Extracellular matrix alterations in low‐grade lung adenocarcinoma compared with normal lung tissue by imaging mass spectrometry

Abstract

Lung adenocarcinoma (LUAD) is the second most common cancer, affecting both men and women. Fibrosis is a hallmark of LUAD occurring throughout progression with excess production of extracellular matrix (ECM) components that lead to metastatic cell processes. Understanding the ECM cues that drive LUAD progression has been limited due to a lack of tools that can access and report on ECM components within the complex tumor microenvironment. Here, we test whether low-grade LUAD can be distinguished from normal lung tissue using a novel ECM imaging mass spectrometry (ECM IMS) approach. ECM IMS analysis of a tissue microarray with 20 low-grade LUAD tissues and 20 normal lung samples from 10 patients revealed 25 peptides that could discriminate between normal and low-grade LUAD using area under the receiveroperating curve (AUC) ≥0.7, P value ≤.001. Principal component analysis demonstrated that 62.4% of the variance could be explained by sample origin from normal or low-grade tumor tissue. Additional work performed on a wedge resection with moderately differentiated LUAD demonstrated that the ECM IMS analytical approach could distinguish LUAD spectral features from spectral features of normal adjacent lung tissue. Conventional liquid chromatography with tandem mass spectrometry (LC-MS/ MS) proteomics demonstrated that specific sites of hydroxylation of proline (HYP) were a main collagen post translational modification that was readily detected in LUAD. A distinct peptide from collagen 3A1 modified by HYP was increased 3.5 fold in lowgrade LUAD compared with normal lung tissue (AUC 0.914, P value <.001). This suggests that regulation of collagen proline hydroxylation could be an important process during early LUAD fibrotic deposition. ECM IMS is a useful tool that may be used to define fibrotic deposition in low-grade LUAD.

Identification of genes with therapeutic and prognostic values in lung adenocarcinoma microenvironment

“…[26]. These results accorded with previous reports on the functions of immune and stromal cells in the TME of LUAD patients [27][28][29].…”

Multiplex Tissue Imaging: Spatial Revelations in the Tumor Microenvironment

“…In parallel, an image is created by combining the data of the spot location with the corresponding measured mass spectrum. In the field of cancer research, MALDI-MSI has been used to analyze drug (metabolite) distribution in the TME, tumor subtyping, tumor grading, or biomarker discovery [55,[76][77][78][79]81]. MALDI-MSI is also used to predict tumor progression and clinical outcomes [56,69].…”

“…For example, elevated collagenase type III levels in the extracellular matrix discriminate low-grade adenocarcinoma (AD) (stage I-III) from adjacent healthy lung tissue. More in-depth analysis revealed that hydroxylated peptides display a specific spatial pattern within the TME, which allows for the differentiation of tumor subtypes [76]. Spatially guided proteomics and histology-guided spatial metabolomics of NSCLC allowed for the differentiation of two NSCLC subtypes: adenocarcinoma and squamous cell carcinoma (SCC).…”

Defining the Tumor Microenvironment by Integration of Immunohistochemistry and Extracellular Matrix Targeted Imaging Mass Spectrometry

“…Tissue was prepared as previously with minor modifications [34,35,43,44]. Previously stained tissues were incubated in xylene for 24-72 h to remove coverslips.…”