Targeting 14-3-3ε activates apoptotic signaling to prevent cutaneous squamous cell carcinoma.

More than a million cases of cutaneous squamous cell carcinoma are diagnosed in the USA each year, and its incidence is increasing. Most of these malignancies arise from premalignant lesions, providing an opportunity for intervention before malignant progression. We previously documented how cytoplasmic mislocalization of CDC25A in premalignant and malignant skin cancers confers resistance to apoptotic cell death via a mechanism that depends on its interaction with 14-3-3ε. From these data, we hypothesized that 14-3-3ε overexpression drives skin tumor development and progression, such that targeting 14-3-3ε may be a useful strategy for skin cancer treatment. Like CDC25A, 14-3-3ε was overexpressed and mislocalized to the cytoplasm of both benign and malignant human skin cancer. Skin-targeted deletion of the 14-3-3ε gene reduced skin tumor development by 75% and blocked malignant progression. 14-3-3ε suppressed apoptosis through activation of Akt, leading to inhibition of BCL2 associated agonist of cell death and upregulation of Survivin. Using virtual tetrapeptide libraries, we developed a novel peptide that specifically blocked 14-3-3ε heterodimerization and thereby prevented its interaction with CDC25A. The peptide reduced prosurvival signaling, killed skin cancer cells and reduced skin tumor growth in xenograft. Normal skin keratinocytes were unaffected by inhibition or deletion of 14-3-3ε. Thus, targeting of 14-3-3ε dimerization is a promising strategy for the treatment of premalignant skin lesions.

Multiple or familial café-au-lait spots is neurofibromatosis type 6: clarification of a diagnosis.

A café-au-lait macule (CALM) is an evenly pigmented macule or patch of variable size. Solitary CALMs are common birthmarks in up to 2.5 percent of normal neonates and their incidence rises to up to 25 percent in preschool-aged children. Two or more CALMs occur much less frequently. Multiple lesions may warrant investigation to identify an underlying disease including neurofibromatosis types 1 (NF1), neurofibromatosis type 2, McCune-Albright syndrome, and neurofibromatosis type 1-like syndrome. Considered a hallmark and diagnostic criteria for NF1 is the presence of 6 or more CALMs greater than 0.5 cm in prepubertal individuals. Rare reports describe families which demonstrate the phenomenon of multiple CALMs without other stigmata of NF1 or evidence of other systemic disease. Herein is a description of the condition and justification for this entity to be named Neurofibromatosis type 6.

Erbb2 suppresses DNA damage-induced checkpoint activation and UV-induced mouse skin tumorigenesis.

The Erbb2 receptor is activated by UV irradiation, the primary cause of non-melanoma skin cancer. We hypothesized that Erbb2 activation contributes to UV-induced skin tumorigenesis by suppressing cell cycle arrest. Consistent with this hypothesis, inhibition of Erbb2 in v-ras(Ha) transgenic mice before UV exposure resulted in both 56% fewer skin tumors and tumors that were 70% smaller. Inhibition of the UV-induced activation of Erbb2 also resulted in milder epidermal hyperplasia, S-phase accumulation, and decreased levels of the cell cycle regulator Cdc25a, suggesting altered cell cycle regulation on inhibition of Erbb2. Further investigation using inhibition or genetic deletion of Erbb2 in vitro revealed reduced Cdc25a levels and increased S-phase arrest in UV-irradiated cells lacking Erbb2 activity. Ectopic expression of Cdc25a prevented UV-induced S-phase arrest in keratinocytes lacking Erbb2 activity, demonstrating that maintenance of Cdc25a by Erbb2 suppresses cell cycle arrest. Examination of checkpoint pathway activation upstream of Cdc25a revealed Erbb2 activation did not alter Ataxia Telangiectasia and Rad3-related/Ataxia Telangiectasia Mutated activity but increased inhibitory phosphorylation of Chk1-Ser(280). Since Akt phosphorylates Chk1-Ser(280), the effect of Erbb2 on phosphatidyl inositol-3-kinase (PI3K)/Akt signaling during UV-induced cell cycle arrest was determined. Erbb2 ablation reduced the UV-induced activation of PI3K while inhibition of PI3K/Akt increased UV-induced S-phase arrest. Thus, UV-induced Erbb2 activation increases skin tumorigenesis through inhibitory phosphorylation of Chk1, Cdc25a maintenance, and suppression of S-phase arrest via a PI3K/Akt-dependent mechanism.

Multiple mechanisms of Erbb2 action after ultraviolet irradiation of the skin.

Ultraviolet (UV) irradiation causes multiple pathologic changes in the skin including inflammation, immune suppression, photoaging, and cancer. Effects of UV irradiation include the activation of numerous signal transduction pathways, including the mitogen-activated protein kinases (MAPK), and the activation of transcription factors such as nuclear factor kappa B (NFkappaB). These responses alter gene expression in a manner that resembles the response to growth factors known as the "UV response". The UV response alters the kinetics of cell division and cell death allowing the skin to recover from the DNA damage caused by UV exposure. UV irradiation also rapidly activates epidermal growth factor receptor (EGFR) family members, including Erbb2 (human epithelial growth factor receptor 2 (HER2)/neu), through the generation of reactive oxygen species. Erbb2, a protooncogene that is activated in many types of cancer and associated with aggressive and chemotherapeutic-resistant disease, is expressed in both follicular and epidermal keratinocytes within the skin. However, the physiological functions of Erbb2 in the skin and its role in the UV response are largely unknown. In this review, evidence that Erbb2 is influential in modulating the response of the skin to UV will be presented. Erbb2 alters the expression of regulatory genes controlling inflammation, angiogenesis, cell division, apoptosis, cell adhesion, and migration following UV irradiation. In addition, Erbb2 dampens UV-induced S-phase arrest, augments inflammation in response to UV irradiation, and suppresses UV-induced apoptosis. In summary, the evidence presented herein links UV-induced Erbb2 activation to many of the effects of UV and implicates Erbb2 in UV-induced carcinogenesis.

Erbb2 regulates inflammation and proliferation in the skin after ultraviolet irradiation.

Exposure to ultraviolet (UV) irradiation is the major cause of nonmelanoma skin cancer, the most common form of cancer in the United States. UV irradiation has a variety of effects on the skin associated with carcinogenesis, including DNA damage and effects on signal transduction. The alterations in signaling caused by UV regulate inflammation, cell proliferation, and apoptosis. UV also activates the orphan receptor tyrosine kinase and proto-oncogene Erbb2 (HER2/neu). In this study, we demonstrate that the UV-induced activation of Erbb2 regulates the response of the skin to UV. Inhibition or knockdown of Erbb2 before UV irradiation suppressed cell proliferation, cell survival, and inflammation after UV. In addition, Erbb2 was necessary for the UV-induced expression of numerous proinflammatory genes that are regulated by the transcription factors nuclear factor-kappaB and Comp1, including interleukin-1beta, prostaglandin-endoperoxidase synthase 2 (Cyclooxygenase-2), and multiple chemokines. These results reveal the influence of Erbb2 on the UV response and suggest a role for Erbb2 in UV-induced pathologies such as skin cancer.