Endometrial carcinosarcoma (ECS) represents one of the most extreme examples of tumor heterogeneity among human cancers. ECS is a clinically aggressive, high-grade, metaplastic carcinoma. At the morphological level, intratumor heterogeneity in ECS is due to an admixture of epithelial (carcinoma) and mesenchymal (sarcoma) components that can include heterologous tissues, such as skeletal muscle, cartilage, or bone. Most ECSs belong to the copy-number high serous-like molecular subtype of endometrial carcinoma, characterized by the TP53 mutation and the frequently accompanied by a large number of gene copy-number alterations, including the amplification of important oncogenes, such as CCNE1 and c-MYC. However, a proportion of cases (20%) probably represent the progression of tumors initially belonging to the copy-number low endometrioid-like molecular subtype (characterized by mutations in genes such as PTEN, PI3KCA, or ARID1A), after the acquisition of the TP53 mutations. Only a few ECS belong to the microsatellite-unstable hypermutated molecular type and the POLE-mutated, ultramutated molecular type. A common characteristic of all ECSs is the modulation of genes involved in the epithelial to mesenchymal process. Thus, the acquisition of a mesenchymal phenotype is associated with a switch from E- to N-cadherin, the up-regulation of transcriptional repressors of E-cadherin, such as Snail Family Transcriptional Repressor 1 and 2 (SNAI1 and SNAI2), Zinc Finger E-Box Binding Homeobox 1 and 2 (ZEB1 and ZEB2), and the down-regulation, among others, of members of the miR-200 family involved in the maintenance of an epithelial phenotype. Subsequent differentiation to different types of mesenchymal tissues increases tumor heterogeneity and probably modulates clinical behavior and therapy response.

The recent development of new high-throughput technologies for SNP genotyping has opened the possibility of taking a genome-wide linkage approach to the search for new candidate genes involved in heredity diseases. The two major breast cancer susceptibility genes BRCA1 and BRCA2 are involved in 30% of hereditary breast cancer cases, but the discovery of additional breast cancer predisposition genes for the non-BRCA1/2 breast cancer families has so far been unsuccessful.

Next-generation sequencing (NGS) has greatly improved our ability to detect the genomic aberrations occurring in multiple myeloma (MM); however, its transfer to routine clinical labs and its validation in clinical trials remains to be established. We designed a capture-based NGS targeted panel to identify, in a single assay, known genetic alterations for the prognostic stratification of MM. The NGS panel was designed for the simultaneous study of single nucleotide and copy number variations, insertions and deletions, chromosomal translocations and V(D)J rearrangements. The panel was validated using a cohort of 149 MM patients enrolled in the GEM2012MENOS65 clinical trial. The results showed great global accuracy, with positive and negative predictive values close to 90% when compared with available data from fluorescence in situ hybridization and whole-exome sequencing. While the treatments used in the clinical trial showed high efficacy, patients defined as high-risk by the panel had shorter progression-free survival (p = 0.0015). As expected, the mutational status of TP53 was significant in predicting patient outcomes (p = 0.021). The NGS panel also efficiently detected clonal IGH rearrangements in 81% of patients. In conclusion, molecular karyotyping using a targeted NGS panel can identify relevant prognostic chromosomal abnormalities and translocations for the clinical management of MM patients.

The relationship between the ductal and lobular components of invasive ductolobular carcinomas (IDLC) has not been fully elucidated. In this study, the molecular alterations of both components were analyzed in a series of 20 IDLC that were selected, not only by morphologic criteria, but also by the loss of E-cadherin expression in the lobular component. We found that 80% of tumors shared alterations of driver genes in both components, being PIK3CA the most common alteration. In addition, 45% of IDLC carried CDH1 mutations in their lobular component that were absent in the ductal component. Fluorescent in situ hybridization analysis of the CDH1 gene excluded homozygous CDH1 loss as a frequent cause of E-cadherin loss in tumors without CDH1 mutations. In addition, no pathogenic mutations of catenin genes were detected in this series of tumors. In 25% of tumors, actionable mutations in PIK3CA, AKT1, and ERBB2 were found in only 1 component. Altogether, our results confirm that most IDLC derive from invasive carcinoma of no special type, in which a population of cells lose E-cadherin and acquire a lobular phenotype. The frequency of CDH1 mutations in IDLC appears to be lower than in conventional invasive lobular carcinomas, suggesting the implication of alternative mechanisms of E-cadherin loss. Moreover, molecular heterogeneity between ductal and lobular areas suggests the need for molecular characterization of both components to guide targeted therapies.

Background: Immunohistochemistry (IHQ) is commonly used for the detection of mismatch repair proteins deficiency (MMRD). One very infrequent abnormal pattern of MMR protein expression is the loss of PMS2 and MSH6, with intact expression of MLH1 and MSH2. Case presentation: We review the frequency of this MMRD IHC pattern among 108 colorectal (CRCs) and 35 endometrial cancers in our files with loss of expression of at least one protein, and present two CRCs showing loss of PMS2 and MSH6 protein expression (1.9% of CRCs). NGS analysis of these tumours identified PMS2 mutations (R134* germline mutation in one tumour and M1R and c.1239delA somatic mutation in the other) as the primary event and somatic MSH6 mutation (c.3261dupC) as the secondary event in both tumours. Conclusions: This study suggests that Next Generation Sequencing (NGS) tumour analysis should be considered in the algorithm of Lynch syndrome screening to detect MMR gen somatic mutation in inconclusive cases.

Ion homeostasis is critical for numerous cellular processes, and disturbances in ionic balance underlie diverse pathological conditions, including cancer progression. Targeting ion homeostasis is even considered as a strategy to treat cancer. However, very little is known about how ion homeostasis may influence anticancer drug response. In a genome-wide CRISPR-Cas9 resistance drug screen, we identified and validated the master osmostress regulator WNK1 kinase as a modulator of the response to the mitotic inhibitor rigosertib. Osmotic stress and WNK1 inactivation lead to an altered response not only to rigosertib treatment but also to other microtubule-related drugs, minimizing the prototypical mitotic arrest produced by these compounds. This effect is due to an alteration in microtubule stability and polymerization dynamics, likely maintained by fluctuations in intracellular molecular crowding upon WNK1 inactivation. This promotes resistance to microtubule depolymerizing compounds, and increased sensitivity to microtubule stabilizing drugs. In summary, our data proposes WNK1 osmoregulation activity as an important modulator for microtubule-associated chemotherapy response.