BioCanRx Summit for Cancer Immunotherapy 2022 Proceedings.

From 19 to 21 November 2022, BioCanRx held its first post-pandemic in-person Summit for Cancer Immunotherapy in Montreal, Canada. The meeting was well attended by patients, trainees, researchers, clinicians, and industry professionals, who came together to discuss the current state and future of biotherapeutics for cancer in Canada and beyond. Three plenaries, three keynote speakers, a lively debate, and panel discussions, together with poster sessions and a social event, made the event memorable and productive. The current state of cellular therapies, cellular engineering, clinical trials, and the role of the cancer microbiome were discussed in plenary session, and the patient voice was welcomed and present throughout the meeting, in large part due to the Learning Institute, a BioCanRx initiative to include patient partners in research. In this meeting review, we highlight the platform presentations, keynote speakers, debate combatants, panellists, and the patient perspective on the annual meeting.

Synthetic virology approaches to improve the safety and efficacy of oncolytic virus therapies.

The large coding potential of vaccinia virus (VV) vectors is a defining feature. However, limited regulatory switches are available to control viral replication as well as timing and dosing of transgene expression in order to facilitate safe and efficacious payload delivery. Herein, we adapt drug-controlled gene switches to enable control of virally encoded transgene expression, including systems controlled by the FDA-approved rapamycin and doxycycline. Using ribosome profiling to characterize viral promoter strength, we rationally design fusions of the operator element of different drug-inducible systems with VV promoters to produce synthetic promoters yielding robust inducible expression with undetectable baseline levels. We also generate chimeric synthetic promoters facilitating additional regulatory layers for VV-encoded synthetic transgene networks. The switches are applied to enable inducible expression of fusogenic proteins, dose-controlled delivery of toxic cytokines, and chemical regulation of VV replication. This toolbox enables the precise modulation of transgene circuitry in VV-vectored oncolytic virus design.

A retrospective analysis of ezrin protein and mRNA expression in breast cancer: Ezrin expression is associated with patient survival and survival of patients with receptor-positive disease.

INTRODUCTION: The cytoskeletal protein ezrin is upregulated in many cancer types and is strongly associated with poor patient outcome. While the clinical and prognostic value of ezrin has been previously evaluated in breast cancer, most studies to date have been conducted in smaller cohorts (less than 500 cases) or have focused on specific disease characteristics. The current study is the largest of its kind to evaluate ezrin both at the protein and mRNA levels in early-stage breast cancer patients using the Nottingham (n = 1094) and METABRIC (n = 1980) cohorts, respectively. RESULTS: High expression of ezrin was significantly associated with larger tumour size (p = 0.027), higher tumour grade (p < 0.001), worse Nottingham Prognostic Index prognostic group (p = 0.011) and HER2-positive status (p = 0.001). High ezrin expression was significantly associated with adverse survival of breast cancer patients (p < 0.001) and remained associated with survival in multivariate Cox-regression analysis (p = 0.018, hazard ratio (HR) = 1.343, 95% confidence interval (CI) = 1.051-1.716) when potentially confounding factors were included. High ezrin expression was significantly associated with adverse survival of patients whose tumours were categorised as receptor (oestrogen receptor (ER), progesterone receptor (PgR) or HER2) positive (p < 0.001) in comparison to those categorised as triple-negative breast cancer (p = 0.889). High expression of ezrin mRNA (VIL2) in the METABRIC cohort was also significantly associated with adverse survival of breast cancer patients (p < 0.001). CONCLUSION: Retrospective analyses show that ezrin is an independent prognostic marker, with higher expression associated with shortened survival in receptor-positive (ER, PgR or HER2) patients. Ezrin expression is associated with more aggressive disease and may have clinical utility as a biomarker of patient prognosis in early-stage breast cancer.

Targeting the Ezrin Adaptor Protein Sensitizes Metastatic Breast Cancer Cells to Chemotherapy and Reduces Neoadjuvant Therapy-induced Metastasis.

