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The proteins of extracellular vesicles (EVs) that originate from tumors reflect the producer cells' proteomes and can be detected in biological fluids. Thus, EVs provide proteomic signatures that are of great interest for screening and predictive cancer diagnostics. By applying targeted mass spectrometry with stable isotope-labeled peptide standards, we assessed the levels of 28 EV-associated proteins, including the conventional exosome markers CD9, CD63, CD81, CD82, and HSPA8, in vesicles derived from the lung cancer cell lines NCI-H23 and A549. Furthermore, we evaluated the detectability of these proteins and their abundance in plasma samples from 34 lung cancer patients and 23 healthy volunteers. The abundance of TLN1, TUBA4A, HSPA8, ITGB3, TSG101, and PACSIN2 in the plasma of lung cancer patients was measured using targeted mass spectrometry and compared to that in plasma from healthy volunteers. The most diagnostically potent markers were TLN1 (AUC, 0.95), TUBA4A (AUC, 0.91), and HSPA8 (AUC, 0.88). The obtained EV proteomic signature allowed us to distinguish between the lung adenocarcinoma and squamous cell carcinoma histological types. The proteomic cargo of the extracellular vesicles represents a promising source of potential biomarkers.

In the present study, we applied selected reaction monitoring (SRM) to a group of proteins that were previously reported to be associated with lung cancer (Novikova S.E. et al. (2017) Biomeditsinskaya khimiya, 63, 181-210. [1]). Measurements were performed on 59 plasma samples. These samples included: 23 samples of plasma of patients diagnosed with lung adenocarcinoma (LAC), 11 samples of plasma of patients diagnosed with squamous cell lung carcinoma (SqCC), 25 samples of donors with no previous history of oncological diseases, and one pooled sample from each of the above group. As a result of the SRM measurements 52 proteins were detected at least in one individual plasma sample. Statistical analysis showed that there were two groups confidently differentiated by the concentration value of 8 proteins wherein 5 proteins displayed increased level (P00738, P26639, P21926, P08603, P51149) in LAC group and 3 proteins (P51884, O15162, Q8N2K0) indicated diminishing the concentration level towards the control level. Data on protein concentrations obtained for LAC and SqCC did not distinguish the samples by statistical clustering analysis. These potential biomarkers can be used for further development of methods for early diagnostics of lung cancer.

To date lung adenocarcinoma (LAC) is the most common type of lung cancer. Numerous studies on LAC biology resulted in identification of crucial mutations in protooncogenes and activating neoplastic transformation pathways. Therapeutic approaches that significantly increase the survival rate of patients with LAC of different etiology have been developed and introduced into clinical practice. However, the main problem in the treatment of LAC is early diagnosis, taking into account both factors and mechanisms responsible in tumor initiation and progression. Identification of a wide biomarker repertoire with high specificity and reliability of detection appears to be a solution to this problem. In this context, proteins with differential expression in normal and pathological condition, suitable for detection in biological fluids are the most promising biomarkers. In this review we have analyzed literature data on studies aimed at search of LAC biomarkers. The major attention has been paid to protein biomarkers as the most promising and convenient subject of clinical diagnosis. The review also summarizes existing knowledge on posttranslational modifications, splice variants, isoforms, as well as model systems and transcriptome changes in LAC.