Inhibition of erbB receptor family members protects HaCaT keratinocytes from ultraviolet-B-induced apoptosis

Evaluation of bcl-2, bax and c-erbB-2 Levels in Chronic Otitis Patients with or without Cholesteatoma

Objective

The aim of this study was to evaluate bcl-2, bax, and c-erbB-2 expressions in primary and secondary acquired cholesteatoma and to indicate the role of apoptosis and accompanying increased cellular proliferation in the pathogenesis of cholesteatoma.

Methods

Samples obtained from the skin of the external ear canal (EEC) of patients operated for chronic otitis media (COM) without cholesteatoma constituted Group 1; samples from the EEC skin of patients in Group 3 operated for COM with cholesteatoma and from the EEC skin of patients in Group 4 constituted Group 2; samples obtained from the cholesteatoma matrix of patients operated for COM with primary acquired cholesteatoma constituted Group 3; and samples obtained from the cholesteatoma matrix of patients operated for COM with secondary acquired cholesteatoma constituted Group 4. The assessment of the positive cell ratio was based on the presence of the following findings and was semiquantitatively classified into four groups: 0, no staining; + cell staining (weak positive staining: 1%-33%); ++ cell staining (moderately positive staining: 34%-66%); and +++ cell staining (strong positive staining: 67%-100%).

Results

Comparison of the staining scores of bcl-2, bax, and c-erbB-2 revealed a statistically insignificant difference in the staining of samples obtained from the EEC skin (p>0.05). Decreased bcl-2 expression and increased bax and c-erbB-2 expressions were determined in primary and secondary acquired cholesteatoma epithelium compared with the EEC skin of patients operated for COM with or without cholesteatoma, and the differences were found to be statistically significant (p<0.05).

Conclusion

In acquired cholesteatoma epithelium, the finding of decreased bcl-2 expression as well as increased bax and c-erbB-2 expressions compared with the EEC skin is an indicator of the increase in both cellular proliferation and apoptosis.

Distinct epidermal keratinocytes respond to extremely low-frequency electromagnetic fields differently

Following an increase in the use of electric appliances that can generate 50 or 60 Hz electromagnetic fields, concerns have intensified regarding the biological effects of extremely low-frequency electromagnetic fields (ELF-EMFs) on human health. Previous epidemiological studies have suggested the carcinogenic potential of environmental exposure to ELF-EMFs, specifically at 50 or 60 Hz. However, the biological mechanism facilitating the effects of ELF-EMFs remains unclear. Cellular studies have yielded inconsistent results regarding the biological effects of ELF-EMFs. The inconsistent results might have been due to diverse cell types. In our previous study, we indicated that 1.5 mT, 60 Hz ELF-EMFs will cause G1 arrest through the activation of the ATM-Chk2-p21 pathway in human keratinocyte HaCaT cells. The aim of the current study was to investigate whether ELF-EMFs cause similar effects in a distinct epidermal keratinocyte, primary normal human epidermal keratinocytes (NHEK), by using the same ELF-EMF exposure system and experimental design. We observed that ELF-EMFs exerted no effects on cell growth, cell proliferation, cell cycle distribution, and the activation of ATM signaling pathway in NHEK cells. We demonstrated that the 2 epidermal keratinocytes responded to ELF-EMFs differently. To further validate this finding, we simultaneously exposed the NHEK and HaCaT cells to ELF-EMFs in the same incubator for 168 h and observed the cell growths. The simultaneous exposure of the two cell types results showed that the NHEK and HaCaT cells exhibited distinct responses to ELF-EMFs. Thus, we confirmed that the biological effects of ELF-EMFs in epidermal keratinocytes are cell type specific. Our findings may partially explain the inconsistent results of previous studies when comparing results across various experimental models.

Ado-trastuzumab emtansine-associated telangiectasias in metastatic breast cancer: a case series

Treatment of HER2-positive metastatic breast cancer with ado-trastuzumab emtansine (T-DM1), a novel antibody-drug conjugate, has resulted in both improved progression-free and overall survival. Recognition and treatment of diverse adverse events related to T-DM1 is critical for safety and tolerability. The most frequent adverse events with T-DM1 include fatigue, diarrhea, anemia, elevated transaminases, and mild-to-moderate hemorrhagic events, which are thought to be related to induced thrombocytopenia. Here, we present five case series of cutaneous and mucosal telangiectasias, definitely related to T-DM1. The development of telangiectasias represents a newly recognized adverse effect of T-DM1. We provide description and timing of the telangiectasias and review the mechanisms that may explain the formation of these vascular lesions in association with T-DM1. Further, we describe associated bleeding events and propose that induced telangiectasias could represent an additional cause of T-DM1-associated hemorrhage.

