Ionizing radiation improves skin bacterial dysbiosis in cutaneous T-cell lymphoma

Abstract

Introduction: Cutaneous T-cell lymphoma (CTCL) is closely associated with the host microbiome. While recent evidence suggests that shifts in specific bacterial taxa are associated with response to UV-B, a form of non-ionizing radiation, the impact of ionizing radiation (IR) has not been investigated.

Methods: 16S rRNA and tuf gene amplicon sequencing were performed on DNA extracted from swabs of lesional/non-lesional skin of 12 CTCL patients before/after TSEBT or local IR and from 25 matched healthy controls (HC). Microbial diversity and taxonomic profiles were analyzed.

Results: Radiation exposure increased CTCL skin α-diversity to levels approximating HC. TSEBT appeared to carry the greatest effect compared to local IR. Both α and β-diversity differed significantly post versus pre-IR for TSEBT, but not for local IR. IR was associated with decreases in known pathogenic bacteria such as Streptococcus and S. aureus and increases in healthy commensal bacteria such as Anaerococcus, Bifidobacterium and commensal staphylococci including S. pettenkoferi. Substantially more taxa shifts were seen with TSEBT versus local IR.

Discussion: IR not only eliminates CTCL lesions via induction of apoptosis, but also facilitates skin barrier restoration and recolonization of bacterial taxa associated with a healthy skin microbiome. Local IR does not have as strong an effect on the skin microbiome as TSEBT. As skin microbiota act as immunomodulators with local and potentially systemic influence, TSEBT may also improve CTCL lesions via global effects on the skin microbiome. Future larger-scale studies are required to fully elucidate the relationship between cutaneous microbes and IR treatment in CTCL.

Keywords: cutaneous T-cell lymphoma; lymphoma; microbiome; radiation; radiotherapy; skin cancer; total skin electron beam therapy.

Figure 1

Taxon-by-taxon and α- and β-diversity analyses for skin exposed to any form of ionizing radiation (IR). (A) At the taxonomic level of genus, Staphylococcus, Corynebacterium, and Streptococcus were the most prevalent and abundant genera amongst all samples. Bar charts indicate the relevant abundance of the 19 most abundant genera, remaining genera were grouped as “other.” (B) For any skin (both lesional & non-lesional) exposed to any form of IR, α-diversity is higher with IR exposure, and β-diversity is significantly different between the two communities. (C) For only lesional skin exposed to IR, α- and β-diversities are not significantly different between skin with and without IR exposure. (D) For non-lesional skin exposed to any form of radiotherapy, α-diversity and β-diversity were significantly different between skin with and without IR exposure. (E) Taxa-by-taxa analyses with and without IR exposure reveals significantly different relative abundances of specific bacterial taxa. *p <0.05; **p<0.01; ***p<0.001; ns, not significant.

Figure 2

α- and β-diversity analyses for the TSEBT and local-IR study groups analyzed. (A) Analyses of both lesional and non-lesional skin before and after TSEBT demonstrates higher α-diversity post-TSEBT for both groups. There was no significant difference in α-diversity between lesional and non-lesional skin at either pre-TSEBT or post-TSEBT time points. (B) β-diversity for lesional and non-lesional skin reveals different microbial communities for pre- versus post-TSEBT but not between lesional and non-lesional skin at pre-TSEBT and post-TSEBT timepoints. (C) Analyses of α-diversity amongst local IR samples demonstrate no change with treatment or between lesional and non-lesional samples. (D) There were no differences in β-diversity between pre and post-local IR for either lesional or non-lesional samples, or between lesional and non-lesional samples at either pre-local IR or post-local IR timepoints. *p <0.05; **p<0.01; ns, not significant.

Figure 3

Taxon-by-taxon analyses amongst pre versus post-TSEBT skin and lesional versus non-lesional skin. (A) Analysis of lesional skin before TSEBT reveals increased relative abundance of Streptococcus and Roseomonas and other potentially pathogenic skin genera pre-TSEBT, and increases in the relative abundance of multiple anti-inflammatory taxa post-TSEBT. (B) Analysis of non-lesional skin reveals increased relative abundance of Rothia and other inflammatory taxa pre-TSEBT and increases in healthy commensals Bifidobacterium, S. caprae, and S. pettenkoferi post-TSEBT. (C) Species level Staphylococcus analyses of lesional versus non-lesional skin before TSEBT reveals increases in multiple taxa, including S. aureus. (D) Analysis of lesional skin reveals decrease in pathogenic Kytococcus and Turicella post-local IR compared to pre-local IR. The black line represents mean relative abundance. *p <0.05; **p<0.01; ***p<0.001; ****p<0.0001.

Figure 4

Healthy controls (HC) skin compared to CTCL skin before and after any form of IR and before and after TSEBT. (A) α-diversity was significantly lower in pre-IR patients than HC, and β-diversity differed significantly between the groups. (B) After any form of IR, CTCL skin α-diversity was no longer lower than that of HC, but β-diversities remained significantly different. (C) α-diversity was significantly lower in pre-TSEBT compared to HC skin, and β-diversity differed significantly between the groups. (D) Post-TSEBT α-diversity was no longer significantly different compared to HC but β-diversity remained different between post-TSEBT patients and HC. **p<0.01; ***p<0.001; ns, not significant.