Production of multiple cytokines by cultured human melanomas*

Abstract We screened a panel of 8 primary and 21 metastatic melanoma cell lines for constitutive secretion of cytokines. Melanomas expressed bioactivity for TGF-β (8/25 lines) and IFN (7/12), but not IL-2. Immu-noassays detected IL-1α (4/25), IL-1β (12/25), 1L-6 (13/29), IL-8 (29/ 29), TGF-β₂, (5/12) and GM-CSF (11 /29). but not IL-3, IL-4, TNF-α, or IFN-γ. There was no preferential association of cytokine production with cells cultured from primary versus metastatic disease, and only IL-8 was produced by all lines tested. These data demonstrate that cultured melanomas produce a variety of cytokines which are potentially capable of influencing tumor growth in vivo.     

Effects of low concentrations of cis- and trans-urocanic acid on cytokine elaboration by keratinocytes

The urocanic acid cis isomer (cis-UCA) is a possible cutaneous photoreceptor for the immunomodulatory phenomena that follow ultraviolet B irradiation. Several experiments in animals show an inhibitory action of cis-UCA on cellular immunity. However, the action of cis-UCA on the synthesis of cytokines in keratinocytes remains unknown. Long-term cultures of normal human keratinocytes were prepared in a serum-free medium, and stimulated with 1 μg/ml of phorbol 12-myristate 13-acetate (TPA) and UCA or UVB-UCA (10–100 μg/ml). Synthesis of the following cytokines was measured using ELISA and Northern blot techniques: TNF-α, IL-1α, IL-1β, IL-6, IL-8 and TGF-β1. TPA increased TNF-α protein levels in culture supernatants. No changes in IL-1α and IL-1β protein levels were detected in basal culture supernatant after TPA stimulus. TPA augmented RNA expression for TNF-α, IL-1α, IL-1β and TGF-β1. UCA isomers did not induce cytokine changes in protein synthesis. Expression of IL-1α and IL-1β genes was increased after exposure to 100 μg/ml UVB-UCA (70 μg/ml cis-UCA). A slight increase in TNF-α RNA expression was detected when the dose of UVB-UCA reached 100 μg/ml. No effects on cytokine synthesis were found after UCA stimulus. These results suggest that low doses of cis-UCA do not effect cytokine synthesis by keratinocytes.     

TGF-β1对人工皮肤光损伤炎症因子IL-1α、IL-6、TNF-α影响的研究

目的探讨TGF-β1对人工皮肤光损伤中炎症因子IL-1α、IL-6、TNF—α的影响。方法将角质形成细胞和成纤维细胞接种到胶原支架中体外构建人工皮肤,将人工皮肤分为四个实验组,即阴性对照组,紫外线照射,TGF-β1干预组,以及TGF—β1干预后再进行UV照射,采用ELISA法检测各实验组上清液中炎症因子IL-1α、IL-6、TNF—α．的浓度变化。结果体外培养的人工皮肤分为表皮和真皮层,与正常皮肤结构相似。与阴性对照组相比,UV照射组炎症因子IL-1仪、IL-6、TNF—α明显增加,有显著性差异（p〈0．01）;TGF-β1对IL-1α、IL-6、TNF-α的浓度没有明显影响（P〉0．05）;但是TGF—β1干预的uV组跟UV照射组比较则是IL—1α、IL-6、TNF-α浓度增加减少（p〈0．01）。结论TGF-β1对紫外线所致的人工皮肤光损伤的炎症因子IL-1α、IL-6、TNF-α产生有一定抑制作用,即对光损伤模型有保护作用。     

Normal response to tumor necrosis factor-alpha and transforming growth factor-beta by keratinocytes in psoriasis

