Case Report: Long-Term Survival of a Patient with Cerebral Metastasized Ovarian Carcinoma Treated with a Personalized Peptide Vaccine and Anti-PD-1 Therapy

Abstract

Ovarian cancer is one of the most common cancers among women and the most lethal malignancy of all gynecological cancers. Surgery is promising in the early stages; however, most patients are first diagnosed in the advanced stages, where treatment options are limited. Here, we present a 49-year-old patient who was first diagnosed with stage III ovarian cancer. After the tumor progressed several times under guideline therapies with no more treatment options available at that time, the patient received a fully individualized neoantigen-derived peptide vaccine in the setting of an individual healing attempt. The tumor was analyzed for somatic mutations via whole exome sequencing and potential neoepitopes were vaccinated over a period of 50 months. During vaccination, the patient additionally received anti-PD-1 therapy to prevent further disease progression. Vaccine-induced T-cell responses were detected using intracellular cytokine staining. After eleven days of in vitro expansion, four T-cell activation markers (namely IFN-ɣ, TNF-α, IL-2, and CD154) were measured. The proliferation capacity of neoantigen-specific T-cells was determined using a CFSE proliferation assay. Immune monitoring revealed a very strong CD4+ T-cell response against one of the vaccinated peptides. The vaccine-induced T-cells simultaneously expressed CD154, TNF, IL-2, and IFN-ɣ and showed a strong proliferation capacity upon neoantigen stimulation. Next-generation sequencing, as well as immunohistochemical analysis, revealed a loss of Beta-2 microglobulin (B2M), which is essential for MHC class I presentation. The results presented here implicate that the application of neoantigen-derived peptide vaccines might be considered for those cancer stages, where promising therapeutic options are lacking. Furthermore, we provide more data that endorse the intensive investigation of B2M loss as a tumor escape mechanism in clinical trials using anti-cancer vaccines together with immune-checkpoint inhibitors.

Keywords: Beta-2 microglobulin; MKKS; ovarian cancer; personalized peptide vaccination.

Figure 1

Clinical course of the patient since first diagnosis (November 2010). CR = complete response; PR = partial response; SD = stable disease; PD = progressive disease.

Figure 2

Immune monitoring. (A,B) CD4+ specific T-cell response towards KQLHNGFGSY (MKKS-p.G52S) after pre-stimulation in vitro. (A) TNF-, CD154-, IL-2-, and IFN-γ-positive cells after stimulation with MKKS-p.G52S peptide (upper row) versus DMSO control (lower row). (B) Boolean gate analysis of polyfunctionality of responding CD4+ T-cells. Major populations are highlighted (C) Proliferation assay. Cells are stimulated with DMSO control, MKKS-p.G52S peptide (KQLHNGFGSY), MKKS-p.G52S peptide + anti-HLA-DR/DP/DQ mAb, MKKS-wildtype peptide (KQLHNGFGGY), or a viral peptide mix.

Figure 3

Immunohistochemistry. Expression analysis of Beta-2 microglobulin (A) and MHC II (B). Tissue 1: primary tumor (December 2010); tissue 2: spleen metastasis (February 2014); tissue 3: lymph node metastasis (September 2014); tissue 4: brain metastasis (September 2015).