Efficacy of the EGFr inhibitor Iressa on development of chemically-induced urinary bladder cancers: dose dependency and modulation of biomarkers.

The effects of the EGFr inhibitor Iressa on development of urinary bladder cancers induced by hydroxybutyl(butyl)nitrosamine (OH-BBN) in rats were examined. Iressa treatment (4.5 or 1.5 mg/kg BW/day) beginning one week after the last dose of OH-BBN decreased the occurrence of large (>200 mg) bladder cancers at termination of the study by 75 and 52%, respectively. Treatment with Iressa (10 mg/kg BW/day) beginning one week or three months (delayed initiation) after the last dose of OH-BBN also significantly increased tumor latency and decreased the incidence of palpable bladder cancers. In the delayed initiation study, microscopic cancers already existed when treatment was initiated; implying that the effects of Iressa occur late in tumor progression. Potential pharmacodynamics and/or efficacy biomarkers modulated by short-term exposure (5 day) to Iressa (10 mg/kg BW/day) were determined in palpable bladder lesions by using three different approaches: i) direct immunohistochemical examination of EGFr related proteins; which showed that phosphorylated EGFr, AKT and ERK were significantly decreased; ii) measurement of protein expression by two dimensional gel electrophoresis and tandem mass spectrometry. This showed that the Annexin A2, MAP kinase kinase and nucleolin (all proteins associated with the VEGF pathway) were decreased in treated tumors; and iii) measurement of gene expression determined in gene microarrays demonstrated that numerous pathways were markedly altered by Iressa treatment. In particular, cell cycle genes related to the anaphase protein complex (APC) pathway, including CDC 20, cyclin B1, BUB1 and both of the Aurora kinases, were significantly decreased.

Role of epidermal primary cilia in the homeostasis of skin and hair follicles.

Skin 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 ΔNp63 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 ΔNp63 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.

Procarcinogenic effects of cyclosporine A are mediated through the activation of TAK1/TAB1 signaling pathway.

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 non-melanoma 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 ß-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 IKKß-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.