Pre-existing autoimmune disease as a risk factor for immune-related adverse events in cancer patients receiving immune checkpoint inhibitors.

Immune checkpoint inhibitors (ICIs) have been widely used as standard therapies for various cancers. However, in 20-30% of cases, ICIs can lead to immune-related adverse events (irAEs), which sometimes require discontinuation of treatment. Due to the increased risk of irAEs, patients with pre-existing autoimmune diseases (AI) are often advised against receiving ICIs. However, there has not been sufficient objective risk assessment for AI. In our study, we conducted logistic regression analysis to assess the risk of irAEs by analyzing 478 cases that received anti-PD-(L)1 Ab and/or anti-CTLA4 Ab at our hospital between April 3, 2017, and May 24, 2022. Among these cases, 28 (5.9%) had pre-existing AI. We selected several independent factors for analysis: gender, age, performance status (PS), cancer type, type of ICI, type of combined anti-cancer agents, best overall response, and pre-existing AI. The adjusted odds ratio (OR) of AI for irAE occurrence was 2.52 [95% CI: 1.08-5.86] (p = 0.033), and the adjusted OR of AI for ICI discontinuation due to irAE was 3.32 [1.41-7.78] (p = 0.006). Patients with pre-existing AI experienced a significantly shorter irAE-free survival time compared to those without AI (median irAE-free survival: 5.7 months [95% CI: 3.5-7.8] vs 10.4 months [95% CI: 7.9-12.9], respectively, p = 0.035). Frequently observed irAEs in full ICI cohort, such as dermatologic issues (7.5%), pneumonitis (7.1%), hepatitis (4.6%), and hypothyroidism (4.2%), were often accompanied by pre-existing AI. Furthermore, pre-existing AI flared up in 6 cases (37.5% in AI-positive irAE-positive cases). The activity of AI was not related to the occurrence of irAEs. Grade 3 or higher irAEs were observed in 6 out of 20 (30.0%) cases in AI-accompanied patients complicated with irAEs. Although having a complicated AI increases the risk of irAEs, it may not necessarily be a contraindication for ICI treatment if closely monitored. (292<300 characters).

Gibberellin-biosynthetic ent-kaurene synthases in higher plants do not require their non-catalytic domains for the catalysis.

ent-Kaurene is a biosynthetic intermediate diterpene of phytohormone gibberellins, and is biosynthesized from geranylgeranyl diphosphate via ent-copalyl diphosphate (ent-CDP). The successive cyclization is catalyzed by two distinct diterpene synthases, ent-CDP synthase (ent-CPS) and ent-kaurene synthase (KS). Homologs of these diterpene synthase genes have been reported to be involved in the biosynthesis of specialized-metabolic diterpenoids for defense in several plant species, including rice (Oryza sativa). These diterpene synthases consist of three domains, αßγ domains. Active sites of ent-CPS exist at the interface of ß and γ domain, while those of KS are located within the α domain. We herein carried out domain-deletion experiments using several KSs and KS like enzymes (KSLs) to obtain insights into the roles of domains other than active-site domains. As previously reported in taxadiene synthase, deletion of γ or ßγ domains drastically decreased activities of specialized-metabolic OsKSL5, OsKSL8, OsKSL7 and OsKSL10 in O. sativa. However, unexpectedly, only α domains of several gibberellin-biosynthetic KSs, including OsKS1 in O. sativa, AtKS in Arabidopsis thaliana, TaKS in wheat (Triticum aestivum) and BdKS1 in Brachypodium distachyon, retained their original functions. Additionally, the specialized-metabolic OsKSL4, which is closely related to OsKS1, also functioned without its ßγ domains. Domain-swapping experiments showed that replacing ßγ domains in OsKSL7 with those from other KS/KSLs retained the OsKSL7 activity. Moreover, deletion of ßγ domains of bifunctional PpCPS/KS in moss (Physcomitrella patens) drastically impaired its KS-related activity. Thus, we demonstrate that monofunctional gibberellin-biosynthetic KSs are the unique diterpene synthases that retain their functions without ßγ domains.

Essential residues in diterpene synthases for biosynthesis of oryzalexins A-F in rice phytoalexin.

Cultivated rice (Oryza sativa) produces a variety of diterpenoid-type phytoalexins. Diterpene synthase genes that are responsible for the biosynthesis of momilactones, phytocassanes, and oryzalexins have been identified in O. sativa cv. Nipponbare. OsKSL10 (Os12t0491800 in RAP and LOC_Os12g30824 in MSU) was previously identified as an enzyme catalyzing the conversion of ent-copalyl diphosphate to ent-sandaracopimaradiene for the production of oryzalexins A to F. Our previous study on Oryza rufipogon, a wild progenitor of Asian cultivated rice, showed that both OrKSL10 and OrKSL10ind from O. rufipogon accessions W1943 and W0106, respectively, closely related to the japonica and indica subspecies, converted ent-copalyl diphosphate to ent-miltiradiene. Thus, the functional conversion of ent-miltiradiene synthase into ent-sandaracopimaradiene synthase is implied to have occurred through natural amino acid mutations, the details of which have not been elucidated. In this study, we show that introduction of A654G substitution into OrKSL10 significantly alters its function into more closely resembling that of OsKSL10. Moreover, double substitution V546I/A654G almost completely converts the function of OrKSL10 into that of OsKSL10. On the other hand, the reversed substitution I546V/G654A was insufficient to convert the function of OsKSL10 into OrKSL10, indicating the introduction of additional substitution S522I is required for the functionality of OsKSL10. Lastly, point mutations at the 654A residue in OrKSL10 suggest that hydrophobic side chains at this position have a negative influence on the production of ent-sandaracopimaradiene.