Targeting MEK in a Translational Model of Histiocytic Sarcoma

Abstract

Histiocytic sarcoma in humans is an aggressive orphan disease with a poor prognosis as treatment options are limited. Dogs are the only species that spontaneously develops histiocytic sarcoma with an appreciable frequency, and may have value as a translational model system. In the current study, high-throughput drug screening utilizing histiocytic sarcoma cells isolated from canine neoplasms identified these cells as particularly sensitive to a MEK inhibitor, trametinib. One of the canine cell lines carries a mutation in PTPN11 (E76K), and another one in KRAS (Q61H), which are associated with the activation of oncogenic MAPK signaling. Both mutations were previously reported in human histiocytic sarcoma. Trametinib inhibited sensitive cell lines by promoting cell apoptosis, indicated by a significant increase in caspase 3/7. Furthermore, findings were successfully recapitulated in an intrasplenic orthotopic xenograft mouse model, which represents a disseminated aggressive form of histiocytic sarcoma. Mice with histiocytic sarcoma xenograft neoplasms that were treated with trametinib had significantly longer survival times. Target engagement was validated as activity of ERK, downstream of MEK, was significantly downregulated in neoplasms of treated mice. Additionally, trametinib was found in plasma and neoplastic tissues within projected therapeutic levels. These findings demonstrate that in dogs, histiocytic sarcoma may be associated with a dysfunctional MAPK pathway, at least in some cases, and may be effectively targeted through MEK inhibition. Clinical trials to test safety and efficacy of trametinib in dogs with histiocytic sarcoma are warranted, and may provide valuable translational information to similar diseases in humans..

The MEK1/2 pathway as a therapeutic target in high-grade serous ovarian carcinoma

“…Prolonged mitotic block results in apoptosis induction and eventual cell death [62,63]. In a similar way, inhibition of MEK1/2 with trametinib induced death of various tumor cells that are heavily dependent on elevated RAS-RAF-MEK1/2-ERK1/2 cascade activity [64][65][66][67]. In contrast to these reports, we did not detect any cytotoxic effects caused by MEK1/2 inhibition in HGSOC cells.…”

Interest of circulating tumor DNA as a biomarker for canine cancers: illustration in histiocytic sarcoma, oral malignant melanoma and multicentric lymphoma

“…In the future, this test could be considered in veterinary oncology, to guide treatment procedure toward targeted therapy. Indeed, others and us showed that PTPN11 mutations were associated with the activation of the MAPK pathway, and in vitro test showed that canine HS cell lines were sensitive to MEK inhibitors 27,59,60 . As our ctDNA assay demonstrated a sensitivity of 91.3% and a specificity of 100% for the detection of PTPN11 mutation in the plasma of dogs carrying PTPN11 mutated HS, it could efficiently select dogs susceptible to benefit from this targeted therapy.…”

Activating Mutations in PTPN11 and KRAS in Canine Histiocytic Sarcomas

“…Downstream to SHP-2, MAPK and PI3K/AKT pathways are also potential targets for neoplasms with mutated PTPN11 and KRAS , and for which several FDA-approved inhibitors are currently available. We have demonstrated that trametinib, an MEK inhibitor, significantly inhibited canine HS cells by promoting cell cycle arrest and cell apoptosis [32]. Additionally, trametinib prolonged survival of mice carrying xenograft HS orthotopically (intrasplenic) [33,46].…”

“…HS cell lines derived by our laboratory from BMDs (BD and OD), a Rottweiler (PJ) and a golden retriever (DH82, obtained from ATCC (CRL-10389)) were also included in the study. A comprehensive characterization of the BD, OD and PJ cell lines has been reported by our group [32,35]. DH82 is a commercially available cell line reportedly derived from a hemophagocytic HS in a golden retriever.…”

“…Our goal in the present study was to evaluate the prevalence of mutations within the MAPK pathway in a large cohort of BMDs with HS, as well as in a cohort of BMDs with lymphoma, the second most common malignancy in this breed. In addition to the previously reported mutations PTPN11 E76K and KRAS Q61H , we now report and include in the analysis a second missense mutation, PTPN11 G503V (c.1,508G>T, p.Gly503Val), located in exon 13 of the PTP domain of SHP-2 (Figure 1A,B) [32]. These mutations have recently been identified by our group in HS cell lines that have been established in our laboratory (two originating from BMDs and one from a Rottweiler), and DH82, a commercially available cell line through ATCC, originated from a hemophagocytic HS from a golden retriever, and originally described by Wellman et al in 1998 [33] and further characterized by Heinrich et al in 2015 [34].…”