Germline ATM variants predispose to melanoma: a joint analysis across the GenoMEL and MelaNostrum consortia

PURPOSE

Ataxia-Telangiectasia Mutated (ATM) has been implicated in the risk of several cancers, but establishing a causal relationship is often challenging. Although ATM single-nucleotide polymorphisms have been linked to melanoma, few functional alleles have been identified. Therefore, ATM impact on melanoma predisposition is unclear.

METHODS

From 22 American, Australian, and European sites, we collected 2,104 familial, multiple primary (MPM), and sporadic melanoma cases who underwent ATM genotyping via panel, exome, or genome sequencing, and compared the allele frequency (AF) of selected ATM variants classified as loss-of-function (LOF) and variants of uncertain significance (VUS) between this cohort and the gnomAD non-Finnish European (NFE) data set.

RESULTS

LOF variants were more represented in our study cohort than in gnomAD NFE, both in all (AF = 0.005 and 0.002, OR = 2.6, 95% CI = 1.56-4.11, p < 0.01), and familial + MPM cases (AF = 0.0054 and 0.002, OR = 2.97, p < 0.01). Similarly, VUS were enriched in all (AF = 0.046 and 0.033, OR = 1.41, 95% CI = 1.6-5.09, p < 0.01) and familial + MPM cases (AF = 0.053 and 0.033, OR = 1.63, p < 0.01). In a case-control comparison of two centers that provided 1,446 controls, LOF and VUS were enriched in familial + MPM cases (p = 0.027, p = 0.018).

CONCLUSION

This study, describing the largest multicenter melanoma cohort investigated for ATM germline variants, supports the role of ATM as a melanoma predisposition gene, with LOF variants suggesting a moderate-risk.

Follicular and epidermal alterations in patients treated with ZD1839 (Iressa), an inhibitor of the epidermal growth factor receptor

We report the cutaneous side-effects of ZD1839 (Iressa), a new anticancer agent that acts by inhibiting epidermal growth factor (EGF) receptor signal transduction. Three patients receiving ZD1839 developed an eruption consisting of follicular papules and pustules in an acneiform distribution as well as diffuse fine scaling of the skin. Additionally, hair growth abnormalities were noted in two patients. Histologically, a superficial purulent folliculitis and disordered differentiation with focal parakeratosis were seen. The follicular eruption appeared to respond favourably to treatment with tretinoin cream and minocycline. The cutaneous adverse effects of ZD1839 are similar to those of other EGF receptor-targeted agents and result from direct interference with the functions of EGF receptor signalling in the skin.

Isolation and partial characterization of a novel subset of human T lymphocytes defined by monoclonal antibodies

A novel subset of human blood lymphocytes was isolated by means of labelling with monoclonal antibodies and fluorescence-activated cell sorting. In normal individuals, the new subset accounts for about 2% of the blood T lymphocytes. The cells of this subset bind monoclonal antibodies specific for T lymphocytes in general [e.g. OKT3, Hu-Lyt 3(9 . 6) and Leu-22] and they also form E rosettes. However, no binding is seen with monoclonal antibodies to T-lymphocyte subsets (OKT4, OKT8, Leu-2A and Leu-3A). Moreover, the lymphocytes of this new subset express neither Ia antigens nor membrane immunoglobulins. They do not bind OKM1, an antibody against cells of the myelomonocytic lineage that also reacts with natural killer cells, nor do they bind OKT6 or OKT10, specific for thymocyte antigens. The cells have a high specific gravity, a thymocyte-like pattern of lactate dehydrogenase isoenzymes and do not contain terminal deoxynucleotidyl transferase. Although these lymphocytes are viable, also after culture in vitro, and can be stored in liquid nitrogen, they are inert in all functional systems tested: they neither proliferate upon stimulation with mitogens or allogeneic cells, nor do they display suppressor or natural killer cell activity. A patient who was successfully reconstituted by bone marrow transplantation for severe combined immunodeficiency, was found to contain an abnormally high (25%--30%) fraction of these OKT3 positive, OKT4 and OKT8 negative cells among his circulating T lymphocytes.

Changes in human T lymphocytes after thymectomy and during senescence

Peripheral lymphocytes from individuals who had been thymectomized in adult life for myasthenia gravis (MG) or for other, nonimmunological reasons showed a moderate decrease in proliferative response capacity to several T-cell mitogens as compared to lymphocytes from normal individuals. The decrease of the response to mitogens and allogeneic lymphocytes was 20-30% within 5 years after thymectomy and about 50% more than 15 years after thymectomy. A comparable decrease in lymphocyte proliferative response capacity was found in healthy aged humans (68-97 years old). Analysis of T lymphocytes from both aged and thymectomized individuals with monoclonal (OKT) antibodies showed a similar pattern: the proportion of T lymphocytes binding OKT6, OKT10, or OKI1 were found. A biochemical parameter for human T-cell differentiation, the lactate dehydrogenase (LDH) isoenzyme pattern, showed a significantly lower H/M ratio in the group of elderly people compared to young individuals. Furthermore, among patients thymectomized for MG, a significant correlation was observed between the LDH isoenzyme pattern of the T lymphocytes and the proliferative response to mitogens of these cells. In contrast, in healthy thymectomized individuals the LDH isoenzyme pattern appeared to be normal. These findings indicate that, after thymectomy or involution of the thymus, at least part of the peripheral blood T lymphocytes have properties different from those of the cells of young individuals. These cells might represent immature and/or not fully differentiated lymphocytes.

Studies on the metabolic activation of benzidine by isolated rat hepatocytes

Isolated rat liver cells were shown to metabolize the aromatic amine benzidine to reactive products which are mutagenic to Salmonella typhimurium TA 1538 and which give rise to DNA excision repair within the liver cells. Intact rat liver cells are shown to be more active in the formation of mutagenic metabolites than the 9000-g supernatant from these cells. Data are presented which are in favour of the role of N-acetylation in this respect. Furthermore, indications are presented that a sulfation reaction is involved in the generation of DNA modifying metabolites, whereas formation of mutagenic products is likely to proceed via deacetylation and/or N,O-acyltransfer. Finally, data are given about the extrahepatocellular appearance of premutagenic metabolites which are more prone to metabolic activation by additional metabolic factors in the Salmonella assay than benzidine itself. The impact of these observations on the estimation of the genotoxic potential of benzidine will be discussed.

Reactivity differences among human T cells from blood and lymphoid organs, analysed by limiting dilution: correlation with specific gravity and binding of peanut lectin

Human T cells from peripheral blood, cord blood, thymus, spleen and lymph node were analysed for their proliferative response capacity to mitogens, for their specific gravity and size, and for their binding capacity of peanut agglutinin. A close correlation was found between these parameters: thymocytes and T cells from spleen were consistently heavier and smaller, and showed a lower proliferative response capacity, than T cells from blood or lymph node. Similarly, within each cell population, the small, heavy cells were least reactive. The limiting-dilution analysis revealed that heavy T cells from peripheral blood contain a lower number of reactive cells than the light peripheral T lymphocytes. Because heavy T cells from the thymus bound more peanut lectin than did light cells, it is speculated that the differences between T cells of high and low specific gravity might reflect differences in maturation level.