Dr. Lok is a Clinician-Scientist at the Princess Margaret Cancer Centre and an Assistant Professor of Radiation Oncology at the University of Toronto. He received his MD from New York University School of Medicine in 2012, during which time he obtained laboratory training followed by postdoctoral research and clinical training at Memorial Sloan Kettering Cancer Center. Since joining Princess Margaret in 2017, Dr. Lok has served as Staff Radiation Oncologist within the Lung Site Group.
The mission of Dr. Lok's laboratory is to improve the outcomes of lung cancer patients by understanding the mechanisms of therapeutic resistance and identifying novel therapeutic targets, particularly those related to DNA repair.
Understanding the predictive biomarker SLFN11 in small cell lung cancer (SCLC)
SCLC is a deadly disease that is initially sensitive to various DNA damaging therapies. Current therapy relies on two broadly used chemotherapeutic agents, cisplatin and etoposide. Identifying predictive biomarkers of response will allow for improved risk stratification and direct personalized therapy for these patients.
One biomarker that predicts for drug response to various DNA damaging therapies - including cisplatin, etoposide and PARP inhibitors - in SCLC is expression of a gene, SLFN11. However, little is known about how SLFN11 mediates therapeutic sensitivity. My laboratory is interested in understanding the mechanism of how SLFN11 sensitizes SCLC to these widely used therapies. By deepening our understanding of this novel biomarker, we will be able to develop future therapies that exploit these discoveries.
Epigenetic targeted therapies for SCLC
Recurrent targetable oncogenic driver mutations are rare in SCLC, instead a hallmark of this disease is loss of two well-known tumor suppressors, TP53 and RB1. Though pharmacologically targeting these pathways is currently difficult, a recent advance in understanding epigenetics and how it applies to SCLC has provided us a way forward in applying targeted therapeutics. We have shown that the dependency of SCLC on EZH2 activity (a methyltransferase that functions on H3K27 and adds a tri-methyl suppressive chromatin mark) leads to chemotherapeutic resistance that can be reversed with inhibitors against EZH2. Remarkably, impressive synergy of EZH2 inhibition with chemotherapy has led to durable responses in preclinical models. Further discovery of epigenetic pathways that are targetable and improve outcomes in SCLC could dramatically change the current treatment paradigm. We propose to leverage the expertise and resources available at the Structural Genomics Consortium to screen a library of epigenetic chemical probes to identify novel therapeutic approaches for SCLC.
Improving translational drug development with circulating-tumor-cell patient-derived xenograft (CDX) models
PDX models have been shown to more closely reflect the biology of their tumors of origin than cell line xenografts. Novel therapeutic testing in PDXs can also more accurately reflect the subsequent experience in human patients. However, PDX generation typically involves surgically resected specimens or core biopsies of sufficient tissue quality – both approaches can be difficult and unnecessary in SCLC patients.
A recent advance to overcome these barriers is the derivation of PDX models from circulating-tumor-cells (CTC) obtained from peripheral blood – known as CDX model. This innovation broadens the patient population who may be able to benefit from personalized xenograft models and allow for larger numbers of diverse tumor models for cancer research. We propose to establish and develop this expertise at our institute to increase availabity of translationally relevant xenograft models to improve drug development and success in future clinical trials.
Proc Natl Acad Sci U S A. 2019 Nov 05;116(45):22429-22431
Cancer. 2019 Oct 08;:
Positron-Emission Tomographic Imaging of a Fluorine 18-Radiolabeled Poly(ADP-Ribose) Polymerase 1 Inhibitor Monitors the Therapeutic Efficacy of Talazoparib in SCLC Patient-Derived Xenografts.
J Thorac Oncol. 2019 Jun 11;:
Langerhans cell histiocytosis in adults is associated with a high prevalence of hematologic and solid malignancies.
Cancer Med. 2019 Jan;8(1):58-66
Int J Part Ther. 2018;4(4):10-19
Clin Cancer Res. 2018 Jun 26;:
Long-term outcomes in oral cavity squamous cell carcinoma with adjuvant and salvage radiotherapy after surgery.
Laryngoscope. 2018 Apr 10;:
Outcome After Radiation Therapy for Langerhans Cell Histiocytosis Is Dependent on Site of Involvement.
Int J Radiat Oncol Biol Phys. 2018 Mar 01;100(3):670-678
Nat Commun. 2018 01 12;9(1):176
Factors influencing the utilization of prophylactic cranial irradiation in patients with limited-stage small cell lung cancer.
Adv Radiat Oncol. 2017 Oct-Dec;2(4):548-554
Clinician Scientist, Princess Margaret Cancer Centre
Assistant Professor, Department of Radiation Oncology, University of Toronto
Assistant Professor, Medical Biophysics, University of Toronto
Assistant Professor, Institute of Medical Science, University of Toronto