DNA demethylation and tri-methylation of H3K4 at the TACSTD2 promoter are complementary players for TROP2 regulation in colorectal cancer cells

TROP2 is a powerful cancer driver in colorectal cancer cells. Divergent epigenetic regulation mechanisms for the corresponding TACSTD2 gene exist such as miRNAs or DNA methylation. However, the role of TACSTD2 promoter hypermethylation in colorectal cancer has not been investigated yet. In this study, TROP2 expression strongly correlated with promoter methylation in different colorectal tumor cell lines. Treatment with 5-Azacytidine, a DNMT1 inhibitor, led to demethylation of the TACSTD2 promoter accompanied by an increase in TROP2 protein expression. TROP2 expression correlated with promoter methylation in vivo in human colon tumor tissue, thereby verifying promoter methylation as an important factor in the regulation of TROP2 expression in colorectal cancer. When performing a ChIP-Seq analysis in HCT116 and HT29 cells, we found that TACSTD2 promoter demethylation was accompanied by tri-methylation of H3K4. In silico analysis of GSE156613 data set confirmed that a higher binding of histone mark H3K4me3 around the TACSTD2 promoter was found in TACSTD2 high expressing tumors of colon cancer patients compared to the corresponding adjacent tumor tissue. Moreover, the link between TROP2 and the H3K4me3 code was even evident in tumors showing high intratumoral heterogeneity for TROP2 staining. Our data provide novel evidence for promoter demethylation and simultaneous gains of the active histone mark H3K4me3 across CpG-rich sequences, both being complementary mechanisms in the transcriptional regulation of TACSTD2 in colon cancer. The functional consequences of TROP2 loss in colorectal cancer needs to be further investigated.

Complementary effects of HDAC inhibitor 4-PB on gap junction communication and cellular export mechanisms support restoration of chemosensitivity of PDAC cells

Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease and one of the cancer entities with the lowest life expectancy. Beside surgical therapy, no effective therapeutic options are available yet. Here, we show that 4-phenylbutyrate (4-PB), a known and well-tolerable inhibitor of histone deacetylases (HDAC), induces up to 70% apoptosis in all cell lines tested (Panc 1, T4M-4, COLO 357, BxPc3). In contrast, it leads to cell cycle arrest in only half of the cell lines tested. This drug increases gap junction communication between adjacent T3M-4 cells in a concentration-dependent manner and efficiently inhibits cellular export mechanisms in Panc 1, T4M-4, COLO 357 and BxPc3 cells. Consequently, in combination with gemcitabine 4-PB shows an overadditive effect on induction of apoptosis in BxPc3 and T3M-4 cells (up to 4.5-fold compared to single drug treatment) with accompanied activation of Caspase 8, BH3 interacting domain death agonist (Bid) and poly (ADP-ribose) polymerase family, member 1 (PARP) cleavage. Although the inhibition of the mitogen-activated protein kinase-pathway has no influence on fulminant induction of apoptosis, the inhibition of the JNK-pathway by SP600125 completely abolishes the overadditive effect induced by the combined application of both drugs, firstly reported by this study.

Agonistic and antagonistic interactions of anti-interleukin 2 receptor monoclonal antibodies in rat recipients of cardiac allografts

A panel of five mouse mAbs recognizing 4 distinct epitopes (R1-4) of the rat 55kD IL-2R molecule were tested for their influence on acute rejection (8 days) of (LEWxBN)F1 cardiac allografts in LEW hosts. IL-2R1 targeted therapy with ART-18 (IgG1, inhibits IL-2-dependent responses) prolonged graft survival to ca.21 days. IL-2R2 is recognized by ART-65 and ART-75, mAbs that do not inhibit T cell growth. Treatment with ART-65 (IgG1) but not ART-75 (IgG2a) abrogated acute rejection (ca. 16 days and 9 days, respectively). ART-35, an anti-IL-2R3 mAb (IgG1, does not inhibit T cell function) extended graft survival marginally to ca. 12 days. Finally, therapy with OX-39, (anti-R4 IgG1 mAb, inhibits IL-2 binding, but not IL-2-driven growth) was completely ineffectual. Simultaneous targeting of two IL-2R epitopes increased the therapeutic index synergistically (ART-18 [R1] + ART-65 [R2]--60% permanent graft acceptance), additively (ART-75 [R1] + ART-35 [R3]--graft survival ca. 18 days), or did not improve further graft survival at all (ART-18 [R1] + OX-39 [R4]--graft survival ca. 18 days). Thus, the cellular targeting patterns and isotype of mAbs are crucial: (1) targeting at functionally distinct epitopes controls rejection most effectively; (2) IgG1 and IgG2b mAbs are more influential in vivo than IgG2a, data supported by the studies employing the family of ART-18 isotype switch variants. Treatment with anti-IL-2R mAb did not depress Ts activity as tested both in vitro and in vivo. Sparing of putative Ts by mAb is also shown by thymectomy of graft recipients before or during ART-18 therapy, which shortened graft survival to 13-15 days; thymectomy after ART-18 therapy did not influence graft survival. However, infusion of IFN-gamma recreated classic acute rejection within 10 days in otherwise longstanding cardiac allografts in ART-18 treated hosts. Upregulation of MHC class II antigen and IL-2R expression seems to be primarily responsible for this striking biological effect of IFN-gamma in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)