Abstract Normal and chronic plaque psoriatic keralinocyte cultures were tested for their in vitro response to 2–200 ng/nil TNF-α and 0.1–10 ng/ml TGF-β in a serum-free culture system. All normal and lesional psoriatic epidermal cell cultures showed a dose- and lime-dependent inhibition of growth in response to TNF-α and TGF-β. Inhibition in individual cultures was first seen at a concentration of 2 ng/ml for TNF-α and 0.1 ng/ml for TGF-β at day 2, but became significant at 20 ng/ml and 1 ng/ ml for TNF-α and TGF-β respectively at days 2-6. This effect was statistically significant at days 3–4 for the group of normal (TNF-α and TGF-β, n = 10, p<0.01 and psoriatic cultures (TNF-α. n = 9, p<0.0l; TGF-β, n = 7, p<0.05). Epidermal cells from normal and psoriatic skin were inhibited to the same extent at the same optimal concentrations by each cytokine. Inhibition was abolished by the addition of specific antibody to each cytokine, whilst antibody to a different cytokine had no effect. Nuclear and/or nuclear membrane staining was observed with antibody to the p55 TNF receptor both in cultured keralinocyles and in the tipper epidermal layers of both normal and psoriatic skin. In contrast, plasma membrane and cytoplasmic expression of the p55 TNF receptor was observed on macrophages and lymphocytes infiltrating psoriatic der-mis. This study has shown that the growth of normal and psoriatic keratinocytes was equally inhibited by TNF-α and TGF-βin vitro. The expression of TNF receptor by psoriatic keratinocytes in vivo may permit regulation of epidermal growth by administration of TNF-α in this disease.     

颅内接种热灭活隐球菌对小鼠隐球菌脑膜脑炎作用的研究

目的 研究脑内接种热灭活的隐球菌(H-CN)在中枢神经系统隐球菌感染中的作用及对小鼠脑和脾白介素-1β(IL-1β)、干扰素γ(IFN-γ)和肿瘤坏死因子α(TNF-α)基因表达的影响。方法 建立脑内接种隐球菌造成中枢神经系统感染的小鼠模型,分实验组(给予2次脑内接种H-CN)、对照组(给予2次脑内接种生理盐水),分别取2组小鼠的脑和脾用RT-PCR方法检测IL-1β、IFN-γ及TNF-α的mRNA表达,然后给予2组小鼠脑内接种致死量的隐球菌,观察2组小鼠的生存时间及脑组织中菌落形成单位的变化。结果 实验组与对照组相比小鼠生存时间显著延长,小鼠脑组织中隐球菌菌落形成单位明显减少。小鼠脑组织总RNA以IL-1β、IFN-γ、TNF-α引物进行的RT-PCR产物,实验组IL-1β表达阳性,IFN-γ、TNF-α均表达阴性;对照组IL-1β、IFN-γ、TNF-α均表达阴性。小鼠脾组织总RNA以IL-1β、IFN-γ、TNF-α引物进行的RT-PCR产物2组均表达阳性,差异无显著性。结论 给予小鼠脑内接种H-CN可提高中枢神经系统对隐球菌感染的抵抗力,中枢神经系统抗隐球菌机制很可能与H-CN引起局部细胞因子IL-1β的分泌有关。     

Barrier disruption increases gene expression of cytokines and the 55 kD TNF receptor in murine skin

Abstract The signalling mechanisms that regulate epidermal permeability barrier homeostasis arc not known. Previous Northern blot analysis showed that both acute and chronic barrier disruption increase mRNA levels of several cytokines in murine epidermis. To further characterize the epidermal response to barrier abrogation, we used more sensitive, multi-probe RNasc protection assays to measure the mRNA levels of additional cytokines. as well as cytokine receptors in acute and chronic models of barrier disruption. Normal mouse epidermis expressed interleukin (IL)-lα, interferon-γ (IFN-γ). tumor necrosis factor-α (TNF-α) and IL-6 mRNAs. Following tape-stripping, only the mRNA levels for TNF-α, IL-lα, IL-lβ and IL-6 increased at 2.5 and 7 h, and returned toward normal levels by IX h. No mRNAs encoding TNF-β. IL-2, IL-3. IL-4 or IL-5, were detected in the epidermis either under basal conditions or after tape-stripping. Similarly, in a chronic model, essential fatty acid deficiency, epidermal levels of TNF-α, IL-lα, IL-lβ and IL-6 mRNAs, but not IFN-γ mRNA. were elevated over controls; and again, mRNAs for the remaining probed cytokines were not detected. In contrast, in the dermis. only IL-Iβ mRNA levels increased 2.5 h after tape-stripping, and remained elevated at I8 h. mRNAs encoding the IL-1 (p60), IFN-γ ami IL-6 receptors were present in epidermis, but their levels remained unchanged following either acute or chronic barrier disruption. In contrast, epidermal TNF (p55) receptor mRNA levels were increased by 87% (P<0.01) at 2.5 h, returned to control levels at 7 h and were increased by 68% (p<0.03) at 18 h after tape-stripping. The increase at 2 h was confirmed by Northern blot analysis and was not prevented by latex occlusion performed immediately after tape-stripping. mRNAs for the IL-I (p80) receptor and TNF (p75) receptor were not detected in epidermis. Low levels of TNF (p55) receptor mRNA were present in the dermis. and they remained unchanged after tape-stripping. The presence of specific receptor mRNAs in the epidermis and dermis suggests that these tissues are capable of responding in an autocrine and/or paracrine fashion to the cognate cytokines. These results suggest that epidermal cytokines produced after barrier disruption may initiate a cytokine cascade which could regulate cytokine and cytokine receptor production and/or inflammatory responses.     

