Imaging cellular distribution of Bcl inhibitors using small molecule drug conjugates

Mitochondria of T Lymphocytes Promote Anti-Pulmonary Tumor Immune Response

Background

B-cell lymphoma 2 (Bcl-2), a protein involved in apoptosis, has been proven to have carcinogenic potential and is well documented. With the recent advancement in optical technology, it has become possible to observe subcellular organelles such as mitochondria in real-time without the need for staining. Consequently, we have examined the movement of mitochondria in cancer cells, correlating it with the regulation of Bcl-2.

Methods

Using a tomographic microscope, which can detect the internal structure of cells, we observed lung tumor cells. Cells were exposed to a laser beam (λ = 520 nm) inclined at 45°, and holographic images were recorded up to a depth of 30 µm of reconstruction.

Results

Intriguingly, lung tumor cells rapidly expelled mitochondria upon the attachment of Bcl-2 or B-cell lymphoma extra-large (Bcl-xL) inhibitors. On the other hand, we observed that tumor cells hijack mitochondria from T cells. The hijacked mitochondria were not immediately linked to tumor cell death, but they played a role in assisting granzyme B-induced tumor cell death. Due to lower levels of Bcl-2 and Bcl-xL on the mitochondria of T cells compared to lung tumor cells, immune cells depleted of Bcl-2 and Bcl-xL were co-cultured with the tumor cells.

Conclusions

As a result, a more effective tumor cell death induced by granzyme B was observed. Additionally, further enhanced anticancer immune response was observed in vivo. Together, we show that modified mitochondria of T cells can provide potential novel strategies towards tumor cell death.

SMALL MOLECULE IMAGING AGENT FOR MUTANT KRAS G12C

Multiple potent covalent inhibitors for mutant KRAS G12C have been described and some are in clinical trials. These small molecule inhibitors potentially allow for companion imaging probe development, thereby expanding the chemical biology toolkit to investigate mutant KRAS biology. Herein, we synthesized and tested a series of fluorescent companion imaging drugs (CID) for KRAS G12C, using two scaffolds, ARS-1323 and AMG-510. We created four fluorescent derivatives of each by attaching BODIPY dyes. We found that two fluorescent derivatives (BODIPY FL and BODIPY TMR) of ARS-1323 bind mutant KRAS and can be used for biochemical binding screens. Unfortunately, these drugs could not be used as direct imaging agents in cells, likely because of non-specific membrane labeling. To circumvent this challenge, we then used a two step procedure in cancer cells where an ARS-1323 alkyne is used for target binding followed by fluorescence imaging after in situ click chemsitry with picolyl azide Alexa Fluor 647. We show that this approach can be used to image mutant KRAS G12C directly in cells. Given the current lack of mutant KRAS G12C specific antibodies, these reagents could be useful for specific fluorescence imaging.

A "Three-in-One" Multifunctional Probe for Bcl-2/Mcl-1 Profiling and Visualizing in Situ

Bcl-2 and Mcl-1, the two arms of the anti-apoptotic Bcl-2 family proteins, have been identified as key regulators of apoptosis and effective therapeutic targets of cancer. However, no small-molecular probe is capable of profiling and visualizing both Bcl-2 and Mcl-1 simultaneously in situ. Herein, we report a multifunctional molecular probe (BnN₃ -OPD-Alk) by a "three-in-one" molecular designing strategy, which integrated the Bcl-2/Mcl-1 binding ligand, fluorescent reporter group and photoreactive group azido into the same scaffold. BnN₃ -OPD-Alk exhibited sub-micromolar affinities to Bcl-2/Mcl-1 and bright green self-fluorescence. It was then successfully applied for Bcl-2/Mcl-1 labeling, capturing, enriching, and bioimaging both in vitro and in cells. This strategy could facilitate the precise early diagnosis and effective therapy of dual Bcl-2/Mcl-1-related diseases.

Synergistic antitumor effects of 9.2.27-PE38KDEL and ABT-737 in primary and metastatic brain tumors

Standard treatment, unfortunately, yields a poor prognosis for patients with primary or metastatic cancers in the central nervous system, indicating a necessity for novel therapeutic agents. Immunotoxins (ITs) are a class of promising therapeutic candidates produced by fusing antibody fragments with toxin moieties. In this study, we investigated if inherent resistance to IT cytotoxicity can be overcome by rational combination with pro-apoptotic enhancers. Therefore, we combined ITs (9.2.27-PE38KDEL or Mel-14-PE38KDEL) targeting chondroitin sulfate proteoglycan 4 (CSPG4) with a panel of Bcl-2 family inhibitors (ABT-737, ABT-263, ABT-199 [Venetoclax], A-1155463, and S63845) against patient-derived glioblastoma, melanoma, and breast cancer cells/cell lines. In vitro cytotoxicity assays demonstrated that the addition of the ABT compounds, specifically ABT-737, sensitized the different tumors to IT treatment, and improved the IC₅₀ values of 9.2.27-PE38KDEL up to >1,000-fold. Mechanistic studies using 9.2.27-PE38KDEL and ABT-737 revealed that increased levels of intracellular IT, processed (active) exotoxin, and PARP cleavage correlated with the enhanced sensitivity to the combination treatment. Furthermore, we confirmed the synergistic effect of 9.2.27-PE38KDEL and ABT-737 combination therapy in orthotopic GBM xenograft and cerebral melanoma metastasis models in nude mice. Our study defines strategies for overcoming IT resistance and enhancing specific antitumor cytotoxicity in primary and metastatic brain tumors.

Synthesis and Antiviral Activity of Sulfonohydrazide and 1,3,4-Oxadiazole Derivatives of 6,6-Dimethyl-9-Oxo-4,5,6,7,8,9-Hexahydropyrazolo[5,1-b] Quinazoline

A series of new 6,6-dimethyl-9-oxo-4,5,6,7,8,9-hexahydropyrazolo[5,1-b]quinazoline substituted benzenesulfonohydrazide and 1,3,4-oxadiazole derivatives has been synthesised and characterised using spectral techniques. The antiviral activity of these compounds against an avian paramyxovirus (APMV-1) has been screened and the results show that some of the compounds possess good antiviral activity

Environment-Sensitive Fluorescent Probe for the Human Ether-a-go-go-Related Gene Potassium Channel

A novel environment-sensitive probe S2 with turn-on switch for Human Ether-a-go-go-Related Gene (hERG) potassium channel was developed herein. After careful evaluation, this fluorescent probe showed high binding affinity with hERG potassium channel with an IC₅₀ value of 41.65 nM and can be well applied to hERG channel imaging or cellular distribution study for hERG channel blockers. Compared with other imaging techniques, such as immunofluorescence and fluorescent protein-based approaches, this method is convenient and affordable, especially since a washing procedure is not needed. Meanwhile, this environment-sensitive turn-on design strategy may provide a good example for the probe development for these targets that have no reactive or catalytic activity.