The main cause of cancer-associated deaths is the spread of cancer cells to distant organs. Despite its success in the primary tumor setting, modern chemotherapeutic strategies are rendered ineffective at treating metastatic disease, largely due to the development of resistance. The adaptor protein ezrin has been shown to promote cancer metastasis in multiple preclinical models and is associated with poor prognosis in several cancer types, including breast cancer. Ezrin promotes pro-survival signaling, particularly in disseminated cancer cells, to facilitate metastatic outgrowth. However, the role of ezrin in breast cancer chemoresistance is not fully known. In this study, we show that upregulating or downregulating ezrin expression modifies the sensitivity of breast cancer cells to doxorubicin and docetaxel treatment in vitro and is associated with changes in PI3K/Akt and NFκB pathway activation. In addition, we tested the effects of systemic treatment with a small-molecule ezrin inhibitor, NSC668394, on lung metastatic burden in vivo as a monotherapy, or in combination with anthracycline- or taxane-based chemotherapy treatment. We show that anti-ezrin treatment alone reduces metastatic burden and markedly sensitizes metastases to doxorubicin or docetaxel in neoadjuvant as well as neoadjuvant plus adjuvant treatment models. Taken together, our findings demonstrate the impact of anti-ezrin treatment in modulating response to chemotherapy in breast cancer cells as well as the efficacy of anti-ezrin treatment in combination with chemotherapy at reducing metastatic burden. Significance: This work provides preclinical evidence for combining anti-ezrin treatment with chemotherapy as a novel strategy for effectively targeting metastasis, particularly in a neoadjuvant treatment setting.

Modulation of Akt vs Stat3 activity by the focal adhesion kinase in non-neoplastic mouse fibroblasts.

Adhesion of cells to each other and to the extracellular matrix (ECM) are both required for cellular functions. Cell-to-cell adhesion is mediated by cadherins, and their engagement triggers the activation of Stat3, which offers a potent survival signal. Adhesion to the ECM on the other hand, activates FAK which attracts and activates Src, as well as receptor tyrosine kinases (RTKs), the PI3k/Akt and Ras/Erk pathways. However, the effect of cell density upon FAK and Akt activity has not been examined. We now demonstrate that, interestingly, despite being potent Stat3 activators, Src and RTKs are unable to activate Stat3 in sparsely growing (i.e., without cadherin engagement), non-neoplastic cells attached to the ECM. In contrast, cell aggregation (i.e., cadherin engagement in the absence of adhesion to a solid substratum) was found to activate both Stat3 and Akt. Pharmacologic or genetic reduction of FAK activity abolished Akt activity at low densities, indicating that FAK is an important activator of Akt in this setting. Notably, FAK knockout increased cellular sensitivity to the Stat3 inhibitor CPA7, while FAK reintroduction restored resistance to this drug. These findings suggest a complementary role of integrin/FAK/Akt and cadherin/Stat3-mediated pro-survival pathways, which may be of significance during neoplastic transformation and metastasis.

Modulation of Akt vs Stat3 activity by the focal adhesion kinase in non-neoplastic mouse fibroblasts.

Adhesion of cells to each other and to the extracellular matrix (ECM) are both required for cellular functions. Cell-to-cell adhesion is mediated by cadherins and their engagement triggers the activation of Stat3, which offers a potent survival signal. Adhesion to the ECM on the other hand, activates FAK which attracts and activates Src, as well as receptor tyrosine kinases (RTKs), the PI3k/Akt and Ras/Erk pathways. However, the effect of cell density upon FAK and Akt activity has not been examined. We now demonstrate that, interestingly, despite being potent Stat3 activators, Src and RTKs are unable to activate Stat3 in sparsely growing (i.e., without cadherin engagement), non-neoplastic cells attached to the ECM. In contrast, cell aggregation (i.e., cadherin engagement in the absence of adhesion to a solid substratum) was found to activate both Stat3 and Akt. Pharmacologic or genetic reduction of FAK activity abolished Akt activity at low densities, indicating that FAK is an important activator of Akt in this setting. Notably, FAK knockout increased cellular sensitivity to the Stat3 inhibitor CPA7, while FAK reintroduction restored resistance to this drug. These findings suggest a complementary role of integrin/FAK/Akt and cadherin/Stat3-mediated pro-survival pathways, which may be of significance during neoplastic transformation and metastasis.

Differentiation of Mouse Breast Epithelial HC11 and EpH4 Cells.

