LMP student seminars: 3 February
Each week during term time, MSc and PhD candidates in the Department of Laboratory Medicine and Pathobiology present their research.
Anyone is welcome. No need to register.
Location: Medical Sciences Building, rooms 4171 or 4279, see below.
As part of the core research curriculum, students taking LMP1001/2/3: Graduate Seminars in Laboratory Medicine and Pathobiology will present their projects. Please see abstracts below.
2. Cancer, Development and Aging
Location: MSB 4171
Tera Petchiny
- Title: Acoustically-stimulated microbubbles act as radiosensitizers in treatment of large-scale prostate tumours in vivo
- Supervisor: Dr. Gregory Czarnota & Dr. JoAnne McLaurin
Ming-Heng Wang
- Title: Deducing the Role of TEADs in Acute Myeloid Leukemia
- Supervisor: Dr. Rod Bremner
2. Cancer, Development and Aging
Location: MSB 4279
Nakita Gopal
- Title: Multi-Omic Profiling of Molecular Heterogeneity in Triple-Negative Breast Cancer
- Supervisor: Dr. Susan J Done
Asa Lau
- Title: Discovering CD47-driven signaling pathways in lung cancer metastasis
- Supervisor: Dr. Kelsie Thu
Abstracts
Tera Petchiny: Acoustically-stimulated microbubbles act as radiosensitizers in treatment of large-scale prostate tumours in vivo
Background: Microbubbles (MB) were originally utilized as ultrasound contrast agents in biomedical imaging but have recently shown promise as radiosensitizers in various cancer treatments. Specifically, treatment with ultrasound-stimulated microbubbles (USMB) increases vascular permeability and induces apoptotic pathways, enhancing tumour cell death when combined with radiation therapy (XRT). This study aims to assess the effectiveness of USMB therapy, using focused ultrasound (FUS), on larger-scale tumours in vivo.
Methods: The generation of 30 large-scale subcutaneous human prostate (PC-3) xenograft tumours in rabbits (n=30) was used to assess tissue response after treatment with MB, FUS, XRT (single-dose 8 Gy), and combinations. The FUS treatments were performed using a novel MRI-guided FUS system (ArrayUS Technologies). Histology, immunohistochemistry (IHC), and Power Doppler imaging analysis were used to assess the overall therapeutic efficacy of USMB and XRT on tumour vasculature, microstructure, and overall cell death.
Results: Preliminary results indicate a significant increase in the degree of cell death observed in the combined treatment group (MB+FUS+XRT) compared to no treatment, MB, FUS, XRT, and MB+FUS, respectively. A significant decrease in microvessel density, vascular index, and cell proliferation was observed in MB+FUS+XRT treatments compared to controls and other treatment cohorts.
Conclusions: USMB, using the ArrayUS clinical system, sensitizes the tumour to radiotherapy by enhancing the amount of cell death and vascular disruption observed in the target region, compared to XRT alone. USMB present a viable combination treatment with the potential to selectively enhance the efficacy of radiotherapy without increasing toxicity.
Ming-Heng Wang: Deducing the Role of TEADs in Acute Myeloid Leukemia
Acute myeloid leukemia (AML) is a highly lethal blood cancer. Despite therapeutic advances, relapse due to drug resistance remains a major concern. There remains a need to identify novel therapeutic strategies.
Our lab discovered that expression or silencing of YAP/TAZ transcriptional coactivators divides all cancers into binary YAPon and YAPoff classes, respectively. In YAPon cancers, YAP/TAZ activate cell cycle genes to drive cancer. In YAPoff cancers, forced YAP expression induces adhesion genes that drive cytostasis and tumor suppression. Whether pro- or anti-cancer, YAP cooperates with TEADs, a family of DNA-binding transcription factors, to induce transcription, but TEADs bind distinct cell cycle or adhesion gene targets in YAPon vs. YAPoff cancers, respectively. YAPon cancers include many solid tumors (e.g. carcinomas, sarcomas) whereas YAPoff cancers include many neural, and all neuroendocrine and hematopoietic tumors. While the anti-cancer effects of YAP arose from our work in neural/neuroendocrine YAPoff cancers, the effect of YAP in AML is unknown.
In YAPon cancers, TEADs cooperate with AP1 to bind and induce cell cycle genes. However, our lab found that in neural/neuroendocrine YAPoff cancers, TEAD binds corepressor proteins. Depleting TEADs induces adhesion genes in YAPoff small cell lung cancer (SCLC) and causes cell death. Thus, TEAD is oncogenic in YAPon cancers and YAPoff SCLC, but through gene activation with YAP or repression with corepressors, respectively. We wondered whether TEADs also have a pro-cancer repressive function in AML.
