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Purpose: Cancer immunotherapy has markedly improved the prognosis of patients with a broad variety of malignancies. However, benefits are weighed against unique toxicities, with immune-related adverse events (irAE) that are frequent and potentially life-threatening. The diagnosis and management of these events are challenging due to heterogeneity of timing onset, multiplicity of affected organs, and lack of non-invasive monitoring techniques. We demonstrate the use of a granzyme B–targeted PET imaging agent (GZP) for irAE identification in a murine model. Experimental Design: We generated a model of immunotherapy-induced adverse events in Foxp3–DTR–GFP mice bearing MC38 tumors. GZP PET imaging was performed to evaluate organs non-invasively. We validated imaging with ex vivo analysis, correlating the establishment of these events with the presence of immune infiltrates and granzyme B upregulation in tissue. To demonstrate the clinical relevance of our findings, the presence of granzyme B was identified through immunofluorescence staining in tissue samples of patients with confirmed checkpoint inhibitor–associated adverse events. Results: GZP PET imaging revealed differential uptake in organs affected by irAEs, such as colon, spleen, and kidney, which significantly diminished after administration of the immunosuppressor dexamethasone. The presence of granzyme B and immune infiltrates were confirmed histologically and correlated with significantly higher uptake in PET imaging. The presence of granzyme B was also confirmed in samples from patients that presented with clinical irAEs. Conclusions: We demonstrate an interconnection between the establishment of irAEs and granzyme B presence and, for the first time, the visualization of those events through PET imaging.

PURPOSE: Standard therapy for HER2+ breast cancers includes HER2 inhibition. While HER2 inhibitors have significantly improved therapeutic outcomes, many patients remain resistant to therapy. An important intrinsic resistance mechanism to HER2 inhibition in some breast cancers is dynamic upregulation of HER3. Increase in HER3 expression that occurs in response to HER2 inhibition allows for continued growth signaling through HER2/HER3 heterodimers, promoting tumor escape. We hypothesized that a non-invasive method to image changes in HER3 expression would be valuable to identify those breast cancers that dynamically upregulate HER3 in response to HER2 inhibition. We further hypothesized that this imaging method could identify those tumors that would benefit by additional HER3 knockdown. PROCEDURES: In a panel of HER2+ breast cancer cell lines treated with the HER2 inhibitor lapatinib, we evaluate changes in HER3 expression and viability. Mouse HER2+ breast cancer models treated with lapatinib were imaged with a peptide-based HER3-specific PET imaging agent [(68)Ga]HER3P1 to assess for dynamic changes in tumoral HER3 expression and uptake confirmed by biodistribution. Subsequently, HER2+ cell lines were treated with the HER2 inhibitor lapatinib as well HER3-specific siRNA to assess for changes in viability and correlate with HER3 expression upregulation. For all statistical comparisons, P

Triple Negative Breast Cancer (TNBC) is an aggressive form of Breast Cancer (BC). Numerous kinase inhibitors (KI) targeting different pathway nodes have shown limited benefit in the clinical setting. In this study, we aim to characterize the extent of HER3 reliance and to define the effect of Neuregulin (NRG) isoforms in TNBCs. Basal and Claudin type TNBC cell lines were treated with a range of small molecule inhibitors, in the presence or absence of the HER3 ligand NRG. Single agent and combination therapy was also evaluated in human cancer cell lines through viability and biochemical assessment of the AKT/MAPK signaling pathway. We show that Basal (BT20, HCC-70, and MDA-MB-468) and Claudin type (MDA-MB-231, BT-549) TNBC cell lines displayed differential reliance on the HER family of receptors. Expression and dynamic HER3 upregulation was predominant in the Basal TNBC subtype. Furthermore, the presence of the natural ligand NRG showed potent signaling through the HER3-AKT pathway, significantly diminishing the efficacy of the AKT and PI3K inhibitors tested. We report that NRG augments the HER3 feedback mechanism for continued cell survival in TNBC. We demonstrate that combination strategies to effectively block the EGFR-HER3-AKT pathway are necessary to overcome compensatory mechanisms to NRG dependent and independent resistance mechanisms. Our findings suggests that the EGFR-HER3 heterodimer forms a major signaling hub and is a key player in tumorigenesis in Basal but not Claudin type TNBC tested. Thus, HER3 could potentially serve as a biomarker for identifying patients in which targeted therapy against the EGFR-HER3-AKT axis would be most valuable.

Background Since the serendipitous discovery of bovine α-lactalbumin made lethal to tumour cells (BAMLET)/human α-lactalbumin made lethal to tumour cells there has been an increased interest in the ability of the two components, oleic acid and α-lactalbumin, to form anti-cancer complexes. Here we have investigated the in-vitro efficacy of the BAMLET complex in killing oral cancer (OC) cells, determined the active component of the complex and investigated possible biological mechanisms. Materials and methods Two OC cell lines (±p53 mutation) and one dysplastic cell line were used as a model of progressive oral carcinogenesis. We performed cell viability assays with increasing BAMLET concentrations to determine the cytotoxic potential of the complex. We further analysed the individual components to determine their respective cytotoxicities. siRNA knockdown of p53 was used to determine its functional role in mediating sensitivity to BAMLET. Cell death mechanisms were investigated by flow cytometry, confocal microscopy and the lactate dehydrogenase assay. Results Our results show that BAMLET is cytotoxic to the OC and dysplastic cell lines in a time and dose-dependent manner. The cytotoxic component was found to be oleic acid, which, can induce cytotoxicity even when not in complex. Our results indicate that the mechanism of cytotoxicity occurs through multiple simultaneous events including cell cycle arrest, autophagy like processes with a minor involvement of necrosis. Conclusion Deciphering the mechanism of cytotoxicity will aid treatment modalities for OC. This study highlights the potential of BAMLET as a novel therapeutic strategy in oral dysplastic and cancerous cells.

