The interest in therapeutic cancer vaccines has caught enormous attention in recent years due to several breakthroughs in cancer research, among which the finding that successful checkpoint blockade treatments reinvigorate neo-antigen-specific T cells and that successful adoptive cell therapies are directed towards neo-antigens. Neo-antigens are cancer-specific antigens, which develop from somatic mutations in the cancer cell genome that can be highly immunogenic and are not subjected to central tolerance. As the majority of neo-antigens are unique to each patient’s cancer, a vaccine technology that is flexible and potent is required to develop personalized neo-antigen vaccines. In vitro transcribed mRNA is such a technology platform and has been evaluated for delivery of neo-antigens to professional antigen-presenting cells both ex vivo and in vivo. In addition, strategies that support the activity of T cells in the tumor microenvironment have been developed. These represent a unique opportunity to ensure durable T cell activity upon vaccination. Here, we comprehensively review recent progress in mRNA-based neo-antigen vaccines, summarizing critical milestones that made it possible to bring the promise of therapeutic cancer vaccines within reach.

Background In the majority of familial breast cancer (BC) families, the etiology of the disease remains unresolved. To identify missing BC heritability resulting from relatively rare variants (minor allele frequency ≤ 1%), we have performed whole exome sequencing followed by variant analysis in a virtual panel of 492 cancer-associated genes on BC patients from BRCA1 and BRCA2 negative families with elevated BC risk. Methods BC patients from 54 BRCA1 and BRCA2 -negative families with elevated BC risk and 120 matched controls were considered for germline DNA whole exome sequencing. Rare variants identified in the exome and in a virtual panel of cancer-associated genes [492 genes associated with different types of (hereditary) cancer] were compared between BC patients and controls. Nonsense, frame-shift indels and splice-site variants (strong protein-damaging variants, called PDAVs later on) observed in BC patients within the genes of the panel, which we estimated to possess the highest probability to predispose to BC, were further validated using an alternative sequencing procedure. Results Exome- and cancer-associated gene panel-wide variant analysis show that there is no significant difference in the average number of rare variants found in BC patients compared to controls. However, the genes in the cancer-associated gene panel with nonsense variants were more than two-fold over-represented in women with BC and commonly involved in the DNA double-strand break repair process. Approximately 44% (24 of 54) of BC patients harbored 31 PDAVs, of which 11 were novel. These variants were found in genes associated with known or suspected BC predisposition ( PALB2, BARD1, CHEK2, RAD51C and FANCA ) or in predisposing genes linked to other cancer types but not well-studied in the context of familial BC ( EXO1, RECQL4, CCNH, MUS81, TDP1, DCLRE1A, DCLRE1C, PDE11A and RINT1 ) and genes associated with different hereditary syndromes but not yet clearly associated with familial cancer syndromes ( ABCC11, BBS10, CD96, CYP1A1, DHCR7, DNAH11, ESCO2, FLT4, HPS6, MYH8, NME8 and TTC8 ). Exome-wide, only a few genes appeared to be enriched for PDAVs in the familial BC patients compared to controls. Conclusions We have identified a series of novel candidate BC predisposition variants/genes. These variants/genes should be further investigated in larger cohorts/case-control studies. Other studies including co-segregation analyses in affected families, locus-specific loss of heterozygosity and functional studies should shed further light on their relevance for BC risk. Electronic supplementary material The online version of this article (10.1186...

Lung cancer is the number one cause of cancer‐related death worldwide with cigarette smoking as its major risk factor. Although the incidence of lung cancer in never smokers is rising, this subgroup of patients is underrepresented in genomic studies of lung cancer. Here, we assembled a prospective cohort of 46 never‐smoking, nonsmall cell lung cancer (NSCLC) patients and performed whole‐exome and low‐coverage whole‐genome sequencing on tumors and matched germline DNA. We observed fewer somatic mutations, genomic breakpoints and a smaller fraction of the genome with chromosomal instability in lung tumors from never smokers compared to smokers. The lower number of mutations, enabled us to identify TSC22D1 as a potential driver gene in NSCLC. On the other hand, the frequency of mutations in actionable genes such as EGFR and ERBB2 and of amplifications in MET were higher, while the mutation rate of TP53, which is a negative prognostic factor, was lower in never smokers compared to smokers. Together, these observations suggest a more favorable prognosis for never smokers with NSCLC. Classification of somatic mutations into six‐substitution type patterns or into 96‐substitution type signatures revealed distinct clusters between smokers and never smokers. Particularly, we identified in never smokers signatures related to aging, homologous recombination damage and APOBEC/AID activity as the most important underlying processes of NSCLC. This further indicates that second‐hand smoking is not driving NSCLC pathogenesis in never smokers.

