Recognition of G-quadruplex topology through hybrid binding with implications in cancer theranostics

Abstract

The selective recognition and imaging of oncogene specific G-quadruplex (GQ) structures holds great promise in the development of diagnostic therapy (theranostics) for cancer and has been challenging due to their structural dynamics and diversity. We report selective recognition of GQ by a small molecule through unique hybrid loop stacking and groove binding mode with turn on far-red fluorescence response and anticancer activity demonstrating the potential implications for GQ-targeted cancer theranostics. Methods: Biophysical investigation reveal the turn on far-red emission property of TGP18 for selective recognition of GQ. In cellulo studies including DNA damage and oxidative stress evaluation guided us to perform in vitro (3D spheroid) and in vivo (xenograft mice model) anti-cancer activity, and tumor tissue imaging to assess the theranostic potential of TGP18. Results: Neocuproine-based far-red turn on fluorescence probe TGP18 shows GQ-to-duplex selectivity and specifically recognizes BCL-2 GQ with high affinity through a unique hybrid binding mode involving loop-stacking and groove interactions. Our study reveals that the selective recognition originating from the distinct loop structure of GQ that alters the overall probe interaction and binding affinity. TGP18 binding to anti-apoptotic BCL-2 GQ ablates the pro-survival function and elicit anti-cancer activity by inducing apoptosis in cancer cells. We deciphered that inhibition of BCL-2 transcription synergized with signaling cascade of nucleolar stress, DNA damage and oxidative stress in triggering apoptosis signaling pathway. Conclusion: Intervention of GQ mediated lethality by TGP18 has translated into anti-cancer activity in both in vitro 3D spheroid culture and in vivo xenograft models of lung and breast cancer with superior efficacy for the former. In vivo therapeutic efficacy supplemented with tumor 3D spheroid and tissue imaging potential define the role of TGP18 in GQ-targeted cancer theranostics.

Dendrimer Architectonics to Treat Cancer and Neurodegenerative Diseases with Implications in Theranostics and Personalized Medicine

“…In practice, fluorescent probes are conjugated or entrapped in DA along with a therapeutic drug to render them the theranostic capability. Notably, some probes are inherently theranostic in nature with both therapeutic and imaging capabilities. − …”

“…Oncogene specific G-quadruplex (GQ) structure holds a great promise in cancer theranostics. We developed a neocuproine-based far-red turn-on fluorescence probe (TGP18) with topology selectivity and specificity to recognize BCL-2 GQ . The topology selective binding of BCL-2 Q by TGP18 was attributed to unique hybrid binding mode involving loop-stacking and groove interactions.…”

“…We developed a neocuproine-based far-red turnon fluorescence probe (TGP18) with topology selectivity and specificity to recognize BCL-2 GQ. 107 The topology selective binding of BCL-2 Q by TGP18 was attributed to unique hybrid binding mode involving loop-stacking and groove interactions. Anticancer activity in both in vitro 3D spheroid culture and in vivo xenograft models of lung and breast cancer have shown superior efficacy of TGP18 for the former.…”

Targeting Oncogene Promoters and Ribosomal RNA Biogenesis by G-Quadruplex Binding Ligands Translate to Anticancer Activity

“…However, the dynamic relationships between GQ formation and cellular functions are poorly understood. , The common cross-linking and fixation methods change the cytoplasmic density, resulting in a damaged organelle and the extraction of nuclear proteins, which perturb real-time monitoring of GQ dynamics. , Moreover, antibody-based GQ staining allows only high GQ density domains to form fluorescent foci while the detection of the low GQ density domains is limited by spatial resolution . In this context, cell membrane-permeable small molecule fluorescent probes that specifically recognize cellular GQs circumvent the limitations of fixed cell artefacts and offer powerful and direct means of probing their dynamic folding and subcellular localization in live cells. ,, In recent times, various fluorescent probes are developed to detect cytoplasmic RNA , and DNA GQs in subcellular organelles of live cells, − but, their applications are limited by the off-target effects, raising an unmet need for the development of GQ-specific fluorescent probes that offer dynamic monitoring of GQ targets in live cells with reduced off-target effects.…”

Ratiometric Fluorescence Imaging for the Distribution of Nucleic Acid Content in Living Cells and Human Tissue Sections

“…D­(donor)−π–A­(acceptor)-type dyes could present excellent fluorescence response to nucleic acids because of their rotational reduction and hydrophobic interaction after binding with nucleic acids. − Herein, we rationally designed three novel D−π–A−π–D-type probes ( QMP-AS , QPP-AS , and QPP-PS ) for ratiometric fluorescence response of nucleic acids. The crescent-shape structure and positive charge of the probes were designed to improve the interaction between nucleic acids and probes.…”