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e13021Background: We have previously shown that protein phosphatase 2A (PP2A) may mediate acquired lapatinib resistance and inhibition of PP2A with okadaic acid enhances lapatinib response in vitro...

583 Background: In the TCHL trial (NCT01485926) 78 women with HER2-positive breast cancer (BC) underwent neo-adjuvant treatment with either TCH (Docetaxel, Carboplatin, Trastuzumab) or TCHL (TCH + Lapatinib) therapy. Of the 78 patients, 24 consented to an optional on-treatment biopsy 20 days after 1 cycle of therapy. We analysed the impact of tumour infiltrating lymphocytes (TILs) on pathological complete response (pCR) and also determined the impact of TCH/TCHL therapy on immune cell modulation after 20 days of treatment. Methods: We assessed TIL and stromal lymphocytes (SL) counts using immunohistochemical staining with Haemotoxalyin+Eosin, AE1/AE3 and CD45 in formalin fixed paraffin embedded (FFPE) baseline biopsy samples and in fresh frozen (FF) biopsies taken 20-days post cycle 1 (Day-20) of TCH/TCHL. RNA libraries were generated, using the Truseq mRNA library prep kit on the Neoprep platform and sequenced on the NextSeq 500. We measured the transcriptomic profile of 8 pre and on-treatment sample pairs and then used the Microenvironment Cell Populations (MCP)-counter method to measure the abundance of 10 immune cell populations (T cells, CD8 T cells, cytotoxic lymphocytes, NK cells, B lineage, myeloid dendritic cells, neutrophils, endothelial cells and fibroblasts). Results: We found that higher baseline levels of TILs (p = 0.045) but not SL were associated with an increased likelihood of a patient achieving a pCR to TCH/L based therapy. We found in day 20 on-treatment biopsies of women that subsequently went onto have a pCR that levels of SLs but not TILs were significantly higher (p = 0.049) than in those women who did not have a pCR. Finally we found significant increases in the level of monocytes (p = 0.05) and fibroblasts (p = 0.01), but not other immune cell populations, in the day 20 on-treatment biopsies in comparison with the mutated pre-treatment biopsies. Conclusions: In our study baseline TILs but not SLs have a predictive role in the likelihood of a patient achieving a pCR. We also found that TCHL based therapy significantly altered both monocytes and fibroblasts, indicating a possible role for these immune subtypes in response to TCHL therapy.

587Background: ‘TCHL’ an ICORG phase-II neo-adjuvant study in HER2+ve Breast cancer (BC) assessed the impact of TCH (Docetaxel, Carboplatin, Trastuzumab) versus TCHL (Docetaxel, Carboplatin, Trastu...

591Background: TCGA analysis revealed that somatic EGFR, ERBB2, ERBB3 and ERBB4 mutations (ERBB family mutations) occur alone or co-occur with somatic PIK3CA mutations in 19% of HER2-positive breas...

620 Background: Afatinib is a potent irreversible ErbB family tyrosine kinase inhibitor. We have previously shown that afatinib has anti-proliferative activity in a panel of 8 HER2 positive breast ...

633 Background: Lapatinib (L) is approved for the treatment of trastuzumab (T) resistant HER2 positive metastatic breast cancer. Not all HER2 positive tumors respond to L and patients who initially respond frequently relapse, due to the development of resistance to L. Understanding the molecular changes associated with L resistance may lead to the identification of targets to overcome resistance. Methods: SKBR3 cells were treated with either 250 nM L, or 125nM L and 5 µg/ml T twice weekly for 6 months to establish the resistant cell lines SKBR3-L and -TL. We measured by TUNEL assay the effect of L on apoptotic induction in SKBR3, -L and -TL cells. Gene array analysis of the SKBR3, -L and -TL cells identified differences in the expression of apoptosis-related genes, which were validated by immunoblotting. Finally using combinations of obatoclax (O) and L were tested in L resistant cells. Results: In SKBR3 cells, L (500 nM) induces apoptosis (15.8 ± 2.0%) compared to untreated controls (4.6±2.7%), whilst in SKBR3-L and -TL cells L did not induce significant apoptosis compared to controls. Gene array analysis showed that BAX mRNA is down regulated 3.2 fold in SKBR3-L cells compared to the parental cells. In SKBR3-TL cells, MCL-1 mRNA expression is increased 2.1 fold, whilst BAX mRNA is down regulated 2.1 fold compared to the parental cells. Immunoblotting confirmed that BAX protein expression was reduced in the SKBR3-L (1.5 fold, p=0.058) and significantly reduced in SKBR3-TL cells (2.0 fold, p=0.039) compared to SKBR3. MCL-1 protein expression was significantly increased in the SKBR3-L (1.6 fold, p=0.035) and -TL cells (2.3 fold, p=0.031) compared to SKBR3. Combining O (200 nM) and L (500 nM) in both SKBR3 and SKBR3-L cells produced greater growth inhibition than either drug on its own (SKBR3: 86.9±1.0% vs 73.5±3.1% for L (p

8578 Background: Metastatic melanoma remains an almost certainly fatal disease. Current therapies fail to improve survival rates; therefore it is critical to identify alternate therapies for this d...

587 Background: IGF receptor (IGF1R) signalling has been implicated in resistance to trastuzumab in HER2 positive breast cancer in vitro. However, two previous studies on HER2 positive breast tumor...