I found that AML cell lines express much less TEAD than SCLC cells. Unlike SCLC, where TEADs are oncogenic, their low expression in AML might reflect tumor suppressor activity. Using proteomics to identify AML TEAD interactors, I found that in cells overexpressing TEAD4, YAP was a prominent interactor. The parental cells lack YAP, thus over-expressing TEAD4 induces YAP in AML. Others in the lab showed that YAP suppresses AML growth in a TEAD-binding-dependent manner. Together, these data suggest that low TEAD levels in AML ensure YAP remains off, preventing tumor suppression. TEAD depletion induces anti-cancer genes in SCLC, but when I depleted endogenous TEAD4 in AML cells the transcriptome remained unchanged, confirming that TEADs are down regulated to an extent that they do not influence gene expression. Overall, I propose that TEADs can induce YAP to inhibit AML, explaining low TEAD levels in this cancer. This contrasts neural/neuroendocrine YAPoff cancers where TEADs are deployed in a pro-cancer activity to repress anti-cancer adhesion genes. It may be feasible to deploy the anti-cancer functions of TEADs and YAP in AML to improve therapeutic outcome in this highly lethal cancer.
Nakita Gopal: Multi-Omic Profiling of Molecular Heterogeneity in Triple-Negative Breast Cancer
Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer, with more deaths occurring within the first 5 years after diagnosis than other subtypes. Due to the lack of specific targetable alterations in TNBCs, chemotherapy remains the main systemic treatment option, with most TNBC patients receiving neoadjuvant chemotherapy (NAC) prior to surgery along with immunotherapies targeting PD-L1 with varied effects. An important prognostic indicator in breast cancers is a pathologic complete response (pCR) to NAC. Unfortunately, only 40% of TNBCs achieve complete pCR, and in those that do not respond to treatment, around 50% develop recurrence. Currently, the standard for estimating whether a patient’s cancer will recur is an index known as the Residual Cancer Burden (RCB), which can only be determined after surgery when NAC has already been administered and considers factors such as lymph node involvement and tumour size, but not genomic profiling. A precise prognostic genomic test employed prior to initiating treatment could be very valuable as a tool to inform the treatment plan. As few studies have integrated DNA, mRNA, and DNA methylation profiles in residual disease, there is a gap to apply this multi-omic approach to characterize residual post-NAC TNBC. We expect to generate a specific panel of differentially expressed candidate genes associated with residual disease that may predict those most resistant to NAC. By employing a genomic analysis of residual TNBC after NAC using an integrated multiplatform approach, our overall goal is to determine what genomic, epigenomic, and transcriptomic changes are associated with residual TNBC after chemotherapy in order to identify genes that have the strongest prognostic value.
Asa Lau: Discovering CD47-driven signaling pathways in lung cancer metastasis
Introduction: CD47 is a "don't eat me" signal that is often overexpressed and associated with poor prognosis in non-small cell lung cancer (NSCLC). Most studies of CD47 have focused on its role in promoting tumor immune evasion although it has been shown to influence cancer metastasis. We aimed to investigate the transcriptomic changes associated with CD47 blockade that governs signaling pathways involved.
Methods: CRISPR/Cas9 was used to knockout (KO) CD47 in two NSCLC models, LLC and H1299. Scratch assays and tail-vein injections were done to assess the effects of CD47 KO on migration and tumor metastasis. Bulk RNA-sequencing was performed on LLC wild-type (WT) and KO cells collected in culture. Differential gene expression and pathway analysis followed.
Results: Scratch assays revealed that CD47 KO impaired migration H1299 cells in vitro. In vivo, CD47 KO significantly prolonged metastasis-free survival of mice injected with LLC and H1299 cells. Pathway analysis suggests that CD47 KO cells exhibit transcriptomic changes associated with downregulation of TNFα signaling via NFkB. Initial western blot validation show a downregulation of pERK signaling in CD47 KO cells as an upstream regulator of NFkB.
Conclusions: Our findings indicate that CD47 promotes migration and metastasis in NSCLC. Our transcriptomic profiling and initial validation suggests that this could be through TNFα-pERK-NfkB signaling. Further experiments will be conducted to validate the signaling pathway associated with CD47 in migration and metastasis. Altogether, this suggests that CD47-targeted therapy may inhibit lung tumors by antagonizing metastatic spread in addition to tumor immune evasion.
Contact
No need to register.
Contact lmp.grad@utoronto.ca with any questions