Abstract P4-05-07: Functional genomics of TP53 mutations and its impact in breast cancer progression

Somatic TP53 mutations are prevalent in basal-like breast cancer (BLBC) tumors. Patients with BLBC tumors have fewer treatment options and respond poorly to current therapies. The majority of TP53 point mutations occurs in the DNA binding domain and can be categorized as either DNA contact or structural mutations. TP53 mutation results in a dominant negative phenotype with neomorphic activity. We predicted that different p53 mutations may lead to different phenotypic characteristics. To investigate this, we generated MCF10A stable transduced cell lines over-expressing the ten most frequent TP53 point mutations associated with breast cancer located in the DNA binding domain of TP53. Ectopic expression of TP53 in these stable cells has been confirmed by qRT-PCR and immunoblot. To assess the impact of mutation on carcinogenesis, we developed a series of high-throughput quantitative assays that measure several hallmarks of cancer, including proliferation, escape from apoptosis, epithelial to mesenchymal transition (EMT), cell migration and invasion, anoikis and morphology in 3D. We observed that one DNA contact mutation with the substitution of a positively charged amino acid with hydrophobic side chains such as R248W, and two structural mutants Y234C and H179R are resistant to apoptosis in presence of doxorubicin, are the most invasive displaying a mesenchymal phenotype characterized by the presence of disrupted B-catenin and E-cadherin staining, with reported worst clinical outcome, suggesting that these are the most aggressive phenotypes. Interestingly, the DNA contact mutants (R248Q, R273H, R248W, and R273C) had a growth advantage in absence of growth factors while structural mutants (R175H, H179R, Y220C, Y234C and Y163C) were more resistant to apoptosis after the cells were challenged with doxorubicin. G245S is comparable to the MCF10Ap53wt and is less proliferative, sensitive to apoptosis, and neither migratory nor invasive. In comparison, R248W which is one of the most aggressive mutants, together with R273C, and H179R resist anoikis; but Y234C, requires matrix for attachment in order to be invasive. In conjunction, these results confirmed our hypothesis that different TP53 point mutants have distinct phenotypes and functional effects on hallmarks of cancer due to distinct underlying cellular programs. Citation Format: Anasuya Pal, Laura Gonzalez-Malerva, Seron Eaton, Mayra Guzman, Donald Chow, Hongwei Yin, Jin Park, Karen Anderson, Joshua LaBaer. Functional genomics of TP53 mutations and its impact in breast cancer progression [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-05-07.