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The development of spatial transcriptomics technology has revealed the spatial heterogeneity characteristics of drug responses in tissues. The differential responses of cells to drug treatment depend not only on the intrinsic characteristics of the cells but are also closely related to the spatial positioning of cells in the tissue microenvironment, neighborhood cell interactions, and the stromal microenvironment. Therefore, deciphering the spatial locations of drug perturbations with spatial positioning characteristics and explaining the key links of drug action mechanisms also provide a theoretical basis for precision targeted therapy from a spatial dimension.

Here we introduce the SDMap database (http://bio-bigdata.hrbmu.edu.cn/SDMap), whose core goal is to resolve the cellular spatial heterogeneity involved in human drug action and drug resistance in the tissue microenvironment. The database integrates the following resources:

· Multi-dimensional spatial transcriptome data: covering 989 sets of spatial transcriptome datasets, including 969 sets of ordinary resolution data and 20 sets of single-cell resolution data (a total of 20 types of healthy tissues and 21 types of diseased tissues)

· Large-scale drug perturbation data: including 5,490,079 combined experimental data of 33,149 drugs under different concentrations, action times, and cell line conditions

· High-precision spatial site information: including drug-spatial site association data of 5,490,079 spatial locations (2,240,955 traditional spots locations + 3,089,124 single-cell level locations)



Identification of drug-cell/cell type associations



SDMap calculates the perturbation effect score (IS) of drug-related specific instances on spatial loci based on the up-regulated and down-regulated signature gene sets related to drugs under certain action conditions (a certain action dose and action time, i.e., a treatment instance related to drugs) and the expression data of spots/cells on spatial sections. Since the data of spatial transcriptome spot resolution is closer to the distribution of single-cell data, SDMap uses the AUCell method (PMID: 28991892) specially developed for single-cell data to evaluate the activity of up-regulated and down-regulated signature gene sets of drug action instances in loci or cells on spatial sections (for single-cell resolution spatial transcriptome data) and establish instance-spatial locations associations. When inferring the perturbation effect of an instance on a spatial locations, the relationship between the up-regulated and down-regulated genes perturbed by the drug-related instance and the gene expression ranking list in the spatial spot/cell is comprehensively considered. The calculation of the perturbation score ISij of drug-related instance i (i.e., under the background of a certain action dose and duration of the drug) on a certain locus j in the spatial section is as follows:

ISij=AUCScoreupij- AUCScoredownij

Here, AUCScoreupij (AUCScoredownij) respectively represents the AUC Score value calculated for the up-regulated (down-regulated) signature gene set perturbed by instance i in spatial locations j. AUCell uses the "Area Under the Curve" (AUC) to calculate whether a critical subset of the input gene set is enriched at the top of the ranking for each cell. The AUC represents the proportion of expressed genes in the signature and their relative expression value compared to the other genes within the spot/cell (PMID: 28991892). Thus, if ISij > 0, it indicates that the highly expressed genes in spatial locations j are more consistent with the genes up-regulated by instance i perturbation (compared to the gene set down-regulated by instance i perturbation). Then, when instance i acts on spatial locations j, its promoting (up-regulating) effect on the naturally highly expressed genes in the spatial locations is stronger than the inhibiting (down-regulating) effect, that is, ISij > 0 reflects that the instance has a promoting effect on the original state of spatial locations j. Conversely, if ISij < 0, it indicates that the highly expressed genes in spatial locations j are more consistent with the genes down-regulated by instance i perturbation (compared to the gene set up-regulated by instance i perturbation). Then, when instance i acts on spatial locations j, its inhibiting (down-regulating) effect on the naturally highly expressed genes in the spatial locations is stronger than the promoting (up-regulating) effect, that is, ISij < 0 reflects that the instance has an inhibiting effect on the original state of spatial locations j. SDMap calculates the perturbation effect scores between drug-related instances and spatial loci, and for each spatial tissue slice, constructs an instance-spatial locations perturbation effect scoring matrix corresponding to the tissue type of the slice. Here, it is ensured that the cell line environment where the drug-related instances in the matrix act is consistent with the tissue type of the spatial slice.

Furthermore, the significance of the perturbation effect of drug-related instances on spatial loci is evaluated. SDMap constructs the null distribution of the perturbation effect score (IS) of drug-related instances on spatial loci (see Supplementary Materials and Methods for details). Then, the significance threshold is determined based on the constructed null distribution of IS scores: after sorting all background scores, the scores corresponding to the top 2.5% (bottom 2.5%) of the sorting results are taken as the thresholds for the significant promotion (significant inhibition) of spatial loci by drug-related instances. Finally, a binary matrix of perturbation effects between drug-related instances and spatial loci is constructed according to the determined thresholds. For values in the instance-spatial locations perturbation effect IS scoring matrix that are greater than (less than) the significant promotion (inhibition) threshold, it is defined that the instance has a significant promotion (inhibition) effect on the corresponding spatial locations, and is assigned a value of 1 (-1); the remaining values in the matrix are assigned a value of 0, indicating that the corresponding instance has no significant perturbation effect on the spatial locations.