Two out of 41 non-small cell lung cancer patients enrolled in a clinical study were found with a somatic CRAF mutation in their tumor, namely CRAFP261A and CRAFP207S. To our knowledge, both mutations are novel in lung cancer and CRAFP261A has not been previously reported in cancer. Expression of CRAFP261A in HEK293T cells and BEAS-2B lung epithelial cells led to increased ERK pathway activation in a dimer-dependent manner, accompanied with loss of CRAF phosphorylation at the negative regulatory S259 residue. Moreover, stable expression of CRAFP261A in mouse embryonic fibroblasts and BEAS-2B cells led to anchorage-independent growth. Consistent with a previous report, we could not observe a gain-of-function with CRAFP207S. Type II but not type I RAF inhibitors suppressed the CRAFP261A-induced ERK pathway activity in BEAS-2B cells, and combinatorial treatment with type II RAF inhibitors and a MEK inhibitor led to a stronger ERK pathway inhibition and growth arrest. Our findings suggest that the acquisition of a CRAFP261A mutation can provide oncogenic properties to cells, and that such cells are sensitive to combined MEK and type II RAF inhibitors. CRAF mutations should be diagnostically and therapeutically explored in lung and perhaps other cancers.

Somatic mutations in the epidermal growth factor receptor-tyrosine kinase (EGFR-TK) domain of non-small cell lung cancer (NSCLC) influence the responsiveness of these tumors to EGFR-TK inhibitors, indicating their usefulness as a predictive molecular marker. However, for mutation analysis, the amount of clinical material available from NSCLC patients is often very limited, suboptimally preserved, and composed of both normal and tumor cells. As a consequence, the total amount of recovered DNA is frequently very limited, with mutant alleles being often strongly underrepresented, and thus requiring highly sensitive methods for the detection of mutations. In the present study, EGFR mutation screening was performed on 210 NSCLC clinical samples by heminested polymerase chain reaction (PCR), followed by denaturing gradient gel electrophoresis (DGGE). Candidate mutations were further characterized by sequencing. Seventeen different types of pathogenic EGFR-TK domain mutations were detected in 55 of the 210 samples (26%). We reanalyzed 149 of the 155 samples in which no mutation was found by real-time PCR for the presence of recurrent exon 21 and exon 19 mutations using peptide nucleic acid probes in the PCR mix to increase sensitivity by mutant allele enrichment. Four additional samples with exon 19 mutations were detected. Thus, it is found that the relatively simple and inexpensive PCR-DGGE assay is already very sensitive for the detection of mutations in clinical samples, including samples with low tumor cellularity (10% or higher tumor cell content), although the sensitivity and speed of the assay can be further increased for a restricted panel of mutations by introducing peptide nucleic acid probes in the DGGE or real-time PCR-based assay.

e23197 Background: During the Belgian FIELT II clinical study, two non-small cell lung cancers among 41 were found to harbor a CRAF mutation. One of these mutations (P207S) was previously found in fibrosarcoma and characterized as not activating the ERK pathway at higher levels compared to the wild-type CRAF. The other mutation (P261A) has never been reported in cancer but found in Noonan syndrome. CRAF mutations can be oncogenic thereby activation of the ERK pathway. Serine 259 is a negative regulatory site and its phosphorylation is essential for keeping the CRAF auto-inhibited. P261A CRAF prevents phosphorylation of S259 but its role in cancer and its possible response to small molecule inhibitors has yet to be uncovered. Methods: We generated recombinant CRAF expression vectors by site-directed mutagenesis and investigated the ERK pathway activation status induced by CRAF mutants, in HEK293T cells and BEAS-2B (lung epithelial) cells. We tested the effect of candidate inhibitors at a clinically relevant dose on ERK pathway activity in BEAS-2B cells expressing CRAF mutants. Results: Expression of P261A CRAF in both HEK293T and BEAS-2B cells leads to increased ERK pathway activation compared to wtCRAF, accompanied by decreased phosphorylation of S259. P207S CRAF induces ERK pathway activity at levels comparable to wtCRAF and we observed that co-expression of BRAF with P207S CRAF does not lead to increased ERK activity compared to wtCRAF/BRAF. RAF-inhibitors LY3009120 and AZD-628 suppress ERK pathway activity induced by P261A CRAF in BEAS-2B cells. LY3009120 showed stronger ERK-inhibitory effect compared to AZD-628. In contrast, Dabrafenib (RAF-inhibitor) treatment of mutant or wtCRAF expressing cells leads to paradoxical ERK activation. Combinatorial treatment of LY3009120 with Trametinib (MEK-inhibitor) leads to stronger ERK-inhibitory effects compared to either single agent treatment in cells expressing mutant CRAF. Conclusions: The P261A CRAF mutation is ERK pathway activating and predicts sensitivity to LY3009120 and Trametinib. CRAF inhibition should be clinically explored in lung cancers and perhaps other cancers with sensitizing CRAF mutations.