Semaphorin 7A on keratinocytes induces interleukin-8 production by monocytes

Background

Semaphorin 7A (Sema7A) expressed on activated T cells stimulates cytokine production in monocytes through its receptor, α1β1 integrin.

Objective

To study the significance of Sema7A expressed on keratinocytes in skin inflammation where interaction between keratinocytes and β1-integrin expressing inflammatory cells, such as monocytes, takes place.

Methods

The regulation of Sema7A expression on keratinocytes by various cytokines was studied by flow cytometry and immunoblot. β1-integrin expressing human monocyte cell line, THP-1 cells, were co-cultured with paraformaldehyde-fixed normal human epidermal keratinocytes (NHK) and IL-8 production by THP-1 cells was studied. The significance of β1-integrin or Sema7A within this cell interaction was examined by the experiments using β1-integrin blocking antibody or Sema7A siRNA.

Results

IFN-γ and TNF-α slightly increased Sema7A expression, while IL-4 decreased it. Among cytokines tested, TGF-β1 most strikingly increased the Sema7A expression on NHK. When NHK was stimulated by TGF-β1, paraformaldehyde-fixed, and co-cultured with THP-1 cells, IL-8 production by THP-1 cells was increased compared to THP-1 cells only. When THP-1 cells were pretreated with β1-integrin blocking antibody, this increase in IL-8 production by THP-1 cells was inhibited. Likewise, when NHK were pretreated with Sema7A siRNA before fixation and co-cultured with THP-1 cells, increase in IL-8 production by THP-1 cells was inhibited.

Conclusion

Our results suggest that Sema7A on keratinocytes and β1-integrin on monocytes contribute to monocyte activation by keratinocytes within skin inflammation, such as psoriasis or wound.     

Expression of Foxp3, TGF-β and IL-10 in American cutaneous leishmaniasis lesions

Regulatory T cells (Tregs) are a unique population of CD25+CD4+ T cells that regulate innate and adaptive immune responses and have the ability to control the excessive or misdirected effects of the immune system. This modulation involves different mechanisms, such as the suppression of T cell proliferation and cytokine production, the secretion of suppressive cytokines (IL-10 and TGF-β) and the induction of effector T cell apoptosis in humans with infectious diseases such as Leishmania infections. The aim of this study was to evaluate the expression of Foxp3, IL-10 and TGF-β through immunohistochemistry in 22 skin biopsies of patients with localized cutaneous leishmaniasis (LCL) caused by Leishmania (Viannia) spp. from an endemic area in pre-Amazonian area of Maranhão State, Brazil. The density of these markers was also analyzed according to the species of parasite and the progression of the disease. The cellular density was 234 cells/mm² for Foxp3+ cells, 357 cells/mm² for TGF-β+ cells and 648 cells/mm² for IL-10+ cells in the studied skin lesions. The analysis of the cellular density of these immunological markers in relation to the species of Leishmania demonstrated that lesions caused by L. (V.) braziliensis had a lower density of Foxp3+ cells than lesions caused by L. (Viannia) spp. The expression of IL-10 was also lower in lesions caused by L. (V.) braziliensis. There were no significant differences in TGF-β expression between the two groups. The evaluation of these markers according to the progression of the disease did not reveal any significant differences. These findings suggest that Treg Foxp3+ cells, IL-10, and TGF-β play important roles in the immunopathogenesis of LCL and that these roles differ depending on the causal Leishmania species.     

