SUMMARYSkin and hair follicle morphogenesis and homeostasis require the integration of multiple signaling pathways, including Hedgehog (Hh) and Wingless (Wnt), and oriented cell divisions, all of which have been associated with primary cilia. Although studies have shown that disrupting dermal cilia causes follicular arrest and attenuated Hh signaling, little is known about the role of epidermal cilia. Here, epidermal cilia function was analyzed using conditional alleles of the ciliogenic genes Ift88 and Kif3a. At birth, epidermal cilia mutants appeared normal, but developed basaloid hyperplasia and ingrowths into the dermis of the ventrum with age. In addition, follicles in the tail were disorganized and had excess sebaceous gland lobules. Epidermal cilia mutants displayed fewer long-term label-retaining cells, suggesting altered stem cell homeostasis. Abnormal proliferation and differentiation were evident from lineage-tracing studies and showed an expansion of follicular cells into the interfollicular epidermis, as is seen during wound repair. These phenotypes were not associated with changes in canonical Wnt activity or oriented cell division. However, nuclear accumulation of the DNp63 transcription factor, which is involved in stratification, keratinocyte differentiation and wound repair, was increased, whereas the Hh pathway was repressed. Intriguingly, the phenotypes were not typical of those associated with loss of Hh signaling but exhibited similarities with those of mice in which DNp63 is overexpressed in the epidermis. Collectively, these data indicate that epidermal primary cilia may function in stress responses and epidermal homeostasis involving pathways other than those typically associated with primary cilia.
Cyclosporine A (CsA) is an immunosuppressive drug commonly used for maintaining chronic immune suppression in organ transplant recipients. It is known that patients receiving CsA manifest increased growth of aggressive nonmelanoma skin cancers. However, the underlying mechanism by which CsA augments tumor growth is not fully understood. Here, we show that CsA augments the growth of A431 epidermoid carcinoma xenograft tumors by activating tumor growth factor β-activated kinase1 (TAK1). The activation of TAK1 by CsA occurs at multiple levels by kinases ZMP, AMPK and IRAK. TAK1 forms heterodimeric complexes with TAK binding protein 1 and 2 (TAB1/TAB2) which in term activate nuclear factor κB (NFκB) and p38 MAP kinase. Transcriptional activation of NFκB is evidenced by IKKβ-mediated phosphorylation-dependent degradation of IκB and consequent nuclear translocation of p65. This also leads to enhancement in the expression of its transcriptional target genes cyclin D1, Bcl2 and COX-2. Similarly, activation of p38 leads to enhanced inflammation-related signaling shown by increased phosphorylation of MAPKAPK2 and which in turn phosphorylates its substrate HSP27. Activation of both NFκB and p38 MAP kinase provide mitogenic stimuli to augment the growth of SCCs.
A variety of studies were performed with naproxen (a standard NSAID with a good cardiovascular profile), sulindac, and their nitric oxide (NO)-derivatives. In Fisher 344 rats, OH-BBN (2x/week for 8 weeks by gavage) induced invasive urinary bladder cancers. When treatment was initiated one week following the final dose of OH-BBN, both naproxen (400 ppm) and sulindac (400 ppm) were highly effective preventive agents at these human equivalent doses. The NO-derivatives of each compound (NO-naproxen, 550 ppm and NO-sulindac, 520 ppm) were similarly effective. When the dose of naproxen was decreased from 400 ppm to 75 ppm a strong preventive effect was still observed. This activity was observed even when treatment with naproxen was started 12 weeks after the last OH-BBN treatment; microcarcinomas already existed at this time. In an attempt to make a more direct comparison between the human and rat data, animals were treated with 40 mg/kg BW/day of naproxen by gavage. Similar to the dietary dose of 400 ppm, the agent was highly effective; however, gavaging the rats permitted more direct comparison of the pharmacokinetics observed in the rat with known results in humans. In contrast to the naproxen data, reducing the dose of sulindac from 400 to 150 ppm, a dose comparable to the human dose employed by Meyskens, et al. (Cancer Prevention Res. 1:32-38, 2008), resulted in only limited activity. Finally, the effects of naproxen and NO-naproxen on modulation of gene expression in the livers of treated rats were determined. Limited, but similar, gene expression changes induced by both agents were observed. Interestingly, neither agent induced the antioxidant response element genes [e.g., GST Pi, quinone oxidoreductase, aldo keto reductase A37 (aflatoxicol)] that one might have expected to be highly induced by free NO. Supported by the NCI contract number HHSN261200433001C. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1849. doi:10.1158/1538-7445.AM2011-1849
Cutaneous T-cell lymphoma (CTCL) designates a heterogeneous group of malignancies, characterized by the infiltration and detection of transformed T-cell lymphocytes in the skin. Although there is no cure for CTCL, a wide range of treatment options have been developed for use in the clinical setting. Bexarotene, a retinoid X receptor (RXR) agonist or rexinoid, is a commonly used treatment modality for CTCL. However, documented increases in the levels of triglycerides of CTCL patients, resulting from treatment with bexarotene, point to concerns over the long-term use and efficacy of this anticancer agent. We have recently synthesized a novel rexinoid, 9-cis UAB30, which does not elevate triglycerides in vivo and have begun evaluating its use as a potential chemotherapeutic agent for the treatment of CTCL. In this study, we compared the efficacy of 9-cis UAB30 to that of bexarotene in reducing cell proliferation and inducing apoptosis, in the three human CTCL cell lines HH, MJ, and Hut78. A standard XTT assay was used to determine the rate of cell proliferation of CTCL cells. In all three lines, 9-cis UAB30 was equally and sometimes more effective than bexarotene at suppressing cell proliferation. Using an annexin V binding assay, we next analyzed the rate of apoptosis in these human CTCL lines. Interestingly, we observed the MJ cell line to be resistant to apoptosis, when treated with either compound. The HH cell line exhibited a similar increase in apoptosis, whether treated with 9-cis UAB30 or bexarotene. Finally, the Hut78 cell line showed a greater sensitivity to apoptosis, when treated with 9-cis UAB30 as compared to bexarotene. Taken together, these preliminary results indicate that 9-cis UAB30 appears to be equally if not more effective than bexarotene at suppressing cell proliferation and appears to exert differential effects on the rate of apoptosis that may be cell-line specific. These differential responses of human CTCL cells have implications for the development of next-generation, rexinoid-based therapies and reveal that 9-cis UAB30 may be a better alternative for the treatment of CTCL. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the Second AACR International Conference on Frontiers in Basic Cancer Research; 2011 Sep 14-18; San Francisco, CA. Philadelphia (PA): AACR; Cancer Res 2011;71(18 Suppl):Abstract nr A20.
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