Trends in the treatment and prevention of keratinocyte carcinoma (non-melanoma skin cancer)

Identification and pharmacological modification of resistance mechanisms to protoporphyrin-mediated photodynamic therapy in human cutaneous squamous cell carcinoma cell lines

BACKGROUND

Photodynamic therapy (PDT) is clinically approved to treat neoplastic skin diseases such as precursors of cutaneous squamous cell carcinoma (cSCC). In PDT, 5-aminolevulinic acid (5-ALA) drives the selective formation of the endogenous photosensitizer protoporphyrin IX (PpIX). Although 5-ALA PDT is clinically highly effective, resistance might occur due to decreased accumulation of PpIX in certain tumors. Such resistance may be caused by any fundamental step of PpIX accumulation: 5-ALA uptake, PpIX synthesis and PpIX efflux.

METHODS

We investigated PpIX accumulation and photodynamically induced cell death in PDT refractory SCC-13, PDT susceptible A431, and normal human epidermal keratinocytes (NHEK). Expression of genes associated with cellular PpIX kinetics was investigated on mRNA and protein level. PpIX accumulation and cell death upon illumination were pharmacologically manipulated using drugs targeting 5-ALA uptake, PpIX synthesis or efflux.

RESULTS

The experiments indicate that taurine transporter (SLC6A6) is the major pathway for 5-ALA uptake in cSCC cells, while being less important in NHEK. Downregulation of PpIX synthesis enzymes in SCC-13 was counteracted by methotrexate (MTX) treatment, which restored PpIX formation and cell death. PpIX efflux inhibitors targeting ABC transporters led to significantly increased PpIX accumulation in SCC-13, thereby fully overcoming resistance.

CONCLUSIONS

The results indicate a conserved threshold for PpIX accumulation with respect to PDT-resistance. Cells showed increased viability after PDT at PpIX concentrations below 1.5 nM. Selective uptake of 5-ALA via taurine transporter SLC6A6 in cutaneous tumor cells is novel but unrelated to resistance. MTX can partially abrogate resistance by PpIX synthesis enzyme induction, while efflux mechanisms via ABC transporters seem the main driving force and promising drug targets.

Dihydroartemisinin inhibits activation of the AIM2 inflammasome pathway and NF-κB/HIF-1α/VEGF pathway by inducing autophagy in A431 human cutaneous squamous cell carcinoma cells

The therapeutic effect of dihydroartemisinin (DHA) against cutaneous squamous cell carcinoma (cSCC) has been previously demonstrated; however, the underlying mechanism remains unclear. This study sought to verify the therapeutic effect of DHA against cSCC and explore its underlying mechanism in A431 cSCC cells. This study reported that DHA inhibited A431 cells proliferation in a time- and concentration-dependent manner and promoted A431 cells apoptosis. Moreover, DHA inhibited the invasion and migration of A431 cells. Mechanistically, DHA promoted autophagy and inhibited activation of the absent in melanoma 2 (AIM2) inflammasome pathway and NF-κB/HIF-1α/VEGF pathway. Treatment of A431 cells with the mTOR inhibitor, and autophagy promoter, rapamycin also inhibited these two pathways. In conclusion, DHA inhibited activation of the AIM2 inflammasome pathway and NF-κB/HIF-1α/VEGF pathway by promoting autophagy in A431 cells, thus accounting for its therapeutic effect. Induction of autophagy by DHA may be mediated by inhibiting the mTOR pathway and promoting reactive oxygen species production.

Skin cancer risk and shade: comparing the risk of foresters with other outdoor workers

BACKGROUND

Keratinocyte carcinoma (KC) is an increasingly important public health problem with an especially high prevalence in outdoor workers. In contrast to other occupations, foresters spend most of their outdoor time under the shade of trees.

OBJECTIVES

We aimed to compare the unique sun exposure patterns and sun protection behaviour of foresters with those of other outdoor workers and their relation to the KC risk.

METHODS

In July 2018, a cross-sectional study was conducted at an international forestry fair using a questionnaire about health awareness and skin cancer screening by dermatologists to assess the prevalence of KC.

