Homologous Recombination Deficiency Across Subtypes of Primary Breast Cancer.

Purpose: Homologous recombination deficiency (HRD) is highly prevalent in triple-negative breast cancer (TNBC) and associated with response to PARP inhibition (PARPi). Here, we studied the prevalence of HRD in non-TNBC to assess the potential for PARPi in a wider group of patients with breast cancer.

Methods: HRD status was established using targeted gene panel sequencing (360 genes) and methylation analysis of pretreatment biopsies from 201 patients with primary breast cancer in the phase II PETREMAC trial (ClinicalTrials.

Clonal evolution in primary breast cancers under sequential epirubicin and docetaxel monotherapy.

Background: Subclonal evolution during primary breast cancer treatment is largely unexplored. We aimed to assess the dynamic changes in subclonal composition of treatment-naïve breast cancers during neoadjuvant chemotherapy.

Methods: We performed whole exome sequencing of tumor biopsies collected before, at therapy switch, and after treatment with sequential epirubicin and docetaxel monotherapy in 51 out of 109 patients with primary breast cancer, who were included in a prospectively registered, neoadjuvant single-arm phase II trial.

Assessment of tumor suppressor promoter methylation in healthy individuals.

Background: The number of tumor suppressor genes for which germline mutations have been linked to cancer risk is steadily increasing. However, while recent reports have linked constitutional normal tissue promoter methylation of BRCA1 and MLH1 to ovarian and colon cancer risk, the role of epigenetic alterations as cancer risk factors remains largely unknown, presenting an important area for future research. Currently, we lack fast and sensitive methods for assessment of promoter methylation status across known tumor suppressor genes.

The Functional Roles of the MDM2 Splice Variants P2-MDM2-10 and MDM2-∆5 in Breast Cancer Cells.

Background: MDM2 is a negative regulator of p53 and is upregulated in numerous human cancers. While different MDM2 splice variants have been observed in both normal tissues and malignant cells, their functions are poorly understood.

Methods: We evaluated the effect of MDM2 splice variants by overexpression in MCF-7 cells and analyses of expression of downstream genes (qPCR and Western blot), subcellular localization (immunofluorescence), cell cycle assays (Nucleocounter3000), apoptosis analysis (Annexin V detection), and induction of senescence (β-galactosidase analysis).

Impact of the MDM2 splice-variants MDM2-A, MDM2-B and MDM2-C on cytotoxic stress response in breast cancer cells.

Background: The murine double minute 2 (MDM2) is an oncogene and a negative regulator of the tumor suppressor protein p53. MDM2 is known to be amplified in numerous human cancers, and upregulation of MDM2 is considered to be an alternative mechanism of p53 inactivation. The presence of many splice variants of MDM2 has been observed in both normal tissues and malignant cells; however their impact and functional properties in response to chemotherapy treatment are not fully understood.