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Epithelial-to-mesenchymal transition (EMT) is critical for embryonic development and wound healing, and occurs in fibrotic disease and carcinoma. Here, we show that EMT also occurs within the bulge, the epithelial stem cell (eSC) niche of human scalp hair follicles, during the inflammatory permanent alopecia, lichen planopilaris. We show that a molecular EMT signature can be experimentally induced in healthy human eSCs in situ by antagonizing E-cadherin, combined with transforming growth factor-β1, epidermal growth factor, and IFN-γ administration, which to our knowledge has not been reported previously. Moreover, induction of EMT within primary human eSCs can be prevented and even partially reversed ex vivo by peroxisome proliferator-activated receptor-γ agonists, likely through suppression of the transforming growth factor-β signaling pathway. Furthermore, we show that peroxisome proliferator-activated receptor-γ agonists also attenuates the EMT signature even in lesional lichen planopilaris hair follicles ex vivo. We introduce lichen planopilaris as a model disease for pathological EMT in human adult eSCs, report a preclinical assay for therapeutically manipulating eSC EMT within a healthy human (mini-)organ, and show that peroxisome proliferator-activated receptor-γ agonists are promising agents for suppressing and partially reversing EMT in human hair follicles eSCs ex vivo, including in lichen planopilaris.

For many years, extracellular matrix (ECM) was considered to function as a tissue support and filler. However, we now know that ECM proteins control many cellular events through their interaction with cell-surface receptors and cytoplasmic signaling pathways. For example, they regulate cell proliferation, cell division, cell adhesion, cell migration, and apoptosis. We focus in this review on a laminin isoform, laminin-332 (formerly termed laminin-5), a major component of the basement membrane (BM) of skin and other epithelial tissues. It is composed of 3 subunits (α3, β3, and γ2) and interacts with at least two integrin receptors expressed by epithelial cells (α3β1 and α6β4 integrin). Mutations in either laminin-332 or integrin α6β4 result in junctional epidermolysis bullosa, a blistering skin disease, while targeting of laminin-332 by autoantibodies in cicatricial pemphigoid leads to dysadhesion of epithelial cells from their underlying connective tissue. Abnormal expression of laminin-332 and its integrin receptors is also a hallmark of certain tumor types and is believed to promote invasion of colon, breast and skin cancer cells. Moreover, there is emerging evidence that laminin-332 and its protease degradation products are not only found at the leading front of several tumors but also likely induce and/or promote tumor cell migration. Thus, in this review, we focus specifically on the role of laminin-332 and its integrin receptors in adhesion, proliferation, and migration/invasion of cancer cells. Finally, we discuss strategies for the development of laminin-332-based antagonists for the treatment of malignant tumors.

No abstract

Cyclooxygenase 2 (COX-2) has been suggested to be associated with liver carcinogenesis. Several reports have shown that NSAIDs inhibit the growth of hepatocellular carcinoma cell lines. There is little evidence of how COX-2 inhibitors regulate the proliferation of hepatocellular carcinoma cells or the mechanism involved. In our study, we investigated the growth-inhibitory mechanism of a selective COX-2 inhibitor, NS-398, in 4 hepatocellular carcinoma cell lines by studying cell growth, COX-2 and proliferating cell nuclear antigen (PCNA) expression, cell cycle distribution and the evidence of apoptosis. NS-398 inhibited the growth of all 4 cell lines in a time-and dose-dependent manner and the inhibitory effects were independent of the level of COX-2 protein expression. PCNA expression was downregulated by NS-398 in a dose-independent manner. NS-398 caused cell cycle arrest in the S phase with a reduction in cell numbers and cell accumulation in the G0/G1 phase, for all 4 cell lines. No evidence of apoptosis was observed in our present study. Key words: selective COX-2 inhibitor; cell growth; cell cycle; hepatocellular carcinoma cellsCyclooxygenases (COX) are key rate-limiting enzymes involved in the conversion of arachidonic acid to prostaglandin H2, the precursor of various compounds including prostaglandins (PGs), prostacyclin and thromboxanes. There are at least 2 isoforms of COX: COX-1 and COX-2. COX-1 is expressed constitutively in a wide variety of tissues whereas COX-2 is highly inducible and is expressed in response to a variety of proinflammatory agents and cytokines. 1,2 Overexpression of COX-2 has been demonstrated in various tumor tissues such as colon cancer, pancreatic cancer and hepatocellular carcinoma. [3][4][5][6][7] Although several studies have shown the upregulation of COX-2 in cirrhotic tissues adjacent to hepatocellular carcinoma (HCC) and welldifferentiated HCC, the precise role of COX-2 in carcinogenesis remains unclear. 7,8 A few reports have shown that NSAIDs inhibited the growth of various cancer cell lines including those derived from hepatocellular carcinoma. 9 -11 The question arises whether COX-2 also is a target for the prevention or treatment of hepatocellular carcinoma, as it is for colon cancer. 12 There is little evidence, however, of how COX-2 inhibitors regulate the proliferation of hepatocellular carcinoma cells or the mechanism involved. In our study, we investigated the growth-inhibitory mechanism of a selective COX-2 inhibitor, NS-398, in hepatocellular carcinoma cell lines. MATERIAL AND METHODS Cell lines and cell cultureFour human hepatocellular carcinoma cell lines, PLC/PRF5, HepG2, Mahlavu and HuH-7, were obtained from the American Type Culture Collection. Cells (2 ϫ 10 5 cells) were grown for 24 hr in DMEM (PLC/PRF5 and HepG2) (ICN; Biomedicals Inc., Aurora, MI), minimum essential Eagle's medium (Mahlavu) (ICN) and RPMI 1640 (HuH-7) (ICN) supplemented with 10% FBS at 37°C under 5% CO 2 /95% air in 100 mm 2 cell culture dishes. Then, NS-398 (Cayman Chemical, Ann Ar...