Cadherins play an important role in the regulation of cell differentiation as well as neoplasia. Here we describe the origins and methods of the induction of differentiation of two mouse breast epithelial cell lines, HC11 and EpH4, and their use to study complementary stages of mammary gland development and neoplastic transformation. The HC11 mouse breast epithelial cell line originated from the mammary gland of a pregnant Balb/c mouse. It differentiates when grown to confluence attached to a plastic Petri dish surface in medium containing fetal calf serum and Hydrocortisone, Insulin and Prolactin (HIP medium). Under these conditions, HC11 cells produce the milk proteins ß-casein and whey acidic protein (WAP), similar to lactating mammary epithelial cells, and form rudimentary mammary gland-like structures termed "domes". The EpH4 cell line was derived from spontaneously immortalized mouse mammary gland epithelial cells isolated from a pregnant Balb/c mouse. Unlike HC11, EpH4 cells can fully differentiate into spheroids (also called mammospheres) when cultured under three-dimensional (3D) growth conditions in HIP medium. Cells are trypsinized, suspended in a 20% matrix consisting of a mixture of extracellular matrix proteins produced by Engelbreth-Holm-Swarm (EHS) mouse sarcoma cells, plated on top of a layer of concentrated matrix coating a plastic Petri dish or multiwell plate, and covered with a layer of 10% matrix-containing HIP medium. Under these conditions, EpH4 cells form hollow spheroids that exhibit apical-basal polarity, a hollow lumen, and produce ß-casein and WAP. Using these techniques, our results demonstrated that the intensity of the cadherin/Rac signal is critical for the differentiation of HC11 cells. While Rac1 is necessary for differentiation and low levels of activated RacV12 increase differentiation, high RacV12 levels block differentiation while inducing neoplasia. In contrast, EpH4 cells represent an earlier stage in mammary epithelial differentiation, which is inhibited by even low levels of RacV12.

An epigenetic increase in mitochondrial fission by MiD49 and MiD51 regulates the cell cycle in cancer: Diagnostic and therapeutic implications.

Excessive proliferation and apoptosis-resistance are hallmarks of cancer. Increased dynamin-related protein 1 (Drp1)-mediated mitochondrial fission is one of the mediators of this phenotype. Mitochondrial fission that accompanies the nuclear division is called mitotic fission and occurs when activated Drp1 binds partner proteins on the outer mitochondrial membrane. We examine the role of Drp1-binding partners, mitochondrial dynamics protein of 49 and 51 kDa (MiD49 and MiD51), as drivers of cell proliferation and apoptosis-resistance in non-small cell lung cancer (NSCLC) and invasive breast carcinoma (IBC). We also evaluate whether inhibiting MiDs can be therapeutically exploited to regress cancer. We show that MiD levels are pathologically elevated in NSCLC and IBC by an epigenetic mechanism (decreased microRNA-34a-3p expression). MiDs silencing causes cell cycle arrest through (a) increased expression of cell cycle inhibitors, p27Kip1 and p21Waf1 , (b) inhibition of Drp1, and (c) inhibition of the Akt-mTOR-p70S6K pathway. Silencing MiDs leads to mitochondrial fusion, cell cycle arrest, increased apoptosis, and tumor regression in a xenotransplant NSCLC model. There are positive correlations between MiD expression and tumor size and grade in breast cancer patients and inverse correlations with survival in NSCLC patients. The microRNA-34a-3p-MiDs axis is important to cancer pathogenesis and constitutes a new therapeutic target.

Regulation of Differentiation of HC11 Mouse Breast Epithelial Cells by the Signal Transducer and Activator of Transcription-3.

BACKGROUND/AIM: The differentiation of the mouse breast epithelial cell line HC11 is known to require confluence as well as the addition of hydrocortisone, insulin and prolactin. MATERIALS AND METHODS: Since confluence, which triggers the engagement of the cell-to-cell adhesion molecule E-cadherin, induces a dramatic increase in the activity of signal transducer and activator of transcription-3 (Stat3), we examined the role of Stat3 in HC11 cell differentiation. RESULTS: Stat3 inhibition abolished differentiation, indicating that Stat3 activity is critically required. However, expression of the mutationally activated form of Stat3 (Stat3C), rather than promoting, it was found to block cell differentiation, even when expressed in low levels, and in the absence of full neoplastic conversion. CONCLUSION: The strength of the E-cadherin/Stat3 signal is key for the outcome of the differentiation process.

Intravital imaging reveals systemic ezrin inhibition impedes cancer cell migration and lymph node metastasis in breast cancer.

