Olfactory receptor 5B21 drives breast cancer metastasis

Pan-cancer analysis identifies olfactory receptor family 7 subfamily A member 5 as a potential biomarker for glioma

Background

Human olfactory receptors (ORs) account for approximately 60% of all human G protein-coupled receptors. The functions of ORs extend beyond olfactory perception and have garnered significant attention in tumor biology. However, a comprehensive pan-cancer analysis of ORs in human cancers is lacking.

Methods

Using data from public databases, such as HPA, TCGA, GEO, GTEx, TIMER2, TISDB, UALCAN, GEPIA2, and GSCA, this study investigated the role of olfactory receptor family 7 subfamily A member 5 (OR7A5) in various cancers. Functional analysis of OR7A5 in LGG and GBM was performed using the CGGA database. Molecular and cellular experiments were performed to validate the expression and biological function of OR7A5 in gliomas.

Results

The results revealed heightened OR7A5 expression in certain tumors, correlating with the expression levels of immune checkpoints and immune infiltration. In patients with gliomas, the expression levels of OR7A5 were closely associated with adverse prognosis, 1p/19p co-deletion status, and wild-type IDH status. Finally, in vitro experiments confirmed the inhibitory effect of OR7A5 knockdown on the proliferative capacity of glioma cells and on the expression levels of proteins related to lipid metabolism.

Conclusion

This study establishes OR7A5 as a novel biomarker, potentially offering a novel therapeutic target for gliomas.

The structure and function of olfactory receptors

Olfactory receptors (ORs) form the most important chemosensory receptor family responsible for our sense of smell in the nasal olfactory epithelium. This receptor family belongs to the class A G protein-coupled receptors (GPCRs). Recent research has indicated that ORs are involved in many nonolfactory physiological processes in extranasal tissue, such as the brain, pancreas, and testes, and implies the possible role of their dysregulation in various diseases. The recently released structures of OR51E2 and consensus OR52 have also unveiled the uniqueness of ORs from other class A GPCR members. In this review, we discuss these recent developments and computational modeling efforts toward understanding the structural properties of unresolved ORs, which could guide potential future OR-targeted drug discovery.

The Expression of Trace Amine-Associated Receptors (TAARs) in Breast Cancer Is Coincident with the Expression of Neuroactive Ligand-Receptor Systems and Depends on Tumor Intrinsic Subtype

Currently, the contribution of trace amine-associated receptors (TAARs) to breast cancer (BC) is recognized, but their associations with various pathological characteristics are not yet understood. There is accumulated transcriptomic data for BC tumors, which are represented in publicly accessible databases. We estimated TAARs' (including TAAR1, TAAR2, TAAR5, TAAR6, TAAR8, and TAAR9) associations with BC stage, grade, and molecular subtypes in these data and identified that the expression of all TAARs was associated with more unfavorable cancer subtypes, including basal-like and HER2-positive tumors. Also, the significant upregulation of all TAARs was demonstrated in circulating tumor cells compared to the metastatic lesions. Considering that co-expressed genes are more likely to be involved in the same biologic processes, we analyzed genes that are co-expressed with TAARs in BC. These gene sets were enriched with the genes of the olfactory transduction pathway and neuroactive ligand-receptor interaction participants. TAARs are co-expressed with G-protein-coupled receptors of monoamine neurotransmitters including dopamine, norepinephrine, and serotonin as well as with other neuroactive ligand-specific receptors. Since TAAR1 is able to modulate the activity of monoamine receptors that are involved in the regulation of BC growth, TAAR1 and potentially other TAARs may be regarded as prospective therapeutic targets for breast cancer.

Large-scale assessment of pros and cons of autopsy-derived or tumor-matched tissues as the norms for gene expression analysis in cancers

Normal tissues are essential for studying disease-specific differential gene expression. However, healthy human controls are typically available only in postmortal/autopsy settings. In cancer research, fragments of pathologically normal tissue adjacent to tumor site are frequently used as the controls. However, it is largely underexplored how cancers can systematically influence gene expression of the neighboring tissues. Here we performed a comprehensive pan-cancer comparison of molecular profiles of solid tumor-adjacent and autopsy-derived "healthy" normal tissues. We found a number of systemic molecular differences related to activation of the immune cells, intracellular transport and autophagy, cellular respiration, telomerase activation, p38 signaling, cytoskeleton remodeling, and reorganization of the extracellular matrix. The tumor-adjacent tissues were deficient in apoptotic signaling and negative regulation of cell growth including G2/M cell cycle transition checkpoint. We also detected an extensive rearrangement of the chemical perception network. Molecular targets of 32 and 37 cancer drugs were over- or underexpressed, respectively, in the tumor-adjacent norms. These processes may be driven by molecular events that are correlated between the paired cancer and adjacent normal tissues, that mostly relate to inflammation and regulation of intracellular molecular pathways such as the p38, MAPK, Notch, and IGF1 signaling. However, using a model of macaque postmortal tissues we showed that for the 30 min - 24-hour time frame at 4ºC, an RNA degradation pattern in lung biosamples resulted in an artifact "differential" expression profile for 1140 genes, although no differences could be detected in liver. Thus, such concerns should be addressed in practice.

Molecular genetic and clinical characteristic analysis of primary signet ring cell carcinoma of urinary bladder identified by a novel OR2L5 mutation

To get a better understanding of the genetic basis of primary signet ring cell carcinoma (SRCC) of the bladder, which is highly rare and not yet explored. First, by using immunohistochemistry to find histological pathological characteristics. Second, a massively parallel whole-exome sequencing (WES) was performed on a 58-year-old male patient who had painless macroscopic hematuria and was pathologically diagnosed with primary SRCC of the bladder, followed by comparing with genes of ordinary urothelial cancer (UC) from TCGA. Furthermore, a population-based analysis using the SEER database was performed to investigate the prognosis (SRCC vs. UC). We identified 63 copy number variations (CNVs) with gain counts and 181 CNVs with loss counts. Totally 4515 mutations were discovered in C > T with a success rate of greater than 89%. The most frequently mutated pathway was RTK-RAS which has 85 genes involved in carcinogenic signaling. Final screening on predisposing genes is performed after filtering based on ACMG. Moreover, several driver genes, including NBN, KCTD18, SPATA13, ANKRD36, OR2L5, MALRD1, and LSMEM1, were detected. Sanger sequencing of germline DNA revealed the presence of a mutant base A/G of OR2L5 in the sequence, which was discovered for the first time in primary SRCC of the bladder. Furthermore, the immunohistochemical profile showed that primary SRCC of the bladder were positive for CK7, CK20, GATA-3, and expression of CK(AE1/AE2), EMA, and Ki67. In the SEER-based study, the patients with primary SRCC of the bladder got a worse prognosis compared to those with UC with median months overall survival (OS) 14 vs. 41, respectively, P = 0001, even after adjusting the variables in the Cox regression model, the SRCC of the bladder showed worse survival HR = 1.119, 95% CI = (1.081-1.328), P = 0.0001. These results imply that suppression of potential driver mutations may be a viable adjuvant treatment approach for primary SRCC in the bladder in place of standard chemotherapy, a possibility that warrants further clinical investigation.