Inter-regulation of Th17 cytokines and the IL-36 cytokines in vitro and in vivo: implications in psoriasis pathogenesis

Accumulating evidence indicates that IL-1 family members and Th17 cytokines have a pathogenic role in psoriasis. We investigated the regulatory interactions of the IL-1-like IL-36 cytokine family and the Th17 cytokines in the context of skin inflammation. We observed increased gene expression of all three IL-36 cytokines in a Th17-dominant psoriasis-like animal model. The induction was downregulated by neutralizing IL-22. Expression of the IL-36s was also induced in cultured primary human keratinocytes (KC) by IL-17A and tumor necrosis factor (TNF)-α, and IL-22 synergized with IL-17A and TNF-α. Furthermore, the IL-36s directly induced their own expression and the production of proinflammatory mediators (TNF-α, IL-6, IL-8) in KC. These functions were markedly enhanced with the addition of IL-17A or TNF-α to the cultures. Similarly, IL-36α and IL-36β augmented IL-17A-mediated induction of antibacterial peptides. Finally, we show that the increased gene expression of IL-36 correlated with Th17 cytokines in the lesions of psoriatic patients. Our results indicate that the IL-36 cytokines are not only regulated by Th17 cytokines, but that they themselves can regulate the expression and enhance the function of Th17 cytokines. We propose that a feedback loop between the IL-36 and Th17 cytokines is involved in driving cytokine expression in psoriatic tissues.     

RANTES expression in psoriatic skin, and regulation of RANTES and IL-8 production in cultured epidermal keratinocytes by active vitamin D3 (tacalcitol)

The chemokine RANTES is a chemoattractant for eosinophils, T lymphocytes of memory phenotype and monocytes, suggesting that it plays an important part in chronic inflammatory and allergic diseases. In various types of cells, RANTES production is markedly induced by tumour necrosis factor (TNF)-α and interferon (IFN)-γ in combination. Psoriasis vulgaris is a chronic cutaneous inflammatory disease. Cytokines and chemokines produced by T cells and epidermal keratinocytes, such as interleukin (IL) 8, are involved in the pathogenesis of psoriasis. T-cell clones obtained from psoriatic skin have been shown to produce the Th1 cytokine IFN-γ. In addition, abnormal expression of proinflammatory cytokines including TNF-α has been observed in psoriatic lesions. These reports led us to hypothesis that psoriatic skin could provide epidermal keratinocytes with TNF-α and IFN-γ, so that keratinocytes could produce RANTES. In this study, we addressed the question as to whether RANTES was involved in psoriasis vulgaris. Immunohistochemistry of skin biopsies showed RANTES was present in the intercellular spaces between epidermal keratinocytes, in the fully developed lesions from the middle to the edge of psoriatic plaques, but not in the perilesional uninvolved and healthy control skin. Further, we confirmed the production of RANTES, together with IL-8, by cultured normal human epidermal keratinocytes, using an enzyme-linked immunosorbent assay. Stimulation with TNF-α and IFN-γ in combination synergistically increased the RANTES production in this system. These results clearly demonstrate the expression of RANTES in psoriatic lesions and suggest the involvement of this chemokine in the outcome of cutaneous inflammatory diseases. Tacalcitol (1α,24(R)-dihydroxyvitamin D₃), an active vitamin D₃ analogue, inhibited RANTES and IL-8 production in cultured normal epidermal keratinocytes. This result indicates that active vitamin D₃ is effective in the regulation of chemokine production by epidermal keratinocytes, which may partly account for its action as an antipsoriatic drug.     

Cytokine and chemokine ligand expression in cutaneous lupus erythematosus

There is increasing evidence that cytokines as well as chemokines are important players in the pathogenesis of lupus erythematosus (LE). We aimed to compare cytokine and chemokine profiles in different types of cutaneous LE. We investigated lesional mRNA and protein expression of various cytokines and chemokines in patients with chronic discoid LE (CDLE, n=15), subacute cutaneous LE (SCLE, n=11), and lupus erythematosus tumidus (LET, n=21). TNF-α, INF-γ, TGF-β, IL-6, IL-10, IL-12p40, CXCL9, and CXCL10 mRNA expression were significantly increased in SCLE when compared to CDLE. Moreover, LET also showed significantly increased mRNA expression of TNF-α, TGF-β, IL-10, IL-12p40 and CXCL9, as compared to CDLE. In all LE subtypes, CXCL9 and CXCL10 mRNA expression significantly correlated with INF-γ mRNA expression, as indicated by r-values ranging from 0.71 - 0.87. Immunohistochemistry for TNF-α, INF-γ, and IL-10 gave support to our RT-PCR results. In conclusion, our results suggest that T helper 1, as well as T helper 2 cytokines are differentially expressed in CDLE, SCLE, and LET. Compared to CDLE, the highest cytokine and chemokine ligand profiles are found in SCLE followed by LET. Our correlation studies also support the importance of an IFN-driven inflammation in cutaneous LE.     