BACKGROUND: Limited understanding of the cancer biology of metastatic sites is a major factor contributing to poor outcomes in cancer patients. The regional lymph nodes are the most common site of metastasis in most solid cancers and their involvement is a strong predictor of relapse in breast cancer (BC). We have previously shown that ezrin, a cytoskeletal-membrane linker protein, is associated with lymphovascular invasion and promotes metastatic progression in BC. However, the efficacy of pharmacological inhibition of ezrin in blocking cancer cell migration and metastasis remains unexplored in BC. METHODS: We quantified ezrin expression in a BC tissue microarray (n = 347) to assess its correlation with risk of relapse. Next, we developed a quantitative intravital microscopy (qIVM) approach, using a syngeneic lymphatic reporter mouse tumor model, to investigate the effect of systemic ezrin inhibition on cancer cell migration and metastasis. RESULTS: We show that ezrin is expressed at significantly higher levels in lymph node metastases compared to matched primary tumors, and that a high tumor ezrin level is associated with increased risk of relapse in BC patients with regional disease. Using qIVM, we observe a subset of cancer cells that retain their invasive and migratory phenotype at the tumor-draining lymph node. We further show that systemic inhibition of ezrin, using a small molecule compound (NSC668394), impedes the migration of cancer cells in vivo. Furthermore, systemic ezrin inhibition leads to reductions in metastatic burden at the distal axillary lymph node and lungs. CONCLUSIONS: Our findings demonstrate that the tumor ezrin level act as an independent biomarker in predicting relapse and provide a rationale for therapeutic targeting of ezrin to reduce the metastatic capacity of cancer cells in high-risk BC patients with elevated ezrin expression.

Combined targeting of Raf and Mek synergistically inhibits tumorigenesis in triple negative breast cancer model systems.

Aberrant Ras-MAPK signaling from receptor tyrosine kinases (RTKs), including epidermal growth factor receptor (EGFR) and human epidermal growth factor receptor-2 (HER2), is a hallmark of triple negative breast cancer (TNBC); thus providing rationale for targeting the Ras-MAPK pathway. Components of this EGFR/HER2-Ras-Raf-Mek-Erk pathway were co-targeted in the MDA-MB-231 and MDA-MB-468 human TNBC cell lines, and in vitro effects on signaling and cytotoxicity, as well as in vivo effects on xenograft tumor growth and metastasis were assessed. The dual EGFR/HER2 inhibitor lapatinib (LPN) displayed greater cytotoxic potency and MAPK signaling inhibition than the EGFR inhibitor erlotinib, suggesting both EGFR and HER2 contribute to MAPK signaling in this TNBC model. The Raf inhibitor sorafenib (SFN) or the Mek inhibitor U0126 suppressed MAPK signaling to a greater extent than LPN; which correlated with greater cytotoxic potency of SFN, but not U0126. However, U0126 potentiated the cytotoxic efficacy of LPN and SFN in an additive and synergistic manner, respectively. This in-series Raf-Mek co-targeting synergy was recapitulated in orthotopic mouse xenografts, where SFN and the Mek inhibitor selumitinib (AZD6244) inhibited primary tumor growth and pulmonary metastasis. Raf and Mek co-inhibition exhibits synergy in TNBC models and represent a promising combination therapy for this aggressive breast cancer type.

Regulation of HC11 mouse breast epithelial cell differentiation by the E-cadherin/Rac axis.

It was previously demonstrated that differentiation of some established breast epithelial cell lines requires confluence and stimulation with hydrocortisone, insulin and prolactin inducers. We and others previously demonstrated that E-cadherin engagement, which is favored under conditions of confluence, increases the levels and activity of the Rac small GTPase. To investigate the functional relationship between the transforming ability of Rac and its role as an integral component of the differentiative E-cadherin signaling pathway, we introduced a mutationally activated form of Rac, RacV12, into the mouse breast epithelium-derived cell line, HC11. Our results demonstrate that the strength of the Rac signal is key for the outcome of the differentiation process; cRac1 is critically required for differentiation, and at low levels, mutationally activated RacV12 is able to increase differentiation, presumably reinforcing the E-cadherin/Rac differentiative signal. However, high RacV12 expression blocked differentiation concomitant with E-cadherin downregulation, while inducing neoplastic transformation. Therefore, the intensity of the Rac signal is a central determinant in the balance between cell proliferation vs differentiation, two fundamentally opposed processes, a finding which could also have important therapeutic implications.

Cell-cell and cell-matrix adhesion in survival and metastasis: Stat3 versus Akt.

