Increased Fas ligand expression by T cells and tumour cells in the progression of actinic keratosis to squamous cell carcinoma

Prognostic Value of Fas/Fas Ligand Expression on Circulating Tumor Cells (CTCs) and Immune Cells in the Peripheral Blood of Patients with Metastatic Breast Cancer

The Fas/Fas ligand (FasL) system is a major apoptosis-regulating pathway with a key role in tumor immune surveillance and metastasis. The expression of Fas/FasL on mammary tumor tissues holds prognostic value for breast cancer (BC) patients. We herein assessed Fas/FasL expression on circulating tumor cells (CTCs) and matched peripheral blood mononuclear cells (PBMCs) from 98 patients with metastatic BC receiving first-line treatment. Fas+, FasL+, and Fas+/FasL+ CTCs were identified in 88.5%, 92.3%, and 84.6% of CTC-positive patients, respectively. In addition, Fas+/FasL+, Fas-/FasL+, and Fas-/FasL- PBMCs were identified in 70.3%, 24.2%, and 5.5% of patients, respectively. A reduced progression-free survival (PFS) was revealed among CTC-positive patients (median PFS: 9.5 versus 13.4 months; p = 0.004), and specifically among those harboring Fas+/FasL+ CTCs (median PFS: 9.5 vs. 13.4 months; p = 0.009). On the other hand, an increased overall survival (OS) was demonstrated among patients with Fas+/FasL+ PBMCs rather than those with Fas-/FasL+ and Fas-/FasL- PBMCs (median OS: 35.7 vs. 25.9 vs. 14.4 months, respectively; p = 0.008). These data provide for the first time evidence on Fas/FasL expression on CTCs and PBMCs with significant prognostic value for patients with metastatic BC, thus highlighting the role of the Fas/FasL system in the peripheral immune response and metastatic progression of BC.

The Impact of Notch Signaling for Carcinogenesis and Progression of Nonmelanoma Skin Cancer: Lessons Learned from Cancer Stem Cells, Tumor Angiogenesis, and Beyond

Since many decades, nonmelanoma skin cancer (NMSCs) is the most common malignancy worldwide. Basal cell carcinomas (BCC) and squamous cell carcinomas (SCC) are the major types of NMSCs, representing approximately 70% and 25% of these neoplasias, respectively. Because of their continuously rising incidence rates, NMSCs represent a constantly increasing global challenge for healthcare, although they are in most cases nonlethal and curable (e.g., by surgery). While at present, carcinogenesis of NMSC is still not fully understood, the relevance of genetic and molecular alterations in several pathways, including evolutionary highly conserved Notch signaling, has now been shown convincingly. The Notch pathway, which was first developed during evolution in metazoans and that was first discovered in fruit flies (Drosophila melanogaster), governs cell fate decisions and many other fundamental processes that are of high relevance not only for embryonic development, but also for initiation, promotion, and progression of cancer. Choosing NMSC as a model, we give in this review a brief overview on the interaction of Notch signaling with important oncogenic and tumor suppressor pathways and on its role for several hallmarks of carcinogenesis and cancer progression, including the regulation of cancer stem cells, tumor angiogenesis, and senescence.

Human papillomavirus E7 oncoprotein expression by keratinocytes alters the cytotoxic mechanisms used by CD8 T cells

Cervical cancer is a malignant transformation of keratinocytes initiated by the E7 oncoprotein of human papillomavirus (HPV). These tumors are characterized by keratinocyte hyperproliferation and are often infiltrated with activated CD8 T cells. HPV infection confers changes to gain immunological advantage to promote chronic infection, and these persist with malignant transformation. We investigated the relative importance of the many redundant mechanisms of cytotoxicity used by CD8 T cells to kill keratinocytes expressing HPV E7 oncoprotein using extended-duration time-lapse microscopy that allows examination of cell-to-cell interactions during killing. E7 expression by keratinocytes increased susceptibility to cell-mediated killing. However, while killing of non-transgenic keratinocytes was traditional, perforin-mediated, and caspase-dependent, E7-expression favored killing by perforin-independent, caspase-independent mechanisms. The roles of perforin, TNFα, IFNγ, Fas/FasL and PD1/PD-L1 were graded according to target cell survival to produce a hierarchy of killing mechanisms utilized in killing E7-expressing cells. TNFα was essential for perforin-mediated killing of E7-expressing cells, but not perforin-independent killing. IFNγ facilitated killing by Fas/FasL interaction, especially in the absence of perforin. Additionally, expression of E7 offered protection from killing by up regulation of PD-L1, Fas and FasL expression on keratinocytes promoting fight-back by target cells, resulting in effector cell death. This study shows that keratinocytes expressing E7 are highly susceptible to killing by CD8 T cells, but utilizing different armamentarium. Down-regulation of CD8 T cell cytotoxicity in HPV-related tumors may be due to suppression by E7-expressing keratinocytes. Immunotherapy for HPV-related cancers may be improved by suppression of PD-L1, or by suppression of FasL.

