To understand the mechanisms leading to trastuzumab resistance in HER2-overexpressing breast tumors we created trastuzumab insensitive cell lines (SKBR3/100-8 and BT474/100-2). The cell lines maintain HER2 receptor overexpression, and show increase in EGFR. Upon trastuzumab treatment, SKBR3/100-8 and BT474/100-2 cell lines displayed increased growth rate and invasiveness. The trastuzumab resistance in SKBR3/100-8 and BT474/100-2 was accompanied with activation of the Wnt/β-catenin signaling pathway. Further investigation found that Wnt3 overexpression played a key role toward the development of trastuzumab resistance. The expression of Wnt3 in trastuzumab resistant cells increased nuclear expression of β-catenin and transactivated expression of EGFR. The increased Wnt3 in the trastuzumab resistant cells also promoted a parental EMT-like transition (epithelial to mesenchymal transition), increased N-cadherin, Twist, SLUG and decreased E-cadherin. Knockdown of Wnt3 by siRNA restored cytoplasmic expression of β-catenin, and decreased EGFR expression in trastuzumab resistant cells. Furthermore the EMT markers were decreased, E-cadherin was increased and the cell invasiveness was inhibited in response to the Wnt3 down-regulation. Conversely, SKBR3 cells which had been stably transfected with full-length Wnt3 exhibited EMT-like transition. The Wnt3 transfectants, SKBR3/Wnt3-7 and SKBR3/Wnt3-9, showed a significant decrease in E-cadherin and increase in N-cadherin, Twist and SLUG. The cells were less sensitive to trastuzumab compared to parental SKBR3 and vector transfected cells. In summary, our data suggests that Wnt3 overexpression activates Wnt/β-catenin signaling pathway that leads to transactivation of EGFR and promotes EMT-like transition. This could be an important mechanism leading to trastuzumab resistance in HER2 overexpressing breast cancer cells.

Well-differentiated/de-differentiated liposarcomas (WDLS/DDLS) encompass an intriguing disease model in which a temporal intersection occurs between the malignant transformation of mesenchymal cells and the process of adipogenesis. Deciphering the molecular events that trigger and are characteristic of the intersection of these oncogenic and normal processes is critical to affect the often morbid and lethal consequences of malignant tumors of fat. High-resolution genome-wide oligonucleotide array-based comparative genomic hybridization (aCGH) with matched gene expression analyses was performed on seven lipomas, one hibernoma, and 38 WD and DDLS to define and compare the genomic events associated with these tumors. WD and DDLS had complex karyotypes. On average, WDLS had 11.1 and DDLS had 22.7 chromosomal copy number aberrations. All of the liposarcomas had 12q13-q15 amplifications with varying peaks at CDK4 (12q14.1), HMGA2 (12q14.3), and MDM2 (12q15); 24% of the DDLS and no WDLS had 1p32.2 (JUN) amplifications; 33% WDLS and 35% DDLS had 1q24.3 amplifications involving DNM3 and miR-214/miR-199a2; 24% of the liposarcomas had 6q23-q24 amplifications (including MAP3K5). Amplifications in GLI1 (12q13.3), JUN, and MAP3K5 (6q23.3) were mutually exclusive and occurred predominately in the DDLS. 6q amplifications occurred primarily in retroperitoneal tumors and females represented the majority of those patients who developed fatty tumors prior to the age of 50 years old. This detailed genetic mapping provides insight into the heterogeneity of WD and DDLS and the chromosomal and genetic abnormalities that are present in and distinguish these mesenchymal malignancies.

PLX4032 has robust activity in BRAF mutated melanoma. The preclinical use of this molecule identifies criteria for its proper clinical application, describes patterns of and reasons for response/resistance, and affords insight into the role of a BRAF mutation in melanoma.

ERCC5 is a novel biomarker of ovarian cancer prognosis and a potential therapeutic target of ovarian cancer response to platinum chemotherapy.