Wound healing with topical BRAF inhibitor therapy in a diabetic model suggests tissue regenerative effects

Wound healing is a multi-step process to rapidly restore the barrier function. This process is often impaired in diabetic patients resulting in chronic wounds and amputation. We previously found that paradoxical activation of the mitogen-activated protein kinase (MAPK) pathway via topical administration of the BRAF inhibitor vemurafenib accelerates wound healing by activating keratinocyte proliferation and reepithelialization pathways in healthy mice. Herein, we investigated whether this wound healing acceleration also occurs in impaired diabetic wounds and found that topical vemurafenib not only improves wound healing in a murine diabetic wound model but unexpectedly promotes hair follicle regeneration. Hair follicles expressing Sox-9 and K15 surrounded by CD34+ stroma were found in wounds of diabetic and non-diabetic mice, and their formation can be prevented by blocking downstream MEK signaling. Thus, topically applied BRAF inhibitors may accelerate wound healing, and promote the restoration of improved skin architecture in both normal and impaired wounds.

Primary Resistance to PD-1 Blockade Mediated by JAK1/2 Mutations

Loss-of-function mutations in JAK1/2 can lead to acquired resistance to anti-programmed death protein 1 (PD-1) therapy. We reasoned that they may also be involved in primary resistance to anti-PD-1 therapy. JAK1/2-inactivating mutations were noted in tumor biopsies of 1 of 23 patients with melanoma and in 1 of 16 patients with mismatch repair-deficient colon cancer treated with PD-1 blockade. Both cases had a high mutational load but did not respond to anti-PD-1 therapy. Two out of 48 human melanoma cell lines had JAK1/2 mutations, which led to a lack of PD-L1 expression upon interferon gamma exposure mediated by an inability to signal through the interferon gamma receptor pathway. JAK1/2 loss-of-function alterations in The Cancer Genome Atlas confer adverse outcomes in patients. We propose that JAK1/2 loss-of-function mutations are a genetic mechanism of lack of reactive PD-L1 expression and response to interferon gamma, leading to primary resistance to PD-1 blockade therapy.

SIGNIFICANCE

A key functional result from somatic JAK1/2 mutations in a cancer cell is the inability to respond to interferon gamma by expressing PD-L1 and many other interferon-stimulated genes. These mutations result in a genetic mechanism for the absence of reactive PD-L1 expression, and patients harboring such tumors would be unlikely to respond to PD-1 blockade therapy. Cancer Discov; 7(2); 188-201. ©2016 AACR.See related commentary by Marabelle et al., p. 128This article is highlighted in the In This Issue feature, p. 115.