Notch signaling is significantly suppressed in basal cell carcinomas and activation induces basal cell carcinoma cell apoptosis

A subset of basal cell carcinomas (BCCs) are directly derived from hair follicles (HFs). In some respects, HFs can be defined as 'ordered' skin appendage growths, while BCCs can be regarded as 'disordered' skin appendage growths. The aim of the present study was to examine HFs and BCCs to define the expression of common and unique signaling pathways in each skin appendage. Human nodular BCCs, along with HFs and non‑follicular skin epithelium from normal individuals, were examined using microarrays, qPCR, and immunohistochemistry. Subsequently, BCC cells and root sheath keratinocyte cells from HFs were cultured and treated with Notch signaling peptide Jagged1 (JAG1). Gene expression, protein levels, and cell apoptosis susceptibility were assessed using qPCR, immunoblotting, and flow cytometry, respectively. Specific molecular mechanisms were found to be involved in the process of cell self‑renewal in the HFs and BCCs, including Notch and Hedgehog signaling pathways. However, several key Notch signaling factors showed significant differential expression in BCCs compared with HFs. Stimulating Notch signaling with JAG1 induced apoptosis of BCC cells by increasing Fas ligand expression and downstream caspase-8 activation. The present study showed that Notch signaling pathway activity is suppressed in BCCs, and is highly expressed in HFs. Elements of the Notch pathway could, therefore, represent targets for the treatment of BCCs and potentially in hair follicle engineering.

Pathobiology of actinic keratosis: ultraviolet-dependent keratinocyte proliferation

Actinic keratoses are proliferations of transformed neoplastic keratinocytes in the epidermis that are the result of cumulative ultraviolet (UV) radiation from sun exposure. They are commonly found on sites of sun-exposed skin such as the face, balding scalp, and back of the hand. Although UV exposure does exert certain beneficial effects on the skin, excessive exposure to UV radiation induces multiple cascades of molecular signaling events at the cellular level that produce inflammation, immunosuppression, failure of apoptosis, and aberrant differentiation. Cumulatively, these actions result in mutagenesis and, ultimately, carcinogenesis. This article provides a brief overview of the key mediators that are implicated in the pathobiology of actinic keratosis. Three evolutionary possibilities exist for these keratoses in the absence of treatment: (1) spontaneous remission, which can be common; (2) remaining stable, without further progression; or (3) transformation to invasive squamous cell carcinoma, which may metastasize. Because the effects of UV radiation on the skin are complex, it is not yet fully clear how all of the mediators of actinic keratosis progression are interrelated. Nonetheless, some represent potential therapeutic targets, because it is clear that directing therapy to the effects of UV radiation at a number of different levels could interrupt and possibly reverse the mechanisms leading to malignant transformation.

Aberrant expression of Fas and FasL pro-apoptotic proteins in basal cell and squamous cell carcinomas

BACKGROUND

Fas and FasL are cell-surface receptors involved in apoptosis. Aim.  To investigate Fas and FasL expression levels in basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) to gain an insight into the mechanisms of Fas/FasL apoptosis and immune evasion in epidermal tumours.

METHODS

Real-time PCR and streptavidin-biotin immunohistochemistry techniques were used to detect Fas and FasL expression in BCC, SCC and normal skin specimens.

RESULTS

Fas and FasL mRNA expression and immunostaining levels were lower in the 21 BCC specimens than in normal skin, whereas they were higher in the 15 SCC specimens than in normal skin.

CONCLUSION

FasL immunostaining correlated with the capability of the tumour to invade and metastasize; the absent or weak immunostaining in the BCC specimens correlated with low capability, and the strong staining in the SCC specimens correlated with high capability.

FLIP ing the coin? Death receptor-mediated signals during skin tumorigenesis

Keratinocyte skin cancer is a multi-step process, during which a number of obstacles have to be overcome by the tumor cell to allow the development of a manifest tumor. Beside proliferation and immortality, apoptosis resistance is one additional and critical step during skin carcinogenesis. Over the past two decades, much has been learned about the prototypical membrane-bound inducers of apoptosis, namely the death receptors and their ligands, and the apoptosis signalling pathways activated by death receptors have been elucidated in great detail. In contrast, much less is known about the tissue-specific role of the death receptor/ligands systems during the development of skin cancer. Here, we summarize and discuss the role of this intriguing receptor family and the potential mechanistical impact of the intracellular caspase-8 inhibitor cFLIP for keratinocyte skin cancer. Given more recent data about cFLIP and its isoforms, a more complex regulatory role of cFLIP can be suspected. Indeed, cFLIP may not solely interfere with death receptor-mediated apoptosis signalling pathways, but may positively or negatively influence other, potential harmful signalling pathways such as the production of inflammatory cytokines, tumor cell migration or the activation of transcription factors such as NF-kappaB, considered crucial during skin tumorigenesis. In this respect, cFLIP may act to 'FLIP the coin' during the development of keratinocyte skin cancer.