HER2-enriched subtype and novel molecular subgroups drive aromatase inhibitor resistance and an increased risk of relapse in early ER+/HER2+ breast cancer

BACKGROUND: Oestrogen receptor positive/ human epidermal growth factor receptor positive (ER+/HER2+) breast cancers (BCs) are less responsive to endocrine therapy than ER+/HER2- tumours. Mechanisms underpinning the differential behaviour of ER+HER2+ tumours are poorly characterised. Our aim was to identify biomarkers of response to 2 weeks’ presurgical AI treatment in ER+/HER2+ BCs. METHODS: All available ER+/HER2+ BC baseline tumours (n=342) in the POETIC trial were gene expression profiled using BC360™ (NanoString) covering intrinsic subtypes and 46 key biological signatures. Early response to AI was assessed by changes in Ki67 expression and residual Ki67 at 2 weeks (Ki672wk). Time-To-Recurrence (TTR) was estimated using Kaplan-Meier methods and Cox models adjusted for standard clinicopathological variables. New molecular subgroups (MS) were identified using consensus clustering. FINDINGS: HER2-enriched (HER2-E) subtype BCs (44.7% of the total) showed poorer Ki67 response and higher Ki672wk (p<0.0001) than non-HER2-E BCs. High expression of ERBB2 expression, homologous recombination deficiency (HRD) and TP53 mutational score were associated with poor response and immune-related signatures with High Ki672wk. Five new MS that were associated with differential response to AI were identified. HER2-E had significantly poorer TTR compared to Luminal BCs (HR 2.55, 95% CI 1.14–5.69; p=0.0222). The new MS were independent predictors of TTR, adding significant value beyond intrinsic subtypes. INTERPRETATION: Our results show HER2-E as a standardised biomarker associated with poor response to AI and worse outcome in ER+/HER2+. HRD, TP53 mutational score and immune-tumour tolerance are predictive biomarkers for poor response to AI. Lastly, novel MS identify additional non-HER2-E tumours not responding to AI with an increased risk of relapse

Cellular carriers of viral vectors for turmour selective targeting of cancer gene therapy

Cancer gene therapy holds promise for patients, yet key issues involving the delivery of vector and achieving tumour selective cytotoxicity, has limited progress over recent years. In this thesis a combination of cell-based carriers, viral vectors and tumour selective promoters are assessed to tackle these two important issues directly. Initially two retroviral systems were considered: intracellular carriage of a rapamycin-inducible retrovirus and extracellular carriage ('hitchhiking') of a self-inactivating (SIN) retroviral vector. Both systems controlled transgene expression using the tumour selective human telomerase reverse transcriptase and telomerase RNA promoters (hTERTp & hTRp). Direct transduction of target cells with SIN marker virus, expressing enhanced Green Fluorescent Protein (eGFP) under the internal control of human telomerase reverse transcriptase promoter (hTERTp) demonstrated similar activity to a positive control virus, with some evidence of telomerase selectivity. Hitchhiking of the same SIN marker vectors also mediated eGFP expression in target cells. In contrast the therapeutic SIN vectors containing suicide transgenes did not achieve a reliable direct telomeraseltumour selective cytotoxic effect, with no discernible toxicity seen with hitchhiked vector. The rapamycin-inducible vectors in contrast to the SIN vectors only demonstrated retroviral genome expression following single cell cloning of a positive-control producer cell line. The retrovirus from this producer successfully mediated low-level target cell eGFP expression, however the data did not support development of therapeutic vectors in,corporating either telomerase promoter. Incorporating oncolytic viruses into the system allowed in vitro therapy. An eGFP expressing oncolytic vesicular stomatitis virus (VSV) and wild-type reovirus, showed direct cytotoxicity against a range of target cell lines. T-cell and non-T-cell peripheral blood mononuclear cell (PBMC) fractions were resistant to both viruses indicating their suitability as oncolytic viral carriers. Finally VSV was successfully hitchhiked on donor T-Iymphocytes leading to the release of VSV .and widespread replication within the malignant Molt-4 cell line.EThOS - Electronic Theses Online ServiceGBUnited Kingdo