Human Papillary and Reticular Fibroblasts Show Distinct Functions on Tumor Behavior in 3D-Organotypic Cultures Mimicking Melanoma and HNSCC

Human dermis can be morphologically divided into the upper papillary and lower reticular dermis. Previously, we demonstrated that papillary (PFs) and reticular (RFs) fibroblasts show distinct morphology and gene expression profiles. Moreover, they differently affect tumor invasion and epithelial-to-mesenchymal transition (EMT) in in vitro 3D-organotypic cultures of cutaneous squamous cell carcinoma (cSCC). In this study, we examined if these distinct effects of PFs and RFs can be extrapolated in other epithelial/non-epithelial tumors such as melanoma and head and neck squamous cell carcinoma (HNSCC). To this end, 3D-Full-Thickness Models (FTMs) were established from melanoma (AN and M14) or HNSCC cell lines (UM-SCC19 and UM-SCC47) together with either PFs or RFs in the dermis. The interplay between tumor cells and different fibroblasts was investigated. We observed that all the tested tumor cell lines showed significantly stronger invasion in RF-FTMs compared to PF-FTMs. In addition, RF-FTMs demonstrated more tumor cell proliferation, EMT induction and basement membrane disruption. Interestingly, RFs started to express the cancer-associated fibroblast (CAF) biomarker α-SMA, indicating reciprocal interactions eventuating in the transition of RFs to CAFs. Collectively, in the melanoma and HNSCC FTMs, interaction of RFs with tumor cells promoted EMT and invasion, which was accompanied by differentiation of RFs to CAFs.

A shift from papillary to reticular fibroblasts enables tumour-stroma interaction and invasion

Background

Tumour stroma consists of a heterogeneous population of fibroblasts and related mesenchymal cells, collectively dubbed cancer-associated fibroblasts (CAFs). These CAFs are key players in cancer invasion of cutaneous squamous cell carcinoma (SCC). As we have shown earlier, papillary and reticular fibroblasts (Pfs and Rfs, respectively) have distinct effects on epidermal and dermal homeostasis, but their role in cancer invasion and epithelial-to-mesenchymal transition (EMT) remains to be determined.

Methods

We used 3D cultures of human skin equivalents (HSEs) to analyse the effects of Pfs and Rfs on the invasive behaviour of SCC and EMT.

Results

We reveal for the first time the importance of Pfs versus Rfs in SCC invasion and EMT. Cell lines from different stages of SCC showed significantly more extensive invasion into a dermis composed of Rfs than of Pfs. In addition, Rfs-based HSEs showed increased cell activation and stained positive for CAF biomarkers α-SMA and vimentin. Further analysis revealed that invasively growing cancer cells in Rf-HSEs express markers of EMT transition, like SNAIL2, N-cadherin and ZEB1.

Conclusions

Conversely, our results show that Pfs contain cancer cells more within the epidermis. Rfs are clearly predisposed to differentiate into CAFs upon SCC signals, assisting invasion and EMT.

The Evaluation of Noninvasive Measurements of Erythema as a Potential Surrogate for DNA Damage in Repetitively UV-exposed Human Skin

Erythema (i.e. visible redness) and DNA damage caused by ultraviolet radiation (UVR) in human skin have similar action spectra and show good correlation after a single exposure to UVR. We explored the potential to use instrumental assessments of erythema as a surrogate for DNA damage after repeated exposures to UVR. We exposed 40 human subjects to three different exposure schedules using two different UVR sources. Cyclobutane-pyrimidine dimers (CPDs) in skin biopsies were measured by immunofluorescence, and erythema was assessed by both the Erythemal Index (EI) and the Oxy-hemoglobin (Oxy-Hb) content. Surprisingly, the skin with the highest cumulative dose ended up with the lowest level of DNA damage, and with the least erythema, as assessed by Oxy-Hb (but not EI) 24 h after the last UV exposure. Although the level of CPDs, on average, paralleled Oxy-Hb (R² = 0.80-0.94, P = 0.03-0.11), the correlation did not hold for the pooled individual measurements (R² = 0.009, P = 0.37) due to potential individual differences in UV-induced photoadaptation. We suggest that the methodology may be optimized to improve the correlation between DNA damage level and erythema to enable noninvasive risk assessment based on erythema/Oxy-Hb content for individual human subjects.

Fractionation of a tumor-initiating UV dose introduces DNA damage-retaining cells in hairless mouse skin and renders subsequent TPA-promoted tumors non-regressing

Sunburns and especially sub-sunburn chronic UV exposure are associated with increased risk of squamous cell carcinomas (SCCs). Here we focus on a possible difference in tumor initiation from a single severe-sunburn dose (on day 1, 21 hairless mice) and from an equal dose fractionated into very low sub-sunburn doses not causing any (growth-promoting) epidermal hyperplasia (40 days daily exposure, n=20). From day 47 all mice received 12-O-Tetradecanoylphorbol-13-acetate (TPA) applications (2x/wk) for 20 weeks to promote tumor development within the lifetime of the animals. After the sub-sunburn regimen sparse DNA damage-retaining basal cells (quiescent stem cells, QSCs) remained in the non-hyperplastic epidermis. These cells were forced to divide by TPA. After discontinuation of TPA tumors regressed and disappeared in the ‘sunburn group’ but persisted and grew in the ‘sub-sunburn group’ (0.06 vs 2.50 SCCs and precursors ≥4mm/mouse after 280 days, p=0.03). As the tumors carried no mutations in p53, H/K/N-Ras and Notch1/2, these ‘usual suspects' were not involved in the UV-driven tumor initiation. Although we could not selectively eliminate QSCs (unknown phenotype) to establish causality, our data suggest that forcing specifically DNA damage-retaining QSCs to divide – with high mutagenic risk - gives rise to persisting (mainly ‘in situ’) skin carcinomas.

