Most solid tumors are comprised of multiple clones that express orthogonal antigens, suggesting that novel strategies must be developed in order to adapt chimeric antigen receptor (CAR) T-cell therapies to treat heterogeneous solid tumors.

Complete surgical resection of malignant disease is the only reliable method to cure cancer. Unfortunately, quantitative tumor resection is often limited by a surgeon's ability to locate all malignant disease and distinguish it from healthy tissue. Fluorescence-guided surgery has emerged as a tool to aid surgeons in the identification and removal of malignant lesions. While nontargeted fluorescent dyes have been shown to passively accumulate in some tumors, the resulting tumor-to-background ratios are often poor, and the boundaries between malignant and healthy tissues can be difficult to define. To circumvent these problems, our laboratory has developed high affinity tumor targeting ligands that bind to receptors that are overexpressed on cancer cells and deliver attached molecules selectively into these cells. In this study, we explore the use of two tumor-specific targeting ligands (i.e., folic acid that targets the folate receptor (FR) and DUPA that targets prostate specific membrane antigen (PSMA)) to deliver near-infrared (NIR) fluorescent dyes specifically to FR and PSMA expressing cancers, thereby rendering only the malignant cells highly fluorescent. We report here that all FR- and PSMA-targeted NIR probes examined bind cultured cancer cells in the low nanomolar range. Moreover, upon intravenous injection into tumor-bearing mice with metastatic disease, these same ligand-NIR dye conjugates render receptor-expressing tumor tissues fluorescent, enabling their facile resection with minimal contamination from healthy tissues.

Photodynamic therapy (PDT) involves use of a photosensitizer, whose activation with light leads to the production of singlet oxygen (SOS), generation of reactive oxygen species (ROS), and initiation of associated cell toxicity. Because a cell’s mitochondria constitute sites where oxygen levels are high, ROS can be readily produced, and apoptosis is commonly initiated. Therefore, an ideal PDT agent might be a potent photosensitizer that could naturally accumulate in mitochondria. Although a number of mitochondria-targeting moieties, including triphenylphosphine, guanidinium, and bisguanidium, have been identified, a quantitative comparison of their efficacies in targeting mitochondria has not been performed. In this study, we have prepared triphenylphosphine, guanidinium, and bisguanidium derivatives of the FDA-approved PDT agent verteporfin (Visudyne, benzoporphyrin derivative-monoacid ring A: BPD-MA) and compared their abilities to induce the intracellular perturbations common to potent PDT agents. Cellular parameters examined included subcellular localization of the verteporfin, real-time monitoring of SOS production, quantitation of reactive oxygen species (ROS) generation, analysis of mitochondria and chromatin integrity, characterization of cytoskeletal disruption and evaluation of cytochrome C release as a measure of apoptosis. An analysis of these parameters demonstrates that the triphenylphosphine derivative (0323) has better mitochondria-targeting efficacy, SOS production, and mitochondria membrane toxicity than either unmodified verteporfin or its guanidinium derivatives. Consistent with this potency, 0323 also induced the most prominent mitochondria swelling, actin depolymerization, pyknosis, and cytochrome C release. We conclude that triphenylphosphine has a better mitochondria-targeting moiety than guanidinium or bis-guanidinium and those PDT photosensitizers with improved cytotoxicities can be prepared by conjugating a mitochondria-targeting moiety to the desired photosensitizer.

Because the most reliable therapy for cancer involves quantitative resection of all diseased tissue, considerable effort has been devoted to improving a surgeon's ability to locate and remove all malignant lesions. With the aid of improved optical imaging equipment, we and others have focused on developing tumor-targeted fluorescent dyes to selectively illuminate cancer nodules during surgery. We describe here the design, synthesis, optical properties, in vitro and in vivo tumor specificity/ affinity, pharmacokinetics, preclinical toxicology, and some clinical application of a folate receptor (FR)-targeted NIR dye (OTL38) that concentrates specifically in cancer tissues and clears rapidly from healthy tissues. We demonstrate that OTL38 binds FR-expressing cells with ∼1 nM affinity and eliminates from receptor negative tissues with a half-time of <30 min. We further show that OTL38 enables visualization of malignant lesions at concentrations less than 100-fold those required to elicit signs of toxicity. Since OTL38 also provides excellent tumor contrast in both murine tumor models and human cancer patients, we conclude that OTL38 constitutes an excellent NIR dye for fluorescence-guided resection of malignant lesions in cancer patients.

