treatment with a single dose of UVB (100 mJ/cm2) upregulated IFNα and IFNβ in the skin of C57BL/6 mice. IFNα and IFNβ were predominantly produced by CD11b+ cells. In mice lacking the type I IFN receptor 1 (IFNAR1), the repair of CPD following cutaneous exposure to a single dose of UVB (100 mJ/cm2) was decreased. UVB induced the expression of the DNA repair gene xeroderma pigmentosum A (XPA) in wild-type (WT) mice. In contrast, such treatment in IFNAR1 (IFNAR1-/-) mice downregulated XPA. A local UVB regimen consisting of UVB radiation (150 mJ/cm2) for 4 days followed by sensitization with hapten 2,4, dinitrofluorobenzene (DNFB) resulted in significant suppression of immune responses in both WT and IFNAR1-/- mice. However, there were significantly higher CD4+CD25+Foxp3+ regulatory T-cells in the draining lymph nodes of IFNAR1-/- mice in comparison to WT mice. Overall, our studies reveal a previously unknown action of type I IFNs in the repair of photodamage and the prevention of UVB-induced immune suppression.
Abstract Metastasis continues to be the most difficult clinical challenge for breast cancer. These patients have unacceptable survival rates that have not changed in the past 20 years. Therefore, more effective therapeutic options are needed. The purpose of this study is to better understand molecular mechanisms of the SIN3 chromatin complexes that have been functionally associated with breast cancer progression to identify novel targeting strategies. Alteration of the composition of SIN3 complexes regulates the metastatic potential of breast cancer cells; and inhibition of SIN3 complexes induces differentiation and inhibits invasion of breast cancer cells. However, differences in the function of SIN3 isoforms (SIN3A and SIN3B) in breast cancer metastasis have not been characterized. To better define the role of SIN3 isoforms in breast cancer metastasis, we generated stable knockdown of SIN3 isoforms individually and in combination using 3 non-overlapping shRNA in two different metastatic breast cancer cell lines (MDA-MB-231 and -435). No significant change was noted in the proliferation rate of the transduced cells in vitro. Stable knockdown of SIN3B caused a significant decrease in invasion through Matrigel (28 ± 4 invaded cells/field compared to 50 ± 8 for control; p = 0.027) using a modified Boyden chamber that was corroborated by the decreased presence of stellate projections and a more epithelial phenotypic growth in 3D. Surprisingly, stable knockdown of SIN3A significantly increased invasion through Matrigel (98 ± 14 invaded cells/field; p = 0.008) and increased the presence of stellate projections in the 3D growth assay. Dual knockdown of SIN3A and SIN3B caused a significant decrease in invasiveness (19 ± 5 invaded cells/field; p = 0.003) and decreased presence of stellate projections similar to the phenotype noted with individual knockdown of SIN3B. These results were confirmed in vivo with an experimental metastasis assay (lateral tail vein injection in athymic nude mice) in which SIN3B knockdown significantly decreased lung metastasis (70% decrease compared to control; p = 0.009) and SIN3A knockdown increased metastasis (163% increase compared to control; p = 0.096). These results demonstrate key functional differences between SIN3 isoforms in regulating the process of metastasis. Our data suggests metastasis suppressive roles of SIN3A and metastasis promoting roles of SIN3B that will be important in discovering novel therapeutic strategies for metastatic breast cancer patients. Citation Format: Monica J. Lewis, Jianzhong Liu, Douglas R. Hurst. Defining roles of SIN3 isoforms in breast cancer metastasis. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2267. doi:10.1158/1538-7445.AM2015-2267
Abstract Each year, an unacceptable number of deaths occur in women because of the lack of curative approaches for metastatic breast cancer. Some of the key regulators of breast cancer progression are molecules within the tumor microenvironment including adipokines, a broad array of autocrine-, endocrine-, and paracrine-acting bioactive molecules secreted by adipocytes. Adiponectin is one of the most abundant adipokines and, while multiple widely cited epidemiological studies have indicated that low levels of circulating plasma adiponectin portend poorer prognosis, recent work has reported that elevated adiponectin expression in breast tissue is, in fact, correlated with more advanced disease. Thus, the purpose of this work is to better understand how adiponectin in breast tissue acts directly on tumor cells to regulate the early steps of breast cancer metastasis. Our hypothesis is that adiponectin alters metastatic potential of breast cancer cells via induction of autophagy. To begin to test this premise, we discerned the effect of globular versus full-length adiponectin on invasive and migratory phenotypes of a human metastatic breast cancer cell line (MDA-MB-231). In transwell assays with and without Matrigel, globular adiponectin increased invasion (91%; p < 0.001) and migration (222%; p < 0.05) compared to untreated cells, whereas full length adiponectin had no significant effect. Rapamycin, an established autophagy inducer, elicited effects similar to globular adiponectin (increase of 210%; p < 0.001 in invasion and 238%; p < 0.05 in migration). Likewise, three-dimensional growth in Matrigel revealed that cells treated with globular adiponectin and rapamycin developed extended spikes indicative of a more invasive phenotype, whereas those treated with full-length adiponectin maintained a less invasive grape-like structure. Neither adiponectin isoform altered proliferation. Biochemical assays of autophagic induction supported these observations, demonstrating increases in LC3B-II expression (immunoblot) and in the number of intracellular LC3B puncta (immunofluorescence) upon treatment with globular, but not full-length, adiponectin. Together, these results suggest a plausible model linking a specific adiponectin isoform with induction of autophagy to stimulate breast cancer metastasis. Our findings will advance the field by revealing distinct, novel roles for key microenvironmental regulatory molecules, potentially opening up new avenues for therapeutic development. This work is timely considering recent interest in adiponectin and adiponectin receptor agonists as therapeutic strategies. In addition, noting that an aberrant level of adiponectin is a putative mechanism linking obesity to poor breast cancer prognosis and metastasis, our results may provide mechanistic insight to guide lifestyle interventions that will reduce breast cancer's heavy morbidity and mortality burden. Citation Format: Emily Falk Libby, Jianzhong Liu, Monica J. Lewis, Andra R. Frost, Wendy Demark-Wahnefried, Douglas R. Hurst. Regulation of metastatic potential through adiponectin-stimulated induction of autophagy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 989. doi:10.1158/1538-7445.AM2015-989
