1179 Gut microbial profiles may predict narrowband ultraviolet B response in cutaneous T cell lymphoma patients

Despite strong evidence that gut microbiota can influence immunity and tumor microenvironments, the functional relationship between the gut microbiome and cutaneous T cell lymphoma (CTCL), a cancer associated with global dysbiosis, is unclear. Further, the effect of narrowband UVB (nbUVB) on the CTCL gut microbiome remains unexplored. Our team previously demonstrated CTCL patients harbor altered gut microbiomes and their skin microbiota may carry predictive signals for nbUVB response. Here, we used 16S sequencing to examine the gut microbiota of 14 nbUVB-treated CTCL patients (12 mycosis fungoides/Sezary syndrome, 2 other CTCL; 7 responders (R), 7 non-responders (NR)). Pre- versus post-nbUVB and R versus NR analyses showed no significant differences in α- and β-diversity. However, taxon-by-taxon analysis revealed abundance differences in Bacteroidaceae, Ruminococcaceae, and Eggerthellaceae that trended towards significance (p<0.05, q>0.05). A promoter of IL-17-mediated inflammation, Bacteroidaceae communities were more abundant pre-nbUVB in eventual NR versus R, but Ruminicococaceae, a short chain fatty acid producer with anti-inflammatory activity, was more abundant in R. These findings suggest gut microbiota may contain biomarkers for nbUVB responsiveness in CTCL. Post-nbUVB, Eggerthellaceae abundance was greater in R than NR. As we previously showed, Eggerthellaceae was significantly reduced in the guts of CTCL patients with higher skin disease burden, these new data emphasize potential influence of the gut microbiome in modulating CTCL disease activity. These trends are consistent with our prior work and accepted literature on the CTCL gut microbiome, although power likely affected the statistical significance of these data. Still, exploring such microbial patterns will be important as we continue to unlock the relationship between the gut microbiome and CTCL.