Radiation-response in primary fibroblasts of long-term survivors of childhood cancer with and without second primary neoplasms: the KiKme study
Authors: Grandt Caine Lucas , Brackmann Lara Kim , Poplawski Alicia , Schwarz Heike , Hummel-Bartenschlager Willempje , Hankeln Thomas , Kraemer Christiane , Marini Federico , Zahnreich Sebastian , Schmitt Iris , Drees Philipp , Mirsch Johanna , Grabow Desiree , Schmidberger Heinz , Binder Harald , Hess Moritz , Galetzka Danuta , Marron Manuela 
Published: September 2022

Background

The etiology and most risk factors for a sporadic first primary neoplasm in childhood or subsequent second primary neoplasms are still unknown. One established causal factor for therapy-associated second primary neoplasms is the exposure to ionizing radiation during radiation therapy as a mainstay of cancer treatment. Second primary neoplasms occur in 8% of all cancer survivors within 30 years after the first diagnosis in Germany, but the underlying factors for intrinsic susceptibilities have not yet been clarified. Thus, the purpose of this nested case–control study was the investigation and comparison of gene expression and affected pathways in primary fibroblasts of childhood cancer survivors with a first primary neoplasm only or with at least one subsequent second primary neoplasm, and controls without neoplasms after exposure to a low and a high dose of ionizing radiation.

Methods

Primary fibroblasts were obtained from skin biopsies from 52 adult donors with a first primary neoplasm in childhood (N1), 52 with at least one additional primary neoplasm (N2+), as well as 52 without cancer (N0) from the KiKme study. Cultured fibroblasts were exposed to a high [2 Gray (Gy)] and a low dose (0.05 Gy) of X-rays. Messenger ribonucleic acid was extracted 4 h after exposure and Illumina-sequenced. Differentially expressed genes (DEGs) were computed usinglimmafor R, selected at a false discovery rate level of 0.05, and further analyzed for pathway enrichment (right-tailed Fisher’s Exact Test) and (in-) activation (z ≥|2|) usingIngenuity Pathway Analysis.

Results

After 0.05 Gy, least DEGs were found in N0 (n = 236), compared to N1 (n = 653) and N2+ (n = 694). The top DEGs with regard to the adjustedp-value were upregulated in fibroblasts across all donor groups (SESN1,MDM2,CDKN1A,TIGAR,BTG2,BLOC1S2,PPM1D,PHLDB3,FBXO22,AEN,TRIAP1, andPOLH). Here, we observed activation ofp53 Signalingin N0 and to a lesser extent in N1, but not in N2+. Only in N0, DNA (excision-) repair (involved genes:CDKN1A,PPM1D, andDDB2) was predicted to be a downstream function, while molecular networks in N2+ were associated with cancer, as well as injury and abnormalities (among others, downregulation ofMSH6,CCNE2, andCHUK). After 2 Gy, the number of DEGs was similar in fibroblasts of all donor groups and genes with the highest absolute log2fold-change were upregulated throughout (CDKN1A, TIGAR, HSPA4L,MDM2,BLOC1SD2,PPM1D,SESN1,BTG2,FBXO22,PCNA, andTRIAP1). Here, thep53 Signaling-Pathway was activated in fibroblasts of all donor groups. TheMitotic Roles of Polo Like Kinase-Pathway was inactivated in N1 and N2+.Molecular Mechanisms of Cancerwere affected in fibroblasts of all donor groups.P53was predicted to be an upstream regulator in fibroblasts of all donor groups andE2F1in N1 and N2+. Results of the downstream analysis weresenescencein N0 and N2+,transformation of cellsin N0, and no significant effects in N1. Seven genes were differentially expressed in reaction to 2 Gy dependent on the donor group (LINC00601,COBLL1,SESN2,BIN3,TNFRSF10A,EEF1AKNMT, andBTG2).

Conclusion

Our results show dose-dependent differences in the radiation response between N1/N2+ and N0. While mechanisms against genotoxic stress were activated to the same extent after a high dose in all groups, the radiation response was impaired after a low dose in N1/N2+, suggesting an increased risk for adverse effects including carcinogenesis, particularly in N2+.