Class III β-tubulin plays a prominent role in the development of drug resistance to paclitaxel by allowing the incorporation of the GBP1 GTPase into microtubules. Once in the cytoskeleton, GBP1 binds to prosurvival kinases such as PIM1 and initiates a signaling pathway that induces resistance to paclitaxel. Therefore, the inhibition of the GBP1:PIM1 interaction could potentially revert resistance to paclitaxel. A panel of 44 4-azapodophyllotoxin derivatives was screened in the NCI-60 cell panel. The result is that 31 are active and the comparative analysis demonstrated specific activity in paclitaxel-resistant cells. Using surface plasmon resonance, we were able to prove that NSC756093 is a potent in vitro inhibitor of the GBP1:PIM1 interaction and that this property is maintained in vivo in ovarian cancer cells resistant to paclitaxel. Through bioinformatics, molecular modeling, and mutagenesis studies, we identified the putative NSC756093 binding site at the interface between the helical and the LG domain of GBP1. According to our results by binding to this site, the NSC756093 compound is able to stabilize a conformation of GBP1 not suitable for binding to PIM1.

Tumor-targeted near-infrared fluorescent dyes have the potential to improve cancer surgery by enabling surgeons to locate and resect more malignant lesions where good visualization tools are required to ensure complete removal of malignant tissue. Although the tumor-targeted fluorescent dyes used in humans to date have been either small organic molecules or high molecular weight antibodies, low molecular weight protein scaffolds have attracted significant attention because they penetrate solid tumors almost as efficiently as small molecules, but can be infinitely mutated to bind almost any antigen. Here we describe the use of a 10 kDa protein scaffold, a Centyrin, to target a near-infrared fluorescent dye to tumors that overexpress the epidermal growth factor receptor (EGFR) for fluorescence-guided surgery (FGS). We have developed and optimized the dose and time required for imaging small tumor burdens with minimal background fluorescence in real-time fluorescence-guided surgery of EGFR-expressing tumor xenografts in murine models. We demonstrate that the Centyrin-near-infrared dye conjugate (CNDC) binds selectively to human EGFR cancer cells with an EC of 2 nM, localizes to EGFR tumor xenografts in athymic nude mice and that uptake of the dye in xenografts is significantly reduced when EGFR are blocked by preinjection of excess unlabeled Centyrin. Taken together, these data suggest that CNDCs can be used for intraoperative identification and surgical removal of EGFR-expressing lesions and that Centyrins targeted to other tumor-specific antigens should prove similarly useful in fluorescence guided surgery of cancer. In addition, we demonstrate that the CNDC is detected in the NIR region of the spectrum and can be utilized for fluorescence-guided surgery (FGS). In addition, we propose that with its eventual complete clearance from EGFR-negative tissues and its quantitative retention in the tumor mass for >24 h, a Centyrin-targeted NIR dye should provide excellent tumor contrast when injected at least 6-8 h before initiation of cancer surgery in human patients.

Ureters can be accidentally severed during pelvic surgeries, significantly prolonging the times in the operating room to allow for complete repair of damaged ureters and leading to significant morbidities associated with consequent ureter obstruction and possible kidney dysfunction. In an effort to prevent these complications, light-emitting stents and urine-excreted dyes have been introduced to illuminate the ureter during surgery. However, problems with mechanical insertion, ureter spasm, image contrast, and localized injection have limited interest in their clinical applications. We report here the synthesis and characterization of a new near-infrared (NIR) fluorescent dye (UreterGlow) that can be injected systemically but is excreted primarily through the renal system, allowing ureter imaging with an NIR fluorescence camera. Following intravenous injection of 0.1 mg/kg UreterGlow, we have monitored the flow of UreterGlow through the proximal, medial, and distal segments of the ureter. The timing of ureter visualization was calculated from the time of injection of the drug. The null hypothesis was that "Visualization of the ureter in pigs is possible 60 min after administration of UreterGlow using an NIR camera". UreterGlow displayed excitation and emission maxima of λ = 800 nm and λ = 830 nm in phosphate buffered saline, pH 7.4, and could be imaged in the urinary tract in mice. Shortly after injection of UreterGlow into Yorkshire pigs, peristalsis of the ureter could be observed. The distal ureter could be visualized under NIR illumination after 60 min with constant fluorescence in all five pigs for >2 h. The same ureters could not be seen using visible light ( X, p = 0.0001). Because both excitation and emission of UreterGlow occurs at >30 nm longer wavelength than most tumor-imaging fluorescent dyes, it should be possible to distinguish ureter fluorescence from tumor fluorescence with this dye.

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