Low electric fields induce ligand-independent activation of EGF receptor and ERK via electrochemical elevation of H(+) and ROS concentrations

Physiological electric fields are involved in many biological processes and known to elicit their effects during long exposures ranging from a few hours to days. Following exposure to electric fields of physiological amplitude, epidermal growth factor receptor (EGFR) was demonstrated to be redistributed and upregulated with further intracellular signaling such as the MAPK signaling cascade. In our study we demonstrated EGFR activation and signaling induced by short train of pulsed low electric field (LEF) (10V/cm, pulse-width 180μs, 500Hz, 2min) in serum-free medium, following 24-hour starvation, and in the absence of exogenous EGF ligand, suggesting a ligand-independent pathway for EGFR activation. This ligandless activation was further confirmed by using neutralizing antibodies (LA1) that block the EGFR ligand-binding site. EGFR activation was found to be EGFR kinase dependent, yet with no dimerization following exposure to LEF. ERK activation was found to be mainly a result of EGFR downstream signaling though it partially occurred via EGFR-independent way. We demonstrate that reactive oxygen species and especially decrease in pH generated during exposure to LEF are involved in EGFR ligandless activation. We propose a possible mechanism for the LEF-induced EGFR ligand-independent activation and show activation of other receptor tyrosine kinases following exposure to LEF.

Sunshine and rash: testing the role of sunscreen to prevent epidermal growth factor receptor inhibitor-induced rash

Most patients who receive epidermal growth factor receptor (EGFR) inhibitors develop a rash. To date, no effective palliative therapy has been developed for these rashes. This review describes the rationale behind N05C4, a placebo-controlled trial of sunscreen as an intervention to prevent EGFR inhibitor-related rash.

Differential modulation of stress-inflammation responses by plant polyphenols in cultured normal human keratinocytes and immortalized HaCaT cells

BACKGROUND

Environmental and endogenous stresses to skin are considered causative reasons for skin cancers, premature ageing, and chronic inflammation. Screening of substances with preventive and/or curative properties is currently based on mechanistic studies of their effects towards stress-induced responses in skin cell cultures.

OBJECTIVE

We compared effects of plant polyphenols (PPs) on the constitutive, UVA-, LPS-, or TNF-alpha-induced inflammatory responses in cultured normal human epidermal keratinocytes (NHEK) and immortalized HaCaT cells.

METHODS

Representatives of three classes of PPs, flavonoids, stilbenoids, and phenylpropanoids were studied. Their effects on mRNA were determined by qRT-PCR; protein expression was assayed by Western blot and bioplexed ELISA; phosphorylation of Akt1, ERK1/2, EGFR, and NFkappaB was quantified by intracellular ELISA or Western blot.

RESULTS

PPs or their combination with UVA or LPS induced strong up-regulation of stress responses in HaCaT but not in NHEK. In addition, compared to NHEK, HaCaT responded to TNF-alpha with higher synthesis of MCP-1, IP-10 and IL-8, concomitant with stronger NFkappaB activation. PPs down-regulated the chemokine release from both cell types, although with distinct effects on NFkappaB, Akt1, ERK, and EGFR activation.

CONCLUSION

Results of pharmacological screenings obtained by using HaCaT should be cautiously considered while extending them to primary keratinocytes from human epidermis.

The IGF-1/IGF-1R signaling axis in the skin: a new role for the dermis in aging-associated skin cancer

The appropriate response of human keratinocytes to UVB is dependent on the activation status of the IGF-1 receptor. Keratinocytes grown in conditions where the IGF-1 receptor is inactive, inappropriately replicate in the presence of UVB-induced DNA damage. In human skin epidermal keratinocytes do not express IGF-1, so the IGF-1 receptor on keratinocytes is activated by IGF-1 secreted from dermal fibroblasts. We now demonstrate that the IGF-1 produced by human fibroblasts is essential for the appropriate UVB response of keratinocytes. Furthermore, the expression of IGF-1 is silenced in senescent fibroblasts in vitro. Using quantitative RT-PCR and immunohistochemisty, we can demonstrate that IGF-1 expression is also silenced in geriatric dermis in vivo. The diminished IGF-1 expression in geriatric skin correlates with an inappropriate UVB response in geriatric volunteers. Finally, the appropriate UVB response is restored in geriatric skin in vivo via pretreatment with exogenous IGF-1. These studies provide further evidence for a role of the IGF-1R in suppressing UVB-induced carcinogenesis, suggest that fibroblasts play a critical role in maintaining appropriate activation of the keratinocyte IGF-1R, and imply that reduced expression of IGF-1 in geriatric skin could be an important component in the development of aging-related non-melanoma skin cancer.

