Genetic Variations In TLR-4/TIRAP Genes Influence Response To IMiDs-Based Regimens and Conventional Chemotherapy In Patients With Multiple Myeloma
Authors: Bagratuni Tina , Kastritis Efstathios , Eleutherakis-Papaiakovou Evangelos , Kanellias Nikolaos , Liacos Christine , Terpos Evangelos , Dimopoulos Meletios A. 
Published: October 2019

Abstract
The therapeutic efficacy of antimyeloma agents, especially of immunomodulatory drugs (IMiDs), also relies on their ability to influence the tumor-host interaction by modulating immune response, while other agents (chemotherapy, steroids, proteasome inhibitors) may cause significant immunosuppression. Toll like receptors (TLRs) play a central role in the adaptive immune response and TLR-4 signaling involves several intracellular adaptor molecules including MyD88 and Toll/intereukin-1 receptor-associated protein (TIRAP). Germ-line single nucleotide polymorphisms (SNPs) with missense mutations in TLR-4 and TIRAP genes have been associated with susceptibility to infection, autoimmune diseases and inferior outcome in several cancers after chemotherapy or radiotherapy. However, there are no data for multiple myeloma (MM). Thus, we screened 255 patients with MM for the presence of rs4986790 (D299G) and rs4986791 (T399I) SNPs in exons 3 and 4 of TLR4 and rs8177374 (S180L) in exon 5 of TIRAPgene.
Median age of the patients was 66 years (range 31-91 years); 52% were males and 29%, 39% and 32% had ISS-1, -2 & -3, respectively. Median follow up was 40 months. Genetic analysis showed that 8.9% and 8.6% of the patients were heterozygous for the rs4986790 and rs4986791, respectively (there were no homozygous patients for either SNP) and co segregated in 81.5% of the heterozygous patients. For the rs8177374 in TIRAP, 25% were heterozygous and only 1% homozygous for the SNP. There was no segregation of the SNPs in TLR and TIRAP. Frontline therapy was based on IMiDs in 52% of the patients (25% received thalidomide- and 27% lenalidomide-based regimens), while 29.5% received bortezomib-based therapy and 19% conventional chemotherapy (CC). Furthermore, at relapse, 57 patients received lenalidomide-based therapy. Response to primary therapy was attained by 86% of the patients; in 72% of patients treated with CC, in 88% of patients treated with IMiDs and in 89% of patients treated with bortezomib. The presence of the studied SNPs was associated with inferior response to primary therapy (for TLR4, in 60% vs. 88% for rs4986790, p=0.001 and in 66% vs. 87% for rs4986791, p=0.009) but there was no effect of TIRAP SNPs. However, the effect on response was treatment specific. Thus, response to primary therapy with IMiDs was affected by TLR4 SNPs (≥PR in 62% of carriers of rs4986790 vs. 90% of others, p=0.016), was less pronounced in patients treated with CC (p=0.055) and did not affect response to bortezomib (p=0.484). For carriers of the rs4986791, the effect on response to IMiDs was also significant (p=0.05) as well as the effect on patients treated with CC (p=0.022), but again not in patients treated with bortezomib (p=0.424).When both SNPs were present the effect was more pronounced both in patients treated with CC (response in 33% vs. 78%, p=0.022) and in patients treated with IMiDs (63% vs. 90%, p=0.016). In contrary, carriers of the SNP in TIRAP had increased response rates to upfront therapy with CC (100% vs. 66%, p=0.039), but there was no significant effect on response to IMiDs or bortezomib, although there was a trend for inferior PFS in patients treated with bortezomib (p=0.037). Importantly, in multivariate analysis which included the type of primary therapy and the presence of SNPs in TIRAP, the presence of both SNPs in TLR4 was independently associated with lower response probability (p=0.01). The effect of the presence of the above SNPs was different at latter stages of the disease. More specifically, presence of SNPS in TLR4 did not affect response to salvage therapy with lenalidomide for relapsed or refractory disease (p=0.15), but SNPs in TIRAP was associated with low response rates (50% vs. 89%, p=0.002), perhaps as a result of the modulated immune responses due to extensive prior therapy with immunomodulatory and/or immunosuppressive drugs.
This is the first study of the effect of known SNPs in TKR4/TIRAP signaling pathway in patients with MM. Our data indicate that differences in the immune system, due to genetic variability, may be associated with different responses to various therapies and at later stages of the disease, when the immune status of the host is modulated, due to extensive prior therapy with immunosuppressive/immunomodulating agents. Further investigation is needed for the role of the pathways which may regulate the response of the immune system of the host to malignant cells and to immune modulating drugs.

Disclosures:
No relevant conflicts of interest to declare.