Aurora Kinases as Therapeutic Targets in Head and Neck Cancer.

ABSTRACT: The Aurora kinases (AURKA and AURKB) have attracted attention as therapeutic targets in head and neck squamous cell carcinomas. Aurora kinases were first defined as regulators of mitosis that localization to the centrosome (AURKA) and centromere (AURKB), governing formation of the mitotic spindle, chromatin condensation, activation of the core mitotic kinase CDK1, alignment of chromosomes at metaphase, and other processes. Subsequently, additional roles for Aurora kinases have been defined in other phases of cell cycle, including regulation of ciliary disassembly and DNA replication. In cancer, elevated expression and activity of Aurora kinases result in enhanced or neomorphic locations and functions that promote aggressive disease, including promotion of MYC expression, oncogenic signaling, stem cell identity, epithelial-mesenchymal transition, and drug resistance. Numerous Aurora-targeted inhibitors have been developed and are being assessed in preclinical and clinical trials, with the goal of improving head and neck squamous cell carcinoma treatment.

Association of TP53 and CDKN2A Mutation Profile with Tumor Mutation Burden in Head and Neck Cancer.