The Robust Tumoricidal Effects of Combined BET/HDAC Inhibition in Cutaneous T-Cell Lymphoma Can Be Reproduced by ΔNp73 Depletion.

Combined BET inhibitor/histone deacetylase inhibitor treatment induces marked apoptosis of cutaneous T-cell lymphoma (CTCL) with minimal normal T-cell toxicity. At 96 hours when apoptosis was extensive, a majority of CTCL lines showed ≥2-fold suppression of T-cell survival factors (e.g., AKT1, BCL2 antiapoptotic factors, BIRC5, CD40, CD70, GADD45A, PRKCA, TNFRSF1B, ΔNp73) and ≥2-fold upregulation of proapoptotic factors and tumor suppressors (e.g., ATM, BAK, BIM, multiple caspases, FHIT, HIC1, MGMT, NOD1) (P < 0.05). The largest alterations were in TP73 isoform expression, resulting in increased TAp73/ΔNp73 ratios in CTCL lines and leukemic Sézary cells. Targeted ΔNp73 inhibition by small interfering RNA knockdown resulted in robust CTCL apoptosis comparable with that induced by BET inhibitor/histone deacetylase inhibitor with minimal normal T-cell toxicity. Chromatin immunoprecipitation analysis showed that BET inhibitor/histone deacetylase inhibitor treatment reduced RNA polymerase II binding to ΔNp73, MYC, and AKT1 while increasing its binding to TAp73. CTCL skin lesions expressed both TAp73 and ΔNp73 isoforms in situ. In aggregate, these findings implicate TAp73/ΔNp73 balance as a major factor governing CTCL survival, show that the expression of p73 isoforms can be altered by molecular biological and pharmaceutical means, show that p73 isoforms are expressed across the entire CTCL clinical spectrum, and identify the p73 pathway as a potential target for therapeutics.

Management of Mycosis Fungoides with Topical Chlormethine/Mechlorethamine Gel: A Columbia University Cutaneous Lymphoma Center Experience.

Mycosis fungoides is a type of cutaneous T-cell lymphoma, which accounts for the majority of cases of cutaneous T-cell lymphoma. Mycosis fungoides can be classified as early-stage (IA-IIA) or late-stage (IIB or greater) disease. In early-stage mycosis fungoides, skin-directed therapies are commonly used to manage the disease. Chlormethine, or mechlorethamine, is a topical chemotherapeutic, which has been in use for over 60 years. In 2013, the US Food and Drug Administration approved chlormethine/mechlorethamine gel (Valchlor®) for treatment of stage IA and IB mycosis fungoides. Chlormethine/mechlorethamine gel is an effective therapy; however, its use may be limited by the development of adverse cutaneous reactions. Off-label dosing modifications, as well as co-administration of topical steroids and an aggressive moisturization regimen, can be used to reduce these side-effects. We report here 4 cases of mycosis fungoides treated with chlormethine/mechlorethamine gel at the Comprehensive Skin Cancer Center at Columbia University Irving Medical Center, which provide insights into the use of this therapy in clinical practice.

Immune Checkpoint Inhibition in Non-Melanoma Skin Cancer: A Review of Current Evidence.

Immuno-oncology is a rapidly evolving field with growing relevance in the treatment of numerous malignancies. The prior study of immunotherapy in dermatologic oncology has largely focused on cutaneous melanoma. However, recent focus has shifted to the use of immunotherapy to treat non-melanoma skin cancers (NMSCs), such as basal cell carcinoma (BCC), cutaneous squamous cell carcinoma (cSCC), and Merkel cell carcinoma (MCC). NMSCs represent the most ubiquitous cancers globally and, while they have a lower propensity to develop into advanced disease than cutaneous melanoma, their absolute mortality burden has recently surpassed that of melanoma. Patients with advanced NMSC are now benefiting from the successes of immunotherapy, including checkpoint inhibition with anti-CTLA-4 and anti-PD-1 monoclonal antibodies. In this review, we discuss the existing clinical evidence for immunotherapy in the treatment of NMSCs, with an emphasis on checkpoint inhibitor therapies. We highlight key studies in the field and provide up-to-date clinical evidence regarding ongoing clinical trials, as well as future study directions. Our review demonstrates that checkpoint inhibitors are positioned to provide unparalleled results in the previously challenging landscape of advanced NMSC treatment.