No abstract

The rare benign giant cell tumour of bone (GCTB) is defined by an almost unique mutation in the H3.3 family of histone genes H3-3A or H3-3B; however, the same mutation is occasionally found in primary malignant bone tumours which share many features with the benign variant. Moreover, lung metastases can occur despite the absence of malignant histological features in either the primary or metastatic lesions. Herein we investigated the genetic events of 17 GCTBs including benign and malignant variants and the methylation profiles of 122 bone tumour samples including GCTBs. Benign GCTBs possessed few somatic alterations and no other known drivers besides the H3.3 mutation, whereas all malignant tumours harboured at least one additional driver mutation and exhibited genomic features resembling osteosarcomas, including high mutational burden, additional driver event(s), and a high degree of aneuploidy. The H3.3 mutation was found to predate the development of aneuploidy. In contrast to osteosarcomas, malignant H3.3-mutated tumours were enriched for a variety of alterations involving TERT, other than amplification, suggesting telomere dysfunction in the transformation of benign to malignant GCTB. DNA sequencing of the benign metastasising GCTB revealed no additional driver alterations; polyclonal seeding in the lung was identified, implying that the metastatic lesions represent an embolic event. Unsupervised clustering of DNA methylation profiles revealed that malignant H3.3-mutated tumours are distinct from their benign counterpart, and other bone tumours. Differential methylation analysis identified CCND1, encoding cyclin D1, as a plausible cancer driver gene in these tumours because hypermethylation of the CCND1 promoter was specific for GCTBs. We report here the genomic and methylation patterns underlying the rare clinical phenomena of benign metastasising and malignant transformation of GCTB and show how the combination of genomic and epigenomic findings could potentially distinguish benign from malignant GCTBs, thereby predicting aggressive behaviour in challenging diagnostic cases.

Highlights d Representative sequencing (Rep-Seq) is a new method for tumor molecular profiling d Rep-Seq homogenizes residual tumor tissue not taken for standard pathology d Representative sampling of tumors generates accurate tumor mutation burden scores d Rep-Seq detects more mutations and accurately resolves clonal from subclonal variants

A leaf protein concentrate prepared from the young leaves of the common nettle (Urtica dioica) failed to support normal growth in young rats; supplementation with methionine produced a protein efficiency ratio greater than that of casein. A nettle leaf wholemeal, providing 66% of the dietary protein, supported normal growth in young guinea-pigs, mice and rats. Chicks receiving the whole nettle meal as their sole dietary protein grew at only half the rate of chicks given a standard commercial diet. A nettle meal-induced hypercholesterolaemia in mature guinea-pigs and kidney hypertrophy in mice and guinea-pigs should perhaps be interpreted as a caution against the indiscriminate introduction of nettles into the human diet.