TNF-α和IL-1β对HaCaT细胞诱生型一氧化氮合酶表达的影响

目的　探讨炎症性细胞因子肿瘤坏死因子 α(tumornecrosisfactor α ,TNF α)协同白细胞介素 1β(inter leukin 1β ,IL 1β)对体外培养角质形成细胞 (keratinocye ,KC)株HaCaT细胞诱生型一氧化氮合酶 (induciblenitricoxidesyn thase ,iNOS)mRNA和蛋白表达的调节作用 ,以及地塞米松对TNF α和IL 1β作用的影响。 方法　用RT PCR、Westernblotting和免疫组织化学 (SP)方法检测HaCaT细胞iNOSmRNA和蛋白表达情况。结果　正常培养HaCaT细胞iNOS微弱表达或不表达 ,TNF α协同IL 1β显著上调HaCaT细胞iNOSmRNA和蛋白表达 ,地塞米松可显著抑制TNF α和IL 1β的作用。结论　推测TNF α和IL 1β可能通过上调角质形成细胞表达iNOS合成释放的一氧化氮 (niricoxide ,NO)参与皮肤免疫和炎症反应 ;地塞米松的治疗效应可能部分与其能抑制iNOS表达有关。     

Podoplanin expression in wound and hyperproliferative psoriatic epidermis: regulation by TGF-β and STAT-3 activating cytokines, IFN-γ, IL-6, and IL-22

Background

Podoplanin (PDPN)/T1α/aggrus/PA2.26 antigen, a transmembranous glycoprotein, is a well-known lymphatic endothelial marker. Recent evidence indicates that PDPN is also expressed in keratinocytes especially of sebaceous glands.

Objective

To verify expression-pattern and the regulatory mechanism of PDPN in human epidermal keratinocytes.

Methods

PDPN-expression pattern was analyzed in normal and psoriatic epidermis by immunostaining. The regulatory mechanism of PDPN-expression of keratinocytes by cytokines was analyzed using specific inhibitors, siRNA, and adenoviral shRNA of signaling pathways.

Results

In normal skin, PDPN was expressed on the basal cell layer of sebaceous glands and on the outer root sheath of hair follicles. While no expression was detected in the normal interfollicular epidermis, PDPN was detected in the basal cell layer of wound and hyperproliferative psoriatic epidermis, where the granular layer is lacking. TGF-β1 and IFN-γ independently upregulated PDPN-expression of keratinocytes via TGF-β receptor-Smad pathway and JAK-STAT pathway, respectively. IL-6 and IL-22 also stimulated PDPN-expression of keratinocytes accompanied by STAT-3 phosphorylation. siRNA of STAT-1, inhibitors of STAT-3 signaling, AG490, STAT-3 inhibitor VI, and si/shRNA of STAT-3 inhibited the PDPN-expression of keratinocytes induced by IFN-γ, IL-6 and IL-22 but not by TGF-β1.

Conclusion

These results indicate that TGF-β1, IFN-γ, IL-6, and IL-22 induce PDPN-expression of keratinocytes, which might be significantly involved in the wound healing process as well as in the pathomechanism of hyperproliferative psoriatic epidermis.     

苯并芘与肽聚糖体外协同对人皮脂腺细胞炎症因子表达的影响

目的：检测苯并芘（Bap）和革兰氏阳性菌细菌壁肽聚糖（PGN)体外对SZ95人皮脂腺细胞炎症因子表达的影响。方法：体外培养SZ95永生化人皮脂腺细胞,分为空白对照组、Bap组、PGN组和（Bap+PGN）组, PGN浓度为20μg/mL,Bap浓度 为10-5mol/L。 RT-PCR和ELISA检测SZ95永生化人皮脂腺细胞分泌白介素(IL-1α、IL-1β）、TNF-α mRNA和蛋白表达水平。结果：（Bap+PGN）组IL-1α,IL-1β和TNF-αmRNA及蛋白表达水平高于空白对照组、Bap组和PGN组,差异具有统计学意义（P<0.01）。结论：苯并芘协同增强PGN诱导的皮脂腺细胞炎症因子IL-1α,IL-1β,TNF-α的表达,这可解释为什么环境污染可加重或诱导痤疮 的发生。     

