Theranostic biomarkers and PARP-inhibitors effectiveness in patients with non-BRCA associated homologous recombination deficient tumors: Still looking through a dirty glass window?

: Breast cancer susceptibility gene 1 (BRCA1) and breast cancer susceptibility gene 2 (BRCA2) deleterious variants were the first and, still today, the main biomarkers of poly(ADP)ribose polymerase (PARP)-inhibitors (PARPis) benefit. The recent, increased, numbers of individuals referred for counseling and multigene panel testing, and the remarkable expansion of approved PARPis, not restricted to BRCA1/BRCA2-Pathogenic Variants (PVs), produced a strong clinical need for non-BRCA biomarkers. Significant limitations of the current testing and assays exist. The different approaches that identify the causes of Homologous Recombination Deficiency (HRD), such as the germline and somatic Homologous Recombination Repair (HRR) gene PVs, the testing showing its consequences, such as the genomic scars, or the novel functional assays such as the RAD51 foci testing, are not interchangeable, and should not be considered as substitutes for each other in clinical practice for guiding use of PARPi in non-BRCA, HRD-associated tumors. Today, the deeper knowledge on the significant relationship among all proteins involved in the HRR, not limited to BRCA, expands the possibility of a successful non-BRCA, HRD-PARPi synthetic lethality and, at the same time, reinforces the need for enhanced definition of HRD biomarkers predicting the magnitude of PARPi benefit

BRCA-associated hereditary male cancers: can gender affect the prevalence and spectrum of germline pathogenic variants?

IntroductionAlthough hereditary male neoplasms are quite rare, individuals harbouring germline BRCA1/2 pathogenic variants (PVs) may have a risk of developing tumours associated with Hereditary Breast and Ovarian Cancer (HBOC) syndrome, including male breast (MBC), prostate (PCa) and pancreatic (PC) cancers, and melanoma. Women and men showed a comparable genetic architecture of cancer susceptibility, but there are some gender-specific features. Since little is known about cancer genetic susceptibility in male population, our study was aimed at investigating the frequency of BRCA1/2 PVs in men with HBOC syndrome-associated tumors, in order to understand whether differences in gender may reflect in the prevalence and spectrum of germline alterations.Patients and methodsWe retrospectively collected and analysed clinical information of 352 HBOC-associated male cancer patients genetically tested for germline BRCA1/2 PVs by Next-Generation Sequencing analysis, enrolled, from February 2018 to January 2024, at the “Regional Center for the prevention, diagnosis and treatment of rare and heredo-familial tumors of adults” of the University-Hospital Policlinico “P. Giaccone” of Palermo (Italy).ResultsOur investigation revealed that 7.4% of patients was carrier of a germline BRCA PV, with an almost total prevalence of BRCA2 alterations. In particular, 65.4% of BRCA-positive patients developed MBC, 19.2% had PC, 11.6% developed PCa, and only 3.8% had melanoma. Specifically, MBC individuals showed a BRCA-associated genetic predisposition in 17% of cases, whereas patients with PCa or PC exhibited a lower frequency of BRCA2 PVs, taking into account the current national criteria for access to germline genetic testing.DiscussionOur study showed a high heterogeneity in prevalence of germline BRCA2 PVs among men which could reflect a potential gender-specific genetic heterogeneity. Therefore, BRCA-associated male tumours could be due to BRCA2 PVs different from those usually detected in women. In the event that it is demonstrated, in future, that male cancers are genetically distinct entities from those female this could improve personalized risk evaluation and guide therapeutic choices for patients of both sexes, in order to obtain a gender equality in cancer care

CHARACTERIZATION OF TRANSFORMED CELL LINES OBTAINED FROM PRIMARY RAT CORTICAL ASTROCYTES

Brain cancers are complex and heterogeneous; most of them derive from glial cells[1], and are called gliomas, further subdivided into astrocytomas, oligodendrogliomas, ependymomas and glioastrocytomas[2]. The malignant cells undergo modifications of their metabolism and behaviour, and acquire the ability to migrate along the blood vessels in small groups (model of the guerrilla war)[3], thus invading the surrounding brain parenchyma. Most important, they have the capacity to affect the surrounding microenvironment, by altering both the extracellular matrix and the properties of the normal cells present in the brain, including glial-, endothelial-, and immune-cells, further promoting cancer cell growth and migration. Most of these effects are probably due to molecules (nucleic acids, proteins, lipids etc.) released from cancer cells into their environment via extracellular vesicles (EVs)[1]. Although a lot of efforts have been done, over the years, in order to acquire a better understanding of gliomas at the molecular level, and to set combined therapeutic approaches, brain cancers are mostly incurable. In order to gain a better knowledge of the cellular and molecular events that accompany their transformation, we started from primary cultures of rat cortical astrocytes, and selected three clones that showed increasingly high cell division rates. Then we analyzed both normal cells and their clones at the cytogenetic, cytogenomic and epigenetic level, and found that the most modified astrocytes (A-FC6 clone) have epigenetic and chromosomal alterations typical of cancer, such as an isochromosome (i8q) and that the other two clones (A-GS1 and A-VV5) have intermediate properties. We also analyzed the expression of the linker histone H1.0, normally expressed in differentiated cells[4]. Surprisingly, we found that the somatic histone H1.0 steadily increases from normal astrocytes to the A-FC6 clone. These results suggested that the normal cell cultures together with their three clones may constitute a potential model for studying glioma development. We are now analyzing the expression of other proteins normally expressed in higher amount in cancer cells (e.g. PDI and FABP7), and we are studying how much different is the ability of transformed cells to release EVs respect to normal astrocytes. One of the aim of this study is also to identify proteins and RNAs specifically sorted to EVs from both normal and transformed astrocytes