Berlit, S. | Search bioRxiv

bioRxiv2025

Interplay between BET Proteins and the Pre-Replication Complex Unveils Therapeutic Vulnerabilities in Cancer

Replication stress is a critical event in cancer development and understanding the underlying molecular mechanisms can help to identify new treatment strategies. Here, we investigate the molecular interplay between the pre-replication complex (pre-RC) and the bromodomain and extraterminal domain (BET) proteins in orchestrating replication stress response. Our findings reveal a mutual dependency between BET proteins and the pre-RC within cancer cells. Notably, reduction in origin licensing or replication initiation makes cells more susceptible to the BET-inhibitor AZD5153. Furthermore, we observe synergistic effects when combining the CDC7 inhibitor XL413 with AZD5153, effects which were partly dependent on TP53 mutation status. This combination treatment results in unresolved DNA damage and R-loop formation, leading to increased genomic instability. These insights pave the way for novel strategies for targeted cancer therapies and provide a foundation for further investigation into the interplay between CDC7 and BET proteins in replication stress response. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=194 SRC="FIGDIR/small/645172v2_ufig1.gif" ALT="Figure 1"> View larger version (85K): org.highwire.dtl.DTLVardef@f5b170org.highwire.dtl.DTLVardef@545fbeorg.highwire.dtl.DTLVardef@159b631org.highwire.dtl.DTLVardef@c851cf_HPS_FORMAT_FIGEXP M_FIG C_FIG The graphic illustrates how the CDC7 inhibitor XL413 and the BET inhibitor AZD5153 work together in TP53-deficient cancer cells. First, XL413 prevents activation of the origin of replication complex, leading to DNA damage. Second, the DNA repair machinery is unable to resolve this damage, resulting in the accumulation of unresolved R-loops and genomic instability. Ultimately, this cascade culminates in cell death.

cancer biology↗

bioRxiv2023

Inhibition of Replication Origins and ATR Synergistically Activates the Innate Immune System in Cancer Cells

Sufficient numbers of activated replication origins are essential for successful DNA replication. While normal cells load replication origins in abundance to the genome, cancer cells often load fewer origins of replication due to genomic alterations such as CCNE1 amplifications. Here we exploit this feature to sensitize cancer cells to ATR inhibition. We show by using siRNA and small molecules that the inhibition of origin activation as well as the reduction of replication origins itself sensitizes ovarian cancer cell lines against ATR inhibition by inducing genomic instability. We further show that in ovarian cancer cells this combinatorial approach leads to an increased genomic instability which manifests in an increase of micronuclei that consequently activate the innate immune system through the cGAS-STING pathway. Notably, no activation of the innate immune system was observed in immortalized fallopian tube cells. However, overexpression of Cyclin E1 in this model leads to a marked increase in genomic instability and innate immune activation. Here we provide preclinical evidence to increase the therapeutic efficacy of ATR inhibitors. Additionally, this approach could help to activate innate immunity and increase T-cell immune infiltration in tumors, providing a rationale for a combination with immune checkpoint inhibitors.

cancer biology↗