Both cell-cell and cell-matrix adhesion are important for epithelial cell differentiation and function. Classical cadherins mediate cell to cell interactions and are potent activators of the signal transducer and activator of transcription (Stat3), thereby offering survival signaling. While the epithelial (E)-cadherin is required for cells to remain tightly associated within differentiated epithelial tissues, cadherin-11 promotes invasion and metastasis, preferentially to the bone. Cell adhesion to the extracellular matrix is mediated through the integrin receptors that bind to the focal adhesion kinase (FAK)/Src complex, thus activating downstream effectors such as Ras/Erk1/2 and PI3k/Akt, but not Stat3. Therefore, at high densities of cultured cells or in epithelial tissues, co-ordinate activation of the complementary cadherin/Stat3 and integrin/FAK pathways can greatly enhance survival and growth of tumor cells. In neoplastically transformed cells on the other hand, a variety of oncogenes including activated Src or receptor tyrosine kinases, activate both pathways. Still, most single-agent therapies directed against these signaling pathways have proven disappointing in the clinic. Combined targeting of the Src/FAK and Stat3 pathways with inhibitory drugs would be expected to have greater efficacy in inhibiting tumor cell survival, and enhancing sensitivity to conventional cytotoxic drugs for treatment of metastatic disease.

Ezrin regulates focal adhesion and invadopodia dynamics by altering calpain activity to promote breast cancer cell invasion.

Up-regulation of the cytoskeleton linker protein ezrin frequently occurs in aggressive cancer types and is closely linked with metastatic progression. However, the underlying molecular mechanisms detailing how ezrin is involved in the invasive and metastatic phenotype remain unclear. Here we report a novel function of ezrin in regulating focal adhesion (FA) and invadopodia dynamics, two key processes required for efficient invasion to occur. We show that depletion of ezrin expression in invasive breast cancer cells impairs both FA and invadopodia turnover. We also demonstrate that ezrin-depleted cells display reduced calpain-mediated cleavage of the FA and invadopodia-associated proteins talin, focal adhesion kinase (FAK), and cortactin and reduced calpain-1-specific membrane localization, suggesting a requirement for ezrin in maintaining proper localization and activity of calpain-1. Furthermore, we show that ezrin is required for cell directionality, early lung seeding, and distant organ colonization but not primary tumor growth. Collectively our results unveil a novel mechanism by which ezrin regulates breast cancer cell invasion and metastasis.

A novel role for ezrin in breast cancer angio/lymphangiogenesis.

INTRODUCTION: Recent evidence suggests that tumour lymphangiogenesis promotes lymph node metastasis, a major prognostic factor for survival of breast cancer patients. However, signaling mechanisms involved in tumour-induced lymphangiogenesis remain poorly understood. The expression of ezrin, a membrane cytoskeletal crosslinker and Src substrate, correlates with poor outcome in a diversity of cancers including breast. Furthermore, ezrin is essential in experimental invasion and metastasis models of breast cancer. Ezrin acts cooperatively with Src in the regulation of the Src-induced malignant phenotype and metastasis. However, it remains unclear if ezrin plays a role in Src-induced tumour angio/lymphangiogenesis. METHODS: The effects of ezrin knockdown and mutation on angio/lymphangiogenic potential of human MDA-MB-231 and mouse AC2M2 mammary carcinoma cell lines were examined in the presence of constitutively active or wild-type (WT) Src. In vitro assays using primary human lymphatic endothelial cells (hLEC), an ex vivo aortic ring assay, and in vivo tumour engraftment were utilized to assess angio/lymphangiogenic activity of cancer cells. RESULTS: Ezrin-deficient cells expressing activated Src displayed significant reduction in endothelial cell branching in the aortic ring assay in addition to reduced hLEC migration, tube formation, and permeability compared to the controls. Intravital imaging and microvessel density (MVD) analysis of tumour xenografts revealed significant reductions in tumour-induced angio/lymphangiogenesis in ezrin-deficient cells when compared to the WT or activated Src-expressing cells. Moreover, syngeneic tumours derived from ezrin-deficient or Y477F ezrin-expressing (non-phosphorylatable by Src) AC2M2 cells further confirmed the xenograft results. Immunoblotting analysis provided a link between ezrin expression and a key angio/lymphangiogenesis signaling pathway by revealing that ezrin regulates Stat3 activation, VEGF-A/-C and IL-6 expression in breast cancer cell lines. Furthermore, high expression of ezrin in human breast tumours significantly correlated with elevated Src expression and the presence of lymphovascular invasion. CONCLUSIONS: The results describe a novel function for ezrin in the regulation of tumour-induced angio/lymphangiogenesis promoted by Src in breast cancer. The combination of Src/ezrin might prove to be a beneficial prognostic/predictive biomarker for early-stage metastatic breast cancer.