Epidermal stratification reduces the effects of UVB (but not UVA) on keratinocyte cytokine production and cytotoxicity

Ultraviolet (UV) radiation induces cytokine release from cultured keratinocytes as well as from epidermis in vivo. The purpose of this study was to determine whether differentiation of cultured keratinocytes into stratified epithelium decreases the effects of UVA and UVB radiation on cytokine release. Interleukin-1 (IL-1)α, IL-1β and tumor necrosis factor (TNF)-α release from human keratinocytes and reconstituted human epidermis was measured after exposure to UVA or UVB radiation. Release of IL-1α, IL-1β, and TNF-α was induced by both UVA and UVB radiation from both keratinocytes and reconstituted epidermis. Release of these cytokines was correlated with cytotoxicity. Keratinocyte cultures were far more sensitive to UVB radiation than reconstituted epidermis, in terms of both cytotoxicity and cytokine release. In contrast, epidermal stratification/differentiation had much less effect on the sensitivity to UVA radiation. We conclude that epidermal stratification and the formation of a stratum corneum provide protection against UVB radiation but have limited barrier effect against UVA radiation.     

Sweet’s syndrome: Is the pathogenesis mediated by helper T cell type 1 cytokines?

Background: The pathogenesis of Sweet’s syndrome (acute febrile neutrophilic dermatosis; SS) is still not fully understood. An imbalance between helper T cell types 1 and 2 cytokine secretion patterns has been shown to be relevant in many diseases. Objective: We assessed the serum cytokine levels (interleukin [IL]-1α, IL-1β, IL-2, interferon gamma [IFN-γ], IL-4) in patients with SS. Methods: Eight patients with SS were analyzed for their clinical features and serum cytokine levels and compared with normal control subjects. Results: In patients serum levels of IL-1α, IL-1β, IL-2, and IFN-γ were significantly elevated, whereas the IL-4 level was within the normal range. Conclusion: Our findings suggest that the pathogenesis of SS is probably mediated through helper T cell type 1 cytokines (IL-2, IFN-γ) rather than helper T cell type 2 cytokines (IL-4). (J Am Acad Dermatol 1998;39:940-3.)     

In situ analysis of transforming growth factors-β(TGF-β1, TGG-β2, TGF-β3) and TGF–β type II receptor expression in basal cell carcinomas

Transforming growth factor-beta (TGF-β) consists of a highly homologous family of multifunctional peptides which are differentially expressed and function in a wide range of target cells. Aberrant expressions of TGFβs have been implicated in a number of disease processes, particularly those involving fibrotic and inflammatory lesions, and loss of TGF-β growth inhibition may play a part in the progression of certain neoplasms. In the present study, we have analysed and compared, by in situ hybridization, mRNA expression of transforming growth factors-β(TGF-β1, TGF-β2. TGF-β3) and TGF-β type II receptor (TβR II). and. by immunohistochemistry, the distribution of TGF-β3 protein in normal human skin and in basal cell carcinoma (BCC). The stroma of most BCCs revealed enhanced TGF-β1 and TβR II mRNA expression when compared with normal dermis. A minority of BCCs also showed stromal overexpression of TGF-β2 and/or TGF-β3 mRNA. However, tumour tissues of all BCCs revealed weaker TGF-β3 mRNA and protein expression than normal interfollicular epidermis and hair follicle epithelia, whereas expression of TGF-β1 mRNA was comparably weak in tumour tissues and normal skin epithelia. Expression of TGF-β2 mRNA, which was clearly detectable in distinct hair follicle epithelia, was only barely detectable in normal interfollicular epidermis and in tumour tissues. In contrast, abundant TβR II mRNA expression was observed both in normal skin epithelia and tumour tissues. From these findings, we suggest that increased stromal TGF-β activity induces fibrotic alterations which promote tumour survival and/or progression via paracrine mechanisms, whereas lack of TGF-β expression by tumour cells may contribute to an autocrine growth control defect in BCCs.