Biostatistics Dept Seminar: A Robust, Scalable K-statistic for Quantifying Immune Cell Clustering in Spatial Proteomics Data

Biostatistics Department Seminar 

Title: A robust, scalable K-statistic for quantifying immune cell clustering in spatial proteomics data

Abstract: The tumor microenvironment (TME), which characterizes the tumor and its surroundings, plays a critical role in understanding cancer development and progression. Recent advances in tissue imaging, including multiplex imaging and other spatial proteomics techniques, have enabled the study of the TME’s spatial structure at a single-cell level.  Many approaches for analyzing spatial relationships in this data are based on point process theory, and among these Ripley's K statistic and its variants are both extremely popular and highly effective. In this framework, cell locations are modeled as a point process, and these metrics aim to quantify spatial correlations between cells. Under the assumption that the rate of cells is constant over an entire tissue area, a point pattern exhibits complete spatial randomness (CSR), and deviations from CSR, such as cell clustering, are of interest. However, spatial proteomics data often contain gaps due to tissue folds or tears, resulting in regions without cells, which can bias the estimation of Ripley's K by violating the assumption of spatial homogeneity. One correction addresses this by permuting an empirical value of CSR, and then comparing observed spatial summary statistic values to that obtained by this empirical null distribution. While effective in small samples, this approach becomes computationally impractical as the number of cells per image increases. To overcome this limitation, we derived a closed-form representation of the empirical null distribution for Ripley's K, which is both fast and easy to implement using existing software. We evaluate the performance of this statistic in simulations and publicly available spatial proteomics data.

Speakers

Julia Wrobel is an assistant professor in the Department of Biostatistics and Bioinformatics in the Rollins School of Public Health at Emory University.

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2023-2024 Monday Seminar Series

All seminars are held at 12:05 PM via Zoom and onsite. View all seminar information here.