Lab Members

John Witte


jwitte ‘at’, 415-502-6882

John is Professor of Epidemiology and Biostatistics, and Urology, Head of the Division of Genetic and Cancer Epidemiology, Associate Director of the Institute for Human Genetics, and co-Leader of the Cancer Genetics Program at UCSF. He obtained a BS in Mathematical Sciences, a MS in Industrial Engineering and Operations Research, and a PhD in Epidemiology (with Sander Greenland at UCLA). Before joining the faculty at UCSF in 2003, he did a post-doc in Biostatistics and spent eight years on the faculty at Case Western Reserve University. In addition to work, he enjoys spending time with his family and friends, outdoors, and in the swimming pool!

Caroline Tai

Doctoral Student

caroline.tai ‘at’

Caroline is a doctoral student in the Epidemiology and Translational Science program at UCSF. She has a BS in Microbiology from UC San Diego, an MPH in Epidemiology from Emory, and has previously worked in the pharmaceutical industry. Caroline joined John's group in August 2014 is interested in developing risk prediction tools for cancer-related outcomes using genomic data. She enjoys hiking, yoga, and partaking in the Bay Area's many culinary adventures.

Chenan Zhang


chenan.zhang ‘at’

Chenan Zhang completed her Ph.D. in Epidemiology at the University of Chicago’s Department of Public Health Sciences in 2016. She has a BS in Biochemistry and Zoology from the University of Florida and an MS in Marine Science from the University of Texas at Austin. Her doctoral research focused on the role of telomere length as a prospective biomarker of cancer risk. As a postdoc in the Witte Lab, her research will involve investigating genetic variants associated with active surveillance failure for prostate cancer. She will also work with Kyle Walsh in the Division of Neuroepidemiology on genetic susceptibility to pediatric glioma. In her free time, Chenan enjoys tending to her heirloom tomato plants, mushroom hunting, and working out at the gym.

Clinton Cario

Doctoral Student

clint.cario ‘at’

Clint is a PhD student in the BMI program at UCSF. He received bachelor’s degrees in Computer Science and Biochemistry Molecular Biology in 2006 from Penn State, and a Masters in 2010 from Johns Hopkins in Bioinformatics. His current research interests are in tumor heterogeneity and evolution, and using cfDNA (i.e. 'liquid biopsy') to understand tumor genetics. For fun, he likes to hike, play squash, try different ramen restaurants, and cajole people into joining his band.

Emmalyn Chen

Doctoral Student

Emmalyn.Chen ‘at’

Emmalyn is a PhD student in the Pharmaceutical Sciences and Pharmacogenomics (PSPG) program at UCSF. In 2014, she obtained a BS in Bioengineering from UC Berkeley. She is generally interested in using genomic data to better understand disease risk and progression. Specifically, she wants to investigate genetic variants that are driving a multiple cancer phenotype. Outside of the office, you will find her watching nature documentaries, top-rope/bouldering, eating seafood, and hanging out with her cats.

Joel Mefford

Doctoral Student

meffordj ‘at’

Joel is a PhD student in the PSPG program at UCSF. Before coming to UCSF, Joel worked in biotech and participated in microbial ecology and metagenomics research at the University of Southern California and Stanford. His current work with John and other collaborators at UCSF on development and application of statistical tools for genetic epidemiology draws on his training, which includes an MS in statistics from UC Santa Cruz and an MPH from UC Berkeley. He is particularly interested in novel methods for survival and longitudinal analyses in pharmacogenetic studies. Outside of the office, you can find Joel riding his bicycles.

Lancelote Leong

Lab Manager

lancelote.leong ‘at’

Lance has provided post-award grant support to John’s lab since 2011. He joined full-time in 2015 to participate more in its research and the training of its scholars as well as help manage its many projects. He has an AB in History from the University of Chicago, studied French at its Center in Paris, and is currently receiving the greatest education yet learning from the remarkable members of the Witte Lab. He also enjoys drawing, swimming, and spicy food when he can.

Linda Kachuri


linda.kachuri ‘at’

Linda Kachuri joined the Witte lab in February 2018, shortly after completing her PhD in Epidemiology at the University of Toronto under the supervision of Dr. Rayjean Hung. She received an MPH in Epidemiology, also from the University of Toronto in 2012, and a BSc in Psychology from McGill University in 2010. Linda's doctoral research explored the role of rare variants in chromosome 5p15 and telomere length in lung cancer risk and progression. In addition to genetic epidemiology, she is also interested in environmental and occupational cancer risk factors. As a postdoc, Linda is looking forward to working on collaborative projects in prostate cancer, and leveraging genetic and molecular data to gain insight into the mechanisms of cancer etiology and progression. Outside of work Linda enjoys travelling, photography, and exploring the local food scene.

Nima Emami

Doctoral Student

nima.emami ‘at’

Nima is a doctoral student in Biological and Medical Informatics (BMI) at UCSF. In 2013 he received his BS from UC Berkeley, where he studied Bioengineering, Electrical Engineering and Computer Science (EECS). Nima is currently researching the impact of rare genetic variants on prostate cancer risk and progression, and is generally interested in genomics and health. In his free time he enjoys exploring the city, playing tennis and golf, and following Bay Area sports. In fact, some have referred to him as 'Mr. Bay Area' [citation needed].

Rebecca Graff


rebecca.graff ‘at’

Rebecca joined John's lab as postdoctoral scholar in July 2014. She received her BA in Statistics from the University of California, Berkeley in 2006 and completed her ScD in Epidemiology at the Harvard School of Public Health in May 2014. Her doctoral research focused on the TMPRSS2:ERG fusion in prostate cancer, but she has been involved with epidemiological research across several cancer sites. Moving forward, she will focus on genome-wide association studies and genetic risk scores for disease progression. Outside of work, Rebecca plays soccer several times per week, swims, reads, and catches plenty of A's games.

Sara Rashkin


sara.rashkin ‘at’

Sara completed her PhD in Biostatistics at the University of Michigan in December 2015 and joined the lab in January 2016. She received her BA in Statistics from Northwestern University in 2009. Under the mentorship of Dr. Gonçalo Abecasis, her graduate research focused on methods for sequence based studies of complex traits. She worked to determine optimal sequencing strategies for studying very rare variants. She also developed a method for determining copy number variation in a region for a sample of individuals using sequence data. Outside of work, Sara enjoys reading and cooking.

Travis Meyers


travis.meyers ‘at’

Travis completed his MPH and PhD in epidemiology at the UCLA Fielding School of Public Health and joined the Witte Lab in 2017. He earned a BA in biology from Whitman College in Walla Walla, Washington. Dr. Zuo-Feng Zhang supervised Travis’s doctoral research on cumulative cigarette tar exposure, genetic variants, and their interactions on susceptibility and survival of lung and upper aerodigestive tract cancers. Travis is interested in genome-wide association studies as well as gene-environment interaction for cancer risk and progression. A Sacramento native, he enjoys running, tennis, hiking, and spending time with friends and family.



Former Lab Members (& Current Employer)