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Background: Patients with brain metastases (BMs) have a poor prognosis and limited therapeutic options. Lung cancer is the most common primary malignancy giving rise to BMs; thus, understanding the molecular mechanisms behind increased BM risk is essential for identifying therapeutic targets and developing effective interventions.Methods: Sixty-one patients who underwent surgical resection of primary non-small cell lung cancer (NSCLC) and BMs were retrospectively studied. Comprehensive genomic profiling of primary NSCLC and matched BMs was performed with next-generation sequencing targeting 416 cancer-relevant genes.Results: Mutations of major drivers, including EGFR, KRAS, TP53, and ALK, were highly concordant between primary NSCLC and matched BMs (>80%), whereas discordance suggested the unique genomic evolution and oncogenic mechanisms of NSCLC BMs. BMs also demonstrated higher levels of copy number variations in comparison with primary NSCLC. Furthermore, the alterations of genes encoding CDK4/CCND1, CDKN2A/2B, and PI3K signaling pathways were enriched in BMs, and this suggested their correlation with increased metastatic risk. Indeed, patients with activated PI3K signaling in their primary NSCLC had significantly shorter BM-free survival (hazard ratio, 8.49; P = .0005). In addition, mutated TP53 or an activated WNT pathway via CTNNB1, APC, and AXIN2 mutations trended toward shorter BM-free intervals but not significantly so.Conclusions: These findings yield detailed insights into the genomic complexity and heterogeneity of primary NSCLC and matched BMs. This study highlights the significant correlation of PI3K signaling with increased metastatic risk in patients with NSCLC and identifies genomic alterations enriched in NSCLC BMs that could serve as prognostic markers and potential therapeutic targets for treating patients with NSCLC BMs. [ABSTRACT FROM AUTHOR]

Background and Purpose: The cannabinoid CB(1) receptor is primarily thought to be functionally coupled to the G(i) form of G proteins, through which it negatively regulates cAMP accumulation. Here, we investigated the dual coupling properties of CB(1) receptors and characterized the structural determinants that mediate selective coupling to G(s) and G(i).Experimental Approach: A cAMP-response element reporter gene system was employed to quantitatively analyze cAMP change. CB(1)/CB(2) receptor chimeras and site-directed mutagenesis combined with functional assays and computer modelling were used to determine the structural determinants mediating selective coupling to G(s) and G(i).Key Results: CB(1) receptors could couple to both G(s)-mediated cAMP accumulation and G(i)-induced activation of ERK1/2 and Ca(2+) mobilization, whereas CB(2) receptors selectively coupled to G(i) and inhibited cAMP production. Using CB(1)/CB(2) chimeric receptors, the second intracellular loop (ICL2) of the CB(1) receptor was identified as primarily responsible for mediating G(s) and G(i) coupling specificity. Furthermore, mutation of Leu-222 in ICL2 to either Ala or Pro switched G protein coupling from G(s) to G(i), while to Ile or Val led to balanced coupling of the mutant receptor with G(s) and G(i) .Conclusions and Implications: The ICL2 of CB(1) receptors and in particular Leu-222, which resides within a highly conserved DRY(X)(5) PL motif, played a critical role in G(s) and G(i) protein coupling and specificity. Our studies provide new insight into the mechanisms governing the coupling of CB(1) receptors to G proteins and cannabinoid-induced tolerance. [ABSTRACT FROM AUTHOR]