G Protein βγ Subunits Augment UVB-induced Apoptosis by Stimulating the Release of Soluble Heparin-binding Epidermal Growth Factor from Human Keratinocytes

UV radiation induces various cellular responses by regulating the activity of many UV-responsive enzymes, including MAPKs. The betagamma subunit of the heterotrimeric GTP-binding protein (Gbetagamma) was found to mediate UV-induced p38 activation via epidermal growth factor receptor (EGFR). However, it is not known how Gbetagamma mediates the UVB-induced activation of EGFR, and thus we undertook this study to elucidate the mechanism. Treatment of HaCaT-immortalized human keratinocytes with conditioned medium obtained from UVB-irradiated cells induced the phosphorylations of EGFR, p38, and ERK but not that of JNK. Blockade of heparin-binding EGF-like growth factor (HB-EGF) by neutralizing antibody or CRM197 toxin inhibited the UVB-induced activations of EGFR, p38, and ERK in normal human epidermal keratinocytes and in HaCaT cells. Treatment with HB-EGF also activated EGFR, p38, and ERK. UVB radiation stimulated the processing of pro-HB-EGF and increased the secretion of soluble HB-EGF in medium, which was quantified by immunoblotting and protein staining. In addition, treatment with CRM179 toxin blocked UV-induced apoptosis, but HB-EGF augmented this apoptosis. Moreover, UVB-induced apoptosis was reduced by inhibiting EGFR or p38. The overexpression of Gbeta(1)gamma(2) increased EGFR-activating activity and soluble HB-EGF content in conditioned medium, but the sequestration of Gbetagamma by the carboxyl terminus of G protein-coupled receptor kinase 2 (GRK2ct) produced the opposite effect. The activation of Src increased UVB-induced, Gbetagamma-mediated HB-EGF secretion, but the inhibition of Src blocked that. Overexpression of Gbetagamma increased UVB-induced apoptosis, and the overexpression of GRK2ct decreased this apoptosis. We conclude that Gbetagamma mediates UVB-induced human keratinocyte apoptosis by augmenting the ectodomain shedding of HB-EGF, which sequentially activates EGFR and p38.

FasL and TRAIL induce epidermal apoptosis and skin ulceration upon exposure to Leishmania major

Receptor-mediated apoptosis is proposed as an important regulator of keratinocyte homeostasis in human epidermis. We have previously reported that Fas/FasL interactions in epidermis are altered during cutaneous leishmaniasis (CL) and that keratinocyte death through apoptosis may play a pathogenic role for skin ulceration. To further investigate the alterations of apoptosis during CL, a keratinocyte cell line (HaCaT) and primary human epidermal keratinocytes were incubated with supernatants from Leishmania major-infected peripheral blood mononuclear cells. An apoptosis-specific microarray was used to assess mRNA expression in HaCaT cells exposed to supernatants derived from L. major-infected cultures. Fas and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mRNA and protein expression were significantly up-regulated, and apoptosis was detected in both HaCaT and human epidermal keratinocyte cells. The keratinocyte apoptosis was partly inhibited through blocking of Fas or FasL and even more efficiently through TRAIL neutralization. Up-regulation of Fas on keratinocytes in epidermis and the presence of FasL-expressing macrophages and T cells in dermis were previously reported by us. In this study, keratinocytes expressing TRAIL, as well as the proapoptotic receptor TRAIL-R2, were detected in skin biopsies from CL cases. We propose that activation of Fas and TRAIL apoptosis pathways, in the presence of inflammatory mediators at the site of infection, leads to tissue destruction and ulceration during CL.

