Concurrent development of high-stage cutaneous squamous cell carcinoma during complete response of metastatic cutaneous squamous cell carcinoma to programmed cell death protein 1 blockade with cemiplimab

Type 2 immunity to the rescue: enhancing antitumor immunity for skin cancer prevention

Cutaneous squamous cell carcinoma (cSCC) incidence and deaths continue to rise, underscoring the need for improved cSCC prevention. Elimination of actinic keratosis (AK) precursor lesions is a major strategy to prevent cSCC. Topical calcipotriol and 5-fluorouracil (5-FU) have been shown to eliminate AKs and reduce the risk of cSCC development, but the mechanism was undefined. In this issue of the JCI, Oka et al. demonstrate that type 2 immunity is necessary and sufficient for the elimination of premalignant keratinocytes and cSCC prevention. Paired biopsies from AK lesions and unaffected skin revealed that only keratinocytes from AKs produced thymic stromal lymphopoietin (TSLP) and damage-associated molecular patterns, resulting in selective recruitment of Th2 cells to the AK lesion. In mouse models of skin carcinogenesis, TSLP was necessary to recruit Th2 cells and trigger IL-24-mediated keratinocyte cell death. These findings suggest that the TSLP/Th2/IL-24 axis is a potential therapeutic target for SCC prevention.

Immune Checkpoints and Cellular Landscape of the Tumor Microenvironment in Non-Melanoma Skin Cancer (NMSC)

Non-melanoma skin cancer (NMSC) is primarily categorized into basal cell carcinoma (BCC), the most prevalent form of skin cancer, and cutaneous squamous cell carcinoma (cSCC), the second most common type. Both BCC and cSCC represent a significant health burden, particularly in immunocompromised individuals and the elderly. The immune system plays a pivotal role in the development and progression of NMSC, making it a critical focus for therapeutic interventions. This review highlights key immunological targets in BCC and cSCC, with a focus on immune checkpoint molecules such as PD-1/PD-L1 and CTLA-4, which regulate T cell activity and contribute to immune evasion. This review also highlights anti-tumor immune cell subsets within the tumor microenvironment (TME), such as tumor-infiltrating lymphocytes (TILs) and dendritic cells. Additionally, it examines the immunosuppressive elements of the TME, including regulatory T cells (Tregs), myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), and cancer-associated fibroblasts (CAFs), as well as their roles in NMSC progression and resistance to therapy. Emerging strategies targeting these immune elements, such as monoclonal antibodies, are also discussed for their potential to enhance anti-tumor immune responses and improve clinical outcomes. By elucidating the immunological landscape of BCC and cSCC and drawing comparisons to melanoma, this review highlights the transformative potential of immunotherapy in treating these malignancies.

Cemiplimab for metastatic squamous cell carcinoma of the orbit, periocular adnexa, and thigh

The current case presentation highlights the potential of cemiplimab, a programmed cell death protein-1 (PD-1) inhibitor, as first-line treatment for periocular metastatic cutaneous squamous cell carcinoma (SCC) without requiring curative surgery or radiotherapy. A 64-year-old male presented with a progressing 4.5 × 3.0 cm left upper eyelid lesion initially diagnosed as psoriasis. Work-up revealed cutaneous SCC with tumor invasion into extraconal fat and lacrimal gland, and metastasis to the left parotid lymph node. The patient also presented with a suspicious lesion on his left medial thigh found to be a second primary on pathology. To avoid orbital exenteration and treat the multifocal disease, the patient was started on intravenous cemiplimab immunotherapy. Following six doses, repeated FGD-PET-CT revealed a complete response of the left eyelid lesion and residual low-grade hypermetabolic activity of the left medial thigh lesion. Biopsy confirmed chronic inflammation and fibrosis with no signs of malignancy. This unique case with dual primary cutaneous SCC provides support for cemiplimab in treating locally invasive periocular SCC, and potentially abrogating the need for highly morbid exenteration procedures to preserve binocular vision.

Review: PD-L1 as an emerging target in the treatment and prevention of keratinocytic skin cancer

Recent advances in the understanding and targeting of immune checkpoints have led to great progress in immune therapies against many forms of cancer. While many types of immune checkpoints are currently targeted in the clinic, this review will focus on recent research implicating the programmed cell death protein 1/programmed death-ligand 1 (PD-1/PD-L1) axis as an emerging focus for the treatment of keratinocytic tumors. PD-L1 is of particular interest in nonmelanoma skin cancer (NMSC), as it is not only upregulated in these tumors but is stimulated by environmental ultraviolet exposure. This response may also make PD-L1 an excellent target for photochemoprevention using topically applied small molecule inhibitors. Here, we summarize recent investigations on PD-L1 expression and clinically relevant immune checkpoint inhibitor treatment in cutaneous squamous cell carcinoma, basal cell carcinoma, and head and neck squamous cell carcinoma, as well as small molecule agents targeting PD-L1 that may be useful for clinical development aiming at treatment or prevention of NMSC.