Oral Cancer (OC) is a subset of head and neck cancer (HNC) with an annual worldwide incidence of 275,000 cases. OC remains a significant burden worldwide in terms of diagnosis, treatment and prognosis. Despite desirable outcomes in early diagnosed OCs and treatment advances most OCs are detected in advanced stages. The 5-year survival rate of early-stage disease is ∼80% and that of late-stage disease is only ∼20%. Recurrence and chemoresistance from a treatment point of view and pain and disfiguration are important factors contributing to the high morbidity and mortality of OC. Furthermore the process of oral carcinogenesis is complex and not yet fully understood. Consequently numerous potential biomarkers have been hypothesised though controversial results across the board hamper their clinical implementation. Of greatest advantage would be biomarkers signalling early events preceeding OC. Biomarker targets predominately involve deregulated molecular events that participate in cell signalling, growth, survival, motility, angiogenesis and cell cycle control but can also use changes in metabolic genes to discriminate healthy form disease state. Promising potential biomarkers include the growth signalling oncogenes, Epidermal Growth Factor Receptor and Cyclin D1, the anti-growth signalling components p53 and p21, apoptotic effectors such as Bcl-2 and also components involved in immortalisation, angiogenesis, invasion and metastasis processes. Translation of these potential biomakers to the patients is closer than ever though few issues remain to be resolved. Firstly large clinical trials are needed to validate their clinical applicability but also standardised methods of collection, storage and processing methods are needed to minimise variability.

Introduction: Triple Negative Breast Cancer (TNBC) is an aggressive form of Breast Cancer (BC) affecting ~20% of BC patients. TNBC is a highly heterogenous disease and numerous tyrosine kinase inhibitors (TKI) targeting different pathways including the PI3K, AKT and MAPK pathway have shown limited benefit in the clinical setting. Intrinsic and extrinsic resistance mechanisms to TKI are the main reason of therapeutic failure. Signalling from the human epidermal growth factor receptor (HER) family of proteins is dependent on a well-orchestrated series of interactions between family members to form either homo- or heterodimers. The heterodimeric complex formed with HER3 is a particularly potent oncogenic signalling unit that can act as a driver of cancer growth. HER3 upregulation in response to small molecule inhibitors has been shown to rescue a large number of cancers including TNBC. In this study we aim to characterize the extent of HER3 reliance in TNBC and to define the effect of neuregulin isoforms in TNBC cancers. Method and Materials: Basal and Claudin type Breast cancer cell lines were treated with a range of small molecule inhibitors, known to exhibit limited efficacy as single agents, including the AKT inhibitor (GDC0068), the PI3K inhibitor (GDC0077) and the EGFR inhibitors (Gefitinib and Lapatinib) or a combination of these drugs in the presence or absence of the HER3 ligand neuregulin. The effect these inhibitors on Akt/ MAPK signalling was characterized using specific biomarkers of the respective pathways. Combination therapy was evaluated in human cancer cell lines through Annexin V staining. Results: Basal (HCC-70 and MDA-MB-468) and Caudin type (MDA-MB-231) TNBC cell lines displayed differential reliance on the HER family of receptors. Dynamic HER3 upregulation was predominant in the TNBC cells that show HER signaling reliance coinciding with the basal subtype. Furthermore, the presence of the natural ligand neuregulin showed potent signaling through the HER3-AKT pathway and significantly diminished the efficacy of the inhibitors tested. We report that neuregulin augments the HER3 feedback mechanism for continued proliferation in TNBC. Interestingly, we show that neuregulin mediated resistance is dependent on the type and dose of the neuregulin isoform. Neuregulin 1β showed potent proliferative effects and overcoming this effect required a 10 fold increase in the drug concentration. In contrast, the presence of neuregulin 1α isoform may paradoxically confer sensitivity to small molecule inhibitors. We show that cellular proliferation is maintained through both the PI3K and MAPK pathway and single targeting is inefficient in overcoming resistance. We demonstrate that combination strategies that block compensatory mechanisms are effective strategies to neuregulin dependent and independent resistance mechanisms. Conclusion: The highly dynamic nature of HER3 expression and signalling combined with redundant HER signalling and downstream mechanisms allow for continued signalling in a subtype of TNBC patients. Targeted therapy to ensure complete abrogation of HER signalling is essential for effective therapeutic response. In conclusion, TNBC cancers display differential mechanism of resistance that should be adequately addressed for therapeutic strategies. Citation Format: Nicoleta Sinevici, Pedram Heidari, Umar Mahmood. Her3 up regulation in response to AKT and PI3K inhibition causes differential responses dependent on the presence of neuregulin isoforms in the microenvironmental milieu [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1424.