SUMMARY: Understanding how small molecules perturb gene expression is critical for guiding drug discovery. We present DOSE-L1000-Viz, a Shiny application that facilitates comprehensive exploration of compound-induced transcriptomic responses across doses, time points, and cell types. Powered by a dose-response database, DOSE-L1000-Viz features interactive visualization, target-centric compound ranking based on efficacy and potency, and a signature search module using reference gene sets derived from generalized additive models. We benchmarked signatures derived from generalized additive models against traditional methods and demonstrated the utility of DOSE-L1000-Viz through use cases in transcription factor modulation and drug repurposing. AVAILABILITY AND IMPLEMENTATION: DOSE-L1000-Viz and the backend data are publicly accessible at: https://dosel1000.com. All code is publicly hosted on GitHub (https://github.com/JmWangBio/DOSEL1000Viz) and archived via Zenodo (https://doi.org/10.5281/zenodo.15532392).

MOTIVATION: The clinical translation of mass spectrometry-based proteomics has been challenging due to limited statistical power caused by large technical variability and inter-patient heterogeneity. Bottom-up proteomics provides an indirect measurement of proteins through digested peptides. This raises the question whether peptide measurements can be used directly to better distinguish differentially expressed proteins. RESULTS: We present a novel method called the peptide set test, which detects coordinated changes in the expression of peptides originating from the same protein and compares them to the rest of the peptidome. Applying our method to data from a published spike-in experiment and simulations demonstrates improved sensitivity without compromising precision, compared to aggregation-based approaches. Additionally, applying the peptide set test to compare the tumor proteomes of tamoxifen-sensitive and tamoxifen-resistant breast cancer patients reveals significant alterations in peptide levels of collagen XII, suggesting an association between collagen XII-mediated matrix reassembly and tamoxifen resistance. Our study establishes the peptide set test as a powerful peptide-centric strategy to infer differential expression in proteomics studies. AVAILABILITY AND IMPLEMENTATION: Peptide set test (PepSetTest) is publicly available at https://github.com/JmWangBio/PepSetTest.

MOTIVATION: The LINCS L1000 project has collected gene expression profiles for thousands of compounds across a wide array of concentrations, cell lines, and time points. However, conventional analysis methods often fall short in capturing the rich information encapsulated within the L1000 transcriptional dose-response data. RESULTS: We present DOSE-L1000, a database that unravels the potency and efficacy of compound-gene pairs and the intricate landscape of compound-induced transcriptional changes. Our study uses the fitting of over 140 million generalized additive models and robust linear models, spanning the complete spectrum of compounds and landmark genes within the LINCS L1000 database. This systematic approach provides quantitative insights into differential gene expression and the potency and efficacy of compound-gene pairs across diverse cellular contexts. Through examples, we showcase the application of DOSE-L1000 in tasks such as cell line and compound comparisons, along with clustering analyses and predictions of drug-target interactions. DOSE-L1000 fosters applications in drug discovery, accelerating the transition to omics-driven drug development. AVAILABILITY AND IMPLEMENTATION: DOSE-L1000 is publicly available at https://doi.org/10.5281/zenodo.8286375.