RESULTS

A total of 591 participants (78.7% male; mean age 46.8 ± 16.2 years) including 193 foresters were enrolled. Of all foresters, 72% experienced sunburns (solar erythema) within the past year and 50% of them experienced the worst sunburn during work. Foresters were most likely to often/always wear protective clothes (29.0%) but were least likely to often/always avoid midday sun (23.8%) and stay in the shade (31.1%). Having an outdoor profession or spending hours outside for leisure was negatively associated with sun protection. Skin examination revealed an overall KC prevalence of 16.7%, with 16.5% of foresters being affected.

CONCLUSION

Despite being protected by trees, the risk of KC for foresters is comparable to that of other professional groups. Shade alone may not provide sufficient protection. Additional sun protection measures are necessary.

[Primary and secondary prevention of skin cancer in rural areas : A cross-sectional study in the Bavarian Forest]

BACKGROUND

Skin cancer is the most common malignancy of the fair-skinned population worldwide. To reduce skin cancer's burden primary and secondary prevention are critical. However, various studies indicate an inadequate prevention behavior among rural populations.

OBJECTIVE

To examine the risk and prevention behavior with respect to skin cancer and to identify subgroups in rural areas with specific need for prevention efforts.

MATERIALS AND METHODS

In a cross-sectional study carried out in the first quarter of 2017, patients and their accompanying persons (≥18 years) were interviewed on the subject of primary and secondary prevention in waiting rooms of nondermatological medical practices in the Bavarian Forest, Germany. Data were collected using paper-based questionnaires. Associations were calculated using logistic regression models.

RESULTS

In all, 880 persons (57.7% women, mean age = 49.5 years) were included in the analysis, of whom 53.6% had undergone a skin cancer screening at least once before. Sunscreen was the most frequently used sun protection measure. Male sex and being 18-34 years of age were significantly associated with not using prevention measures (depending on the measure: odds ratio [OR]: 1.4-2.4 and 1.8-3.7, respectively). In addition, not using skin cancer screening was associated with UV exposure more than 6 h daily in summer (OR: 1.8, 95%-CI [confidence interval]: 1.14-2.97).

CONCLUSION

Future prevention strategies should increasingly focus on young adults, on men and people with high solar UV exposition particularly, to reduce the burden of skin cancer in rural areas.

Happiness in dermatology: a holistic evaluation of the mental burden of skin diseases

BACKGROUND

According to the World Health Organization, mental health is a state of well-being and not merely the absence of disease. However, studies exploring subjective well-being in patients with skin diseases are very rare.

OBJECTIVES

To assess subjective well-being, i.e. 'happiness', in patients with different skin diseases and to compare them to other patient groups and healthy controls.

METHODS

A cross-sectional study was conducted from 12/2017 to 04/2019. Patients receiving in- or outpatient care for psoriasis, atopic eczema, nummular eczema, mastocytosis, skin cancer (malignant melanoma and keratinocyte carcinoma), human immunodeficiency virus (HIV) or chronic inflammatory bowel diseases (Crohn's disease and ulcerative colitis) were recruited at two hospitals in Bavaria, Germany. Healthy individuals living in or near Munich served as a control group. All participants filled in a questionnaire assessing happiness, measured as positive affect (PA), negative affect and satisfaction with life (SWL; together representing subjective well-being) and a heuristic evaluation of one's own happiness.

RESULTS

Data from 229 dermatologic patients (53.3 ± 18.5 years, 48% women), 49 patients with inflammatory bowel diseases (48.9 ± 18.7 years, 43% women), 49 patients with HIV (46 ± 10.1 years, 10% women) and 106 healthy controls (38.4 ± 13.4 years, 49% women) were analysed. Compared to the controls, dermatologic patients reported lower heuristic happiness (P = 0.023) and PA (P = 0.001) but higher SWL (P = 0.043). Patients with psoriasis and atopic eczema reported the lowest happiness, as they reported significantly lower PA (P = 0.032 and P < 0.001) and heuristic happiness (P = 0.002 and P = 0.015) than the control group. Patients with skin cancer reported higher SWL than the control group (P = 0.003). Dermatologic patients reported lower happiness than patients with HIV but reported greater happiness than patients with IBD.

CONCLUSIONS

Dermatologic patients experience lower levels of happiness, especially PA, compared to healthy controls. As PA is linked to desirable health outcomes, targeting PA could be a promising holistic approach for the treatment of skin diseases.