Previous studies have documented that the ability to heal wounds declines with age. Although many factors contribute to this age-associated deficit, one variable that has not been carefully examined is leukocyte recruitment and function in wounds. This investigation compares the inflammatory response in excisional wounds of young (age 8 wk) and aged (age 22 mo) mice. In the early inflammatory response, neutrophil content of wounds was similar for both aged and young mice. In contrast, macrophage levels were 56% higher in aged versus young mice (81 +/- 20 vs 52 +/- 13 cells per mm2). In the later inflammatory response, wounds of aged mice exhibited a delay in T cell infiltration, with maximum T cell levels at day 10 in aged mice versus day 7 in young mice. Despite this delay, the eventual peak concentration of T cells was 23% higher in the wounds of aged mice (152 +/- 11 cells per mm2 vs 124 +/- 21cells per mm2). The observed alterations in inflammatory cell content suggested that chemokine production might be altered with age. An elevation of monocyte chemoattractant protein (MCP-1) levels was observed in wounds of aged mice. RNase protection studies, however, revealed that the production of most chemokines, including MIP-2, MIP-1alpha, MIP-1beta, and eotaxin, tended to decline with age. Because optimal wound healing requires both appropriate macrophage infiltration and phagocytic activity, phagocytosis was examined. Compared to young mice, wound macrophages from aged mice exhibited a 37%-43% reduction in phagocytic capacity. Taken together, the data demonstrate age-related shifts in both macrophage and T cell infiltration into wounds, alterations in chemokine content, and a concurrent decline in wound macrophage phagocytic function. These alterations may contribute to the delayed repair response of aging.

Treatment with chemotherapy or radiation is not invariably cytotoxic to all tumor cells. Some of the cells that survive treatment recover and resume proliferation, whereas others undergo permanent growth arrest. To understand the nature of treatment-induced terminal growth arrest, colon carcinoma cells were exposed to doxorubicin, and surviving cells were separated into proliferating and growth-arrested populations.

Cell senescence is a physiological program of terminal growth arrest, which is believed to play an important role in cancer prevention. Senescent cells secrete multiple growth-regulatory proteins, some of which can affect tumor growth, survival, invasion, or angiogenesis. Changes in expression of different senescence-associated genes were analyzed in cultured human skin keratinocytes (KCs) that underwent replicative senescence or confluence-induced accelerated senescence. Senescent KC cultures showed a strong increase in mRNA and protein expression of maspin, a member of serine protease inhibitor family and an epithelial cell tumor suppressor with anti-invasive and antiangiogenic activities. Immunohistochemical analysis of 14 normal human skin samples (age range from 3 months to 84 years) showed that maspin is expressed by KCs in vivo and that the extent and intensity of maspin expression in the skin is significantly (P ‫؍‬ 0.01) correlated with chronological age. Antiangiogenic activity of maspin secreted by senescent KCs was investigated in vitro by testing the effect of conditioned media from different KC cultures on endothelial cell migration in the presence or absence of several angiogenic factors. Media conditioned by senescent cultures (undergoing replicative or accelerated senescence), but not by proliferating KCs, strongly inhibited the stimulation of endothelial cell migration by all of the tested angiogenic factors. Neutralizing antibody against maspin abrogated this effect of conditioned media. These findings indicate that senescent KCs exert a paracrine antiangiogenic activity, and maspin is the principal contributor to this potentially tumor-suppressive effect of cellular senescence.

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We previously reported the existence of a truncated isoform of the retinoic acid receptor beta, termed beta prime. Beta prime lacks the N-terminal domains of beta 2 and beta 4, including the DNA-binding domain. However, beta prime is able to heterodimerize and interact with transcription cofactors. To determine the effects of different retinoic acid receptor isoforms on cell proliferation and apoptosis, we transduced retinoid sensitive (MCF7) and retinoid-resistant (MDA-MB-231) cells with retinoic acid receptor beta 2, beta 4, or beta prime. Expression of the truncated beta prime isoform induces resistance to retinoic acid treatment in retinoid sensitive MCF7 cells. In both retinoid sensitive and resistant cells, expression of full-length beta 2 and beta 4 isoforms results in elevated sensitivity to retinoic acid treatment and caspase-independent cell death. Cell death in beta 4 transduced MDA-MB-231 cells was accompanied by metaphase chromosome decondensation and breakage suggestive of mitotic catastrophe. Our results provide evidence that: (a) the truncated form of the retinoic acid receptor beta induces retinoid resistance rather than sensitivity; and (b) alternative pathways of cell death are mediated by different isoforms in breast cancer cells.

BackgroundThe retinoic acid receptor beta 2 (RARβ2) gene modulates proliferation and survival of cultured human breast cancer cells. Previously we showed that ectopic expression of RARβ2 in a mouse xenograft model prevented metastasis, even in the absence of the ligand, all-trans retinoic acid. We investigated both cultured cells and xenograft tumors in order to delineate the gene expression profiles responsible for an antimetastatic phenotype.MethodsRNA from MDA-MB-435 human breast cancer cells transduced with RARβ2 or empty retroviral vector (LXSN) was analyzed using Agilent Human 1A Oligo microarrays. The one hundred probes with the greatest differential intensity (p < 0.004, jointly) were determined by selecting the top median log ratios from eight-paired microarrays. Validation of differences in expression was done using Northern blot analysis and quantitative RT-PCR (qRT-PCR). We determined expression of selected genes in xenograft tumors.ResultsRARβ2 cells exhibit gene profiles with overrepresentation of genes from Xq28 (p = 2 × 10-8), a cytogenetic region that contains a large portion of the cancer/testis antigen gene family. Other functions or factors impacted by the presence of exogenous RARβ2 include mediators of the immune response and transcriptional regulatory mechanisms. Thirteen of fifteen (87%) of the genes evaluated in xenograft tumors were consistent with differences we found in the cell cultures (p = 0.007).ConclusionAntimetastatic RARβ2 signalling, direct or indirect, results in an elevation of expression for genes such as tumor-cell antigens (CTAG1 and CTAG2), those involved in innate immune response (e.g., RIG-I/DDX58), and tumor suppressor functions (e.g., TYRP1). Genes whose expression is diminished by RARβ2 signalling include cell adhesion functions (e.g, CD164) nutritional or metabolic processes (e.g., FABP6), and the transcription factor, JUN.

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