Breast cancer cells are heterogeneous in their ability to invade and fully metastasize, and thus also in their capacity to survive the numerous stresses encountered throughout the multiple steps of the metastatic cascade. Considering the role of autophagy as a survival response to stress, the present study hypothesized that distinct populations of breast cancer cells may possess an altered autophagic capacity that influences their metastatic potential. It was observed that a metastatic breast cancer cell line, MDA‑MB‑231, that was sensitive to autophagic induction additionally possessed the ability to proliferate following nutrient deprivation. Furthermore, a selected subpopulation of these cells that survived multiple exposures to starvation conditions demonstrated a heightened response to autophagic induction compared to their parent cells. Although this subpopulation maintained a more grape‑like pattern in three‑dimensional culture compared to the extended spikes of the parent population, autophagic induction in this subpopulation elicited an invasive phenotype with extended spikes. Taken together, these results suggest that autophagic induction may contribute to the ability of distinct breast cancer cell populations to survive and invade.
Abstract Autophagy is a catabolic process that is tightly regulated during normal cell growth, development, and homeostasis. Although it may be death inducing, it is also an important survival mechanism for cells in stressful environments, including hypoxia, nutrient deprivation, chemical or physical pressure, or detachment from colonies. Considering the stress associated with the process of metastasis, we hypothesized that autophagy may play a role in the ability of breast cancer cells to survive and metastasize. To test this, we first compared cell proliferation after autophagic induction between metastatic breast cancer cell lines (MDA-MB-231 and -435), a non-metastatic breast cancer cell line (MDA-MB-436), and a ‘normal’ breast epithelial cell line (MCF10A). Both metastatic cell lines continued to proliferate following induction of autophagy; however, the non-metastatic and normal cell lines were growth-inhibited. Autophagy was also more rapidly induced by rapamycin in the metastatic cell lines as demonstrated by an increase in LC3II expression. To test the different survival capabilities between metastatic and normal cells, we selected cells through five rounds of starvation with Earle's balanced salt solution (EBSS) and compared their ability to induce autophagy. Although both the normal and metastatic cells maintained their ability to proliferate under normal conditions, the MDA-MB-231 cells that survived starvation (231-EB5) proliferated more rapidly than the parental population following induction of autophagy. In contrast, both MCF10A and MCF10A-EB5 cells were growth-inhibited. The 231-EB5 cells induced autophagy more rapidly than the parental population as demonstrated by increased expression of LC3II (analyzed by immunoblot) and increased LC3 puncta (analyzed by immunofluorescence). Migration of parental 231 cells was inhibited by rapamycin; however, there was no change in the ability of 231-EB5 cells to migrate after treatment with rapamycin. Growth in three dimensions also was significantly altered. MCF10A-EB5 cells were more extended compared to the spherical growth of the parental MCF10A cells. Protrusions emitted from the 231-EB5 cells were more rounded compared to the extended spikes of the parental 231 cells. Altogether, these results demonstrate that select populations derived from metastatic breast cancer cells have different abilities to survive, proliferate, and migrate following induction of autophagy, suggesting that autophagy may be a key mechanism for tumor progression and metastasis. Citation Format: Yi Li, Monica J. Lewis, Jianzhong Liu, James J. Cody, Douglas R. Hurst. Metastatic breast cancer cell phenotype is regulated by autophagy. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1678. doi:10.1158/1538-7445.AM2013-1678
Abstract Psoriasis is a chronic inflammatory skin disease affecting 2.5–6 million patients in the United States. The cause of psoriasis remains unknown. Previous human and animal studies suggest that patients with a susceptible genetic background and some stimulus, such as barrier disruption, leads to a coordinated signaling events involving cytokines between keratinocytes, endothelial cells, T cells, macrophages and dendritic cells. Ceramides are endogenous skin lipids essential for maintaining skin barrier function and loss of ceramides may underlie inflammatory and premalignant skin. Ceramides act as a double-edged sword, promoting normal skin homeostasis in the native state, but can be metabolized to sphingosine-1-phosphate (S1P), linked to inflammation and tumorigenesis. To overcome this difficulty, we synthesized solenopsin analogs which biochemically act as ceramides, but cannot be metabolized to S1P. We assess their in vivo bioactivity in a well-established mouse model of psoriasis, the KC-Tie2 mouse. Topical solenopsin derivatives normalized cutaneous hyperplasia in this model, decreased T cell infiltration, interleukin (IL)-22 transcription, and reversed the upregulation of calprotectin and Toll-like receptor (TLR) 4 in inflamed skin. Finally, they stimulated interleukin (IL)-12 production in skin dendritic cells. Thus suggesting barrier restoration has both a biochemical and physical component, and both are necessary for optimal barrier restoration.
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