A systematic review of the influence of skin pigmentation on changes in the concentrations of vitamin D and 25-hydroxyvitamin D in plasma/serum following experimental UV irradiation

Does skin colour influence the production of vitamin D metabolites following UV irradiation? The paper reviews the studies addressing this important question and discusses possible reasons for the contradictory results.

Analysis of mutant frequencies and mutation spectra in hMTH1 knockdown TK6 cells exposed to UV radiation

Ultraviolet radiation is a highly mutagenic agent that damages the DNA by the formation of mutagenic photoproducts at dipyrimidine sites and by oxidative DNA damages via reactive oxygen species (ROS). ROS can also give rise to mutations via oxidation of dNTPs in the nucleotide pool, e.g. 8-oxo-dGTP and 2-OH-dATP and subsequent incorporation during DNA replication. Here we show that expression of human MutT homolog 1 (hMTH1) which sanitizes the nucleotide pool by dephosphorylating oxidized dNTPs, protects against mutagenesis induced by long wave UVA light and by UVB light but not by short wave UVC light. Mutational spectra analyses of UVA-induced mutations at the endogenous Thymidine kinase gene in human lymphoblastoid cells revealed that hMTH1 mainly protects cells from transitions at GC and AT base pairs.

Differential role of UVB-induced photolesions in skin and immune response. (50.10)

UV-induced DNA damage is an essential step in the process by which UVB can alter host resistance to infections diseases. UV-light induces two types of photolesion on DNA that are repaired by photolyases (absent in placental mammals) or Nucleotide Excision Repair. Photolyases are capable of repair these lesions using a photon of light as source of energy. Although the deleterious effects of UV are widely known, the specific role of each photolesion in the induction of changes in the immune response remains unknown. It has been shown in vivo that CPDs are responsible for the majority of the effects after UVB skin irradiation of DNA repair proficient mice, such as erythema, apoptosis, hyperplasia, tumorigenesis and immunosuppression. However the role of 6-4PP is still unknown. We show that the removal of CPD lesions prevents hyperplasia and induces dark skin pigmentation. When 6-4PPs were removed, UVB promoted hyperplasia and tanning. Also, unlike 6-4PP removal, CPD removal is capable of preventing the development of p53 epidermal patches, which have a direct correlation with carcinoma development. Furthermore, the CPD removal is sufficient to suppress the induction of Treg (CD4+CD25+Foxp3) in draining lymph nodes and spleen indicating a minor state of immunosuppression. This study can provide new information as how immune responses are regulated depending of the lesion that is repaired and improve our understanding the immune system role in skin cancer induction.

Susceptibility to UV-A and UV-B Provocation Does Not Correlate With Disease Severity of Polymorphic Light Eruption

OBJECTIVE

To examine whether the ease of disease provocation by UV-A and/or UV-B radiation correlates with clinical features of polymorphic light eruption (PLE), including those indicative of disease severity.

DESIGN

Intervention study.

PATIENTS

One hundred forty-three patients with PLE.

INTERVENTIONS

Provocation testing with broadband UV-A and UV-B lamps. Additionally, a range of clinical characteristics of the disorder, including a 5-item PLE severity score, was assessed by questionnaire.

MAIN OUTCOME MEASURES

Percentage of PLE rash induction by UV-A and UV-B provocation, differences between the skin types, and correlation between the results of provocation and a range of clinical characteristics of the disorder, including a 5-item PLE severity score.

RESULTS

Rash provocation was seen in 78.3% of patients after UV-A and in 46.7% after UV-B exposure. Neither UV-A nor UV-B provocation showed a significant association with the total 5-item severity score. The UV-B reactivity was associated with a high score on the severity item "number of months affected per year" (P = .04), whereas UV-A responsiveness showed a tendency for association with facial involvement (P = .06).

CONCLUSION

The objective assessment of UV-A or UV-B susceptibility in this large group of patients showed no significant relationship with clinical disease severity.

Rapid and Continuous Increases in Incidence Rates of Basal Cell Carcinoma in the Southeast Netherlands Since 1973

This study is aimed to determine the characteristics of the trends in incidence of basal cell carcinoma (BCC) in the Netherlands. We used incidence data of BCC from the Eindhoven Cancer Registry (Comprehensive Cancer Centre South) in the south of the Netherlands from 1973 to 2000. Data were age-adjusted and age-specific rates were calculated. Joinpoint and age-period-birth cohort modelling were applied. Between 1973 and 2000, age-adjusted incidence rates of BCC increased in both sexes, most markedly among (young) females. Recent increases were most marked on the trunk. The male data fitted age-drift models, suggesting a linear increase in rates over time, not attributable to either period- or cohort effects. In females, age-cohort-drift models described the data adequately, suggesting changes in intermittent UV exposures in subsequent cohorts. Incidence of BCC in the Netherlands is increasing rapidly, especially at body sites that are not chronically exposed to sunlight. The most likely explanation is an increased intermittent overexposure to UV radiation. This could have introduced an equal fractional increase in risk at all ages in all cohorts. There is no indication of an end to this trend in BCC.