Abstract
BackgroundTreatment with Bacillus Calmette-Guérin (BCG) is the gold standard adjuvant immunotherapy of non-muscle invasive bladder cancer (NMIBC), although it fails in one third of the patients. NMIBC expresses two tumor-associated O-linked carbohydrates: the disaccharide (Galβ1,3GalNAc) Thomsen-Friedenreich (T) antigen, and its sialylated counterpart (Siaα2,3Galβ1,3GalNAc) sialyl-T (sT), synthesized by sialyltransferase ST3GAL1, whose roles in BCG response are unknown.MethodsThe human bladder cancer (BC) cell line HT1376 strongly expressing the T antigen, was retrovirally transduced with the ST3GAL1 cDNA or with an empty vector, yielding the cell lines HT1376sT and HT1376T, that express, respectively, either the sT or the T antigens. Cells were in vitro challenged with BCG. Whole gene expression was studied by microarray technology, cytokine secretion was measured by multiplex immune-beads assay. Human macrophages derived from blood monocytes were challenged with the secretome of BCG-challenged BC cells.ResultsThe secretome from BCG-challenged HT1376sT cells induced a stronger macrophage secretion of IL-6, IL-1β, TNFα and IL-10 than that of HT1376T cells. Transcriptomic analysis revealed that ST3GAL1 overexpression and T/sT replacement modulated hundreds of genes. Several genes preserving genomic stability were down-regulated in HT1376sT cells which, as a consequence, displayed increased sensitivity to oxidative damage. After BCG challenge, the transcriptome of HT1376sT cells showed higher susceptibility to BCG modulation than that of HT1376T cells.ConclusionsHigh ST3GAL1 expression and T/sT replacement in BCG challenged-BC cancer cells induce a stronger macrophage response and alter the gene expression towards genomic instability, indicating a potential impact on BC biology and patient’s response to BCG.
Highlights
Treatment with Bacillus Calmette-Guérin (BCG) is the gold standard adjuvant immunotherapy of nonmuscle invasive bladder cancer (NMIBC), it fails in one third of the patients
We investigated the effects of the alternative expression of the T or sT antigens on the ability of BC cells to activate macrophages in response to BCG challenge and on the transcriptome of BC cells, utilizing the HT1376 cell line in which the T antigen was replaced by the sT antigen, by retroviral transduction with the ST3GAL1 cDNA
Antigen in HT1376 cells The mock-transduced cell line HT1376T, like the wild type HT1376, expressed high and homogeneous T expression, while the ST3GAL1-transduced cell line HT1376sT displayed an homogeneous low Peanut agglutinin (PNA) reactivity which could be reverted to high reactivity after sialidase treatment (Additional file 1B)
Summary
Treatment with Bacillus Calmette-Guérin (BCG) is the gold standard adjuvant immunotherapy of nonmuscle invasive bladder cancer (NMIBC), it fails in one third of the patients. NMIBC expresses two tumorassociated O-linked carbohydrates: the disaccharide (Galβ1,3GalNAc) Thomsen-Friedenreich (T) antigen, and its sialylated counterpart (Siaα2,3Galβ1,3GalNAc) sialyl-T (sT), synthesized by sialyltransferase ST3GAL1, whose roles in BCG response are unknown. The intravesical inoculation with the Bacillus CalmetteGuérin (BCG) is the most effective adjuvant therapy of non-muscle invasive bladder cancers (NMIBC) after transurethral resection. The sialyl-T (sT) (Siaα2,3Galβ1,3GalNAc-O-Ser/Thr) structure and its main biosynthetic enzyme, the sialyltransferase ST3GAL1, are aberrantly expressed in a variety of cancers [17, 18] [reviewed in [19, 20]]. The T antigen has been suggested as a useful marker of BCG response [23], even though the relationship between ST3GAL1/sT and BCG response has never been established
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