Colon Immune-Related Adverse Events: Anti-CTLA-4 and Anti-PD-1 Blockade Induce Distinct Immunopathological Entities.

BACKGROUND AND AIM: Immune checkpoint inhibitors targeting CTLA-4 and PD-1 improve survival in cancer patients but may induce immune-related adverse events, including colitis. The immunological characteristics of anti-CTLA-4 [αCTLA-4]- and anti-PD-1 [αPD-1]-related colitis have been poorly described. The aim of the present study was to compare the immunological and histological characteristics of αCTLA-4-induced colitis and αPD-1-induced colitis. METHODS: Colonic biopsies from patients with αCTLA-4-induced colitis, αPD-1-induced colitis, and inflammatory bowel disease [IBD] were analysed by immunohistochemistry and flow cytometry. Tumour necrosis factor alpha [TNFα] concentration was assessed in biopsy supernatants. RESULTS: CD8+ T cells were found in the lamina propria and epithelium in αPD-1-induced colitis, whereas CD4+ T cells were found in the lamina propria in αCTLA-4-induced colitis. No or low intraepithelial lymphocytes were observed in αCTLA-4-induced colitis. No difference in numbers of mucosal regulatory T cells was observed between αCTLA-4- or αPD-1-induced colitis and IBD patients. Higher numbers of activated ICOS+ conventional CD4+ T cells were observed in αCTLA-4-induced colitis compared with patients with IBD. Among ICOS+CD4+ T cells, conventional CD4+ T cells were the main T cell population in patents with αCTLA-4-induced colitis, whereas Treg cells were predominant in IBD or αPD-1-induced colitis. High mucosal TNFα concentrations were observed in αCTLA-4-induced colitis. Low mucosal TNFα concentrations were associated with steroid sensitivity. CONCLUSIONS: These observations show that αCTLA-4- and αPD-1-induced colitis have distinct immunological characteristics. Mucosal TNFα concentration might detect patients at risk of developing corticosteroid resistance after CTLA-4 blockade.

Molecular characterization and patient outcome of melanoma nodal metastases and an unknown primary site.

BACKGROUND: Melanoma of unknown primary site (MUP) is not a completely understood entity with nodal metastases as the most common first clinical manifestation. The aim of this multicentric study was to assess frequency and type of oncogenic BRAF/NRAS/KIT mutations in MUP with clinically detected nodal metastases in relation to clinicopathologic features and outcome. MATERIALS AND METHODS: We analyzed series of 103 MUP patients (period: 1992-2010) after therapeutic lymphadenectomy (LND): 40 axillary, 47 groin, 16 cervical, none treated with BRAF inhibitors. We performed molecular characterization of BRAF/NRAS/KIT mutational status in nodal metastases using direct sequencing of respective coding sequences. Median follow-up time was 53 months. RESULTS: BRAF mutations were detected in 55 cases (53 %) (51 V600E, 93 %; 4 others, 7 %), and mutually exclusive NRAS mutations were found in 14 cases (14 %) (7 p.Q61R, 4 p.Q61K, 2 p.Q61H, 1 p.Q13R). We have not detected any mutations in KIT. The 5-year overall survival (OS) was 34 %; median was 24 months. We have not found significant correlation between mutational status (BRAF/NRAS) and OS; however, for BRAF or NRAS mutated melanomas we observed significantly shorter disease-free survival (DFS) when compared with wild-type melanoma patients (p = .04; 5-year DFS, 18 vs 19 vs 31 %, respectively). The most important factor influencing OS was number of metastatic lymph nodes >1 (p = .03). CONCLUSIONS: Our large study on molecular characterization of MUP with nodal metastases showed that MUPs had molecular features similar to sporadic non-chronic-sun-damaged melanomas. BRAF/NRAS mutational status had negative impact on DFS in this group of patients. These observations might have potential implication for molecular-targeted therapy in MUPs.

RAS mutations are associated with the development of cutaneous squamous cell tumors in patients treated with RAF inhibitors.

PURPOSE: RAF inhibitors are effective against melanomas with BRAF V600E mutations but may induce keratoacanthomas (KAs) and cutaneous squamous cell carcinomas (cSCCs). The potential of these agents to promote secondary malignancies is concerning. We analyzed cSCC and KA lesions for genetic mutations in an attempt to identify an underlying mechanism for their formation. METHODS: Four international centers contributed 237 KA or cSCC tumor samples from patients receiving an RAF inhibitor (either vemurafenib or sorafenib; n = 19) or immunosuppression therapy (n = 53) or tumors that developed spontaneously (n = 165). Each sample was profiled for 396 known somatic mutations across 33 cancer-related genes by using a mass spectrometric-based genotyping platform. RESULTS: Mutations were detected in 16% of tumors (38 of 237), with five tumors harboring two mutations. Mutations in TP53, CDKN2A, HRAS, KRAS, and PIK3CA were previously described in squamous cell tumors. Mutations in MYC, FGFR3, and VHL were identified for the first time. A higher frequency of activating RAS mutations was found in tumors from patients treated with an RAF inhibitor versus populations treated with a non-RAF inhibitor (21.1% v 3.2%; P < .01), although overall mutation rates between treatment groups were similar (RAF inhibitor, 21.1%; immunosuppression, 18.9%; and spontaneous, 17.6%; P = not significant). Tumor histology (KA v cSCC), tumor site (head and neck v other), patient age (≤ 70 v > 70 years), and sex had no significant impact on mutation rate or type. CONCLUSION: Squamous cell tumors from patients treated with an RAF inhibitor have a distinct mutational profile that supports a mechanism of therapy-induced tumorigenesis in RAS-primed cells. Conceivably, cotargeting of MEK together with RAF may reduce or prevent formation of these tumors.