Apoptotic mechanism in pemphigus autoimmunoglobulins-induced acantholysis--possible involvement of the EGF receptor

Pemphigus is an autoimmune cutaneous disease characterized by circulating autoantibodies that cause blistering and erosions on skin and mucous membranes. Circulating autoantibodies bind to epidermal cell membrane and cause cell-cell detachment (acantholysis), leading to epidermal tissue damage and cell death. The principal target of pemphigus vulgaris autoantibodies (PV-IgG) is desmosomal cadherin desmoglein 3 (Dsg3), a constituent of desmosomes, mediating cell-cell adhesion. Several hypotheses for the mechanisms of acantholysis induction by PV-IgG exist, but the actual mechanism is not clear as yet. We have previously reported on apoptosis induction in PV-IgG-mediated epidermal tissue and cell damage as a possible mechanism of acantholysis and cell death (Wang et al. 2004, Apoptosis, 9:131-143). In this study we investigated the involvement of the EGFR and intracellular signal transduction pathways in the PV-IgG-induced apoptosis. We show here that PV-IgG induced activation/autophosphorylation of EGFR in cultured keratinocytes in vitro. The specific tyrosine kinase inhibitor AG1478 abrogated EGFR autophosphorylation, cell death, FasL appearance and acantholysis, all induced by PV-IgG, in parallel, confirming the involvement of EGFR in this Fas apoptotic cascade. Activation of EGFR was followed by phosphorylation of its downstream substrates, MAP kinase ERK and transcription factor c-Jun, and internalization of EGFR. Pharmacological inactivation of the EGFR and ERK kinase activities, by use of specific inhibitors AG1478 and PD98059 respectively, blocked PV-IgG-induced phosphorylation of EGFR, ERK and c-Jun and cellular apoptosis, measured by flow cytometry and caspase 3 activity. Prolonged activation of EGFR by PV-IgG led to dramatic internalization of this receptor, possibly reducing the ability of the cell to perform survival signals. This suggests that activation of EGFR, followed by its internalization, is pivotal for intracellular apoptotic signal transduction via ERK/c-Jun pathways, leading to acantholysis. Our experimental data indicate that the EGFR is instrumental in transducing apoptotic/acantholytic signals in keratinocytes cultures in response to PV-IgG treatment. The acantholytic effect caused by PV-IgG binding to cell surface receptors begins with and depends on cell surface receptor (EGFR) activation of intracellular signaling pathways (ERK pathway) and apoptosis induction (FasR pathway), which later lead to major cell-cell separation (acantholysis) and cell death.

A keratinocyte's course of life

An adequate permeability barrier function of the mammalian epidermis is guaranteed by the characteristic architecture of the stratum corneum. This uppermost layer consists of a highly organized extracellular lipid compartment which is tightly joined to the corneocytes. The generation of the extracellular lipid compartment and the transformation of the keratinocytes into corneocytes are the main features of epidermal differentiation. However, equally important is the continuous renewal of the stratum corneum, which is insured by a careful balance between the replenishment of new keratinocytes from the proliferating basal layer, and the well-orchestrated loss of the most superficial cells after the so-called 'epidermal programmed cell death'. In this overview, the complete life of keratinocytes is described, from the proliferative organization to the process of desquamation.

Aberrant NF-κB Activity in HaCaT Cells Alters their Response to UVB Signaling

The immortalized keratinocyte cell line called HaCaT has been used in experiments as a convenient substitute for cultured normal human keratinocytes. However, some molecular differences have been identified that distinguish HaCaT cells from normal human keratinocytes, including differences in the NF-kappaB signaling pathway and in their response to UVB irradiation. NF-kappaB is a widely expressed transcription factor that is activated by a cacophony of stimuli, including inflammatory mediators such as TNFalpha and oxidative stressors such as UVB exposure. This report delineates and further elucidates the aberrant NF-kappaB signaling pathway and its effect in HaCaT cells exposed to UVB radiation or inflammatory mediators. We demonstrate that NF-kappaB DNA binding is activated by both UVB and TNFalpha, but discrepancies in the activation of key upstream signaling pathway components such as AKT phosphorylation and IkappaBalpha degradation exist. Disruption of the constitutive NF-kappaB activity in HaCaT cells resulted in alterations in NF-kappaB signaling that were more consistent with the NF-kappaB signaling pathway in normal human keratinocytes. These studies suggest that caution should be used in extrapolating the biological responses of HaCaT cells to those of normal human keratinocytes in the absence of confirmatory experiments.

Bax activation and translocation to mitochondria mediate EGF-induced programmed cell death

The ErbB family of receptor tyrosine kinases is involved in the regulation of cell proliferation, differentiation and apoptosis. Previous studies indicate that cells expressing elevated levels of the EGFR and ErbB-2 undergo programmed cell death in response to EGF or other EGFR ligands. However, the detailed mechanisms of EGF-induced apoptosis are unclear. This report demonstrates that in the cells undergoing EGF-dependent apoptosis Bax changes its conformation and forms multimeric aggregates, which accumulate on the mitochondrial membrane. Bax activation and translocation to the mitochondria induces a loss of mitochondrial transmembrane potential and cell death. Also, during EGF-induced apoptosis there is downregulation of Bcl-xL, an anti-apoptotic protein. Expression of Bcl-xL in cells susceptible to EGF-dependent apoptosis prevents cell death. The data indicate that addition of EGF does not result in a significant release of cytochrome c from mitochondria and EGF-induced apoptosis is mainly caspase independent.

Expression of mutant human epidermal receptor 3 attenuates lung fibrosis and improves survival in mice

Neuregulin-1 (NRG-1), binding to the human epidermal growth factor receptor HER2/HER3, plays a role in pulmonary epithelial cell proliferation and recovery from injury in vitro. We hypothesized that activation of HER2/HER3 by NRG-1 would also play a role in recovery from in vivo lung injury. We tested this hypothesis using bleomycin lung injury of transgenic mice incapable of signaling through HER2/HER3 due to lung-specific dominant-negative HER3 (DNHER3) expression. In animals expressing DNHER3, protein leak, cell infiltration, and NRG-1 levels in bronchoalveolar lavage fluid increased after injury, similar to that in nontransgenic littermate control animals. However, HER2/HER3 was not activated, and DNHER3 animals displayed fewer lung morphological changes at 10 and 21 days after injury (P = 0.01). In addition, they contained 51% less collagen in injured lungs (P = 0.04). Transforming growth factor-beta1 did not increase in bronchoalveolar lavage fluid from DNHER3 mice compared with nontransgenic littermate mice (P = 0.001), suggesting that a mechanism for the decreased fibrosis was lack of transforming growth factor-beta1 induction in DNHER3 mice. Severe lung injury (0.08 units bleomycin) resulted in 80% mortality of nontransgenic mice, but only 35% mortality of DNHER3 transgenic mice (P = 0.04). Thus inhibition of HER2/HER3 signaling protects against pulmonary fibrosis and improves survival.

Overexpression of ErbB-2 Protein in Human Middle Ear Cholesteatomas

OBJECTIVE

The purpose of this study is to verify the hypothesis that ErbB-2 protein is overexpressed in human middle ear cholesteatomas and to elucidate the relationship between overexpression of ErbB-2 protein, cell proliferation, and apoptosis.

STUDY DESIGN

Prospective review of 20 patients between 2001 and 2003 with middle ear cholesteatoma.

METHODS

Middle ear cholesteatoma matrix and retroauricular skin were immunostained with anti-ErbB-2, Ki-67, and single-stranded DNA (ssDNA) antibody. The distribution of immunoreactivity to these antibodies and labeling indices were compared between cholesteatoma and retroauricular skin.

RESULTS

In matrix of middle ear cholesteatoma, ErbB-2 and ssDNA were expressed in the keratinocytes of all layers and Ki-67 was expressed in the keratinocytes of the basal, lower spinous, and occasionally granular layer. In retroauricular skin, ErbB-2 and Ki-67 were expressed in the keratinocytes of the basal and occasionally lower spinous layer and ssDNA was expressed in the keratinocytes of all layers. Labeling indices against anti-ErbB-2, Ki-67, and ssDNA antibody were significantly greater in cholesteatoma as compared with retroauricular skin.

CONCLUSIONS

In cases of cholesteatoma, ErbB-2 protein was overexpressed and cell proliferation and apoptosis of keratinocytes were accelerated. ErbB-2 protein could modulate terminal differentiation and apoptosis in the keratinocytes of all layers in cholesteatoma matrix and cell proliferation in the keratinocytes of the basal and lower spinous layer in normal skin.

Role of HER receptors family in development and differentiation

Members of the epidermal growth factor receptor family of receptor tyrosine kinases play a critical role in both development and oncogenesis. The latter is suggested by the frequent overexpression of HER-2, EGFR, and HER-3 in some human carcinomas, primarily breast and squamous cancer. The biological activities of the EGFR family are exerted through various ligand-receptor and receptor-receptor interactions. One receptor that plays a central role in this signaling network is HER-2/Neu, which is considered the preferred heterodimerization partner for other members of the EGFR family. The role of these receptors and their ligands in development is discussed, with particular emphasis on their ability to mediate a variety of pathways and cellular responses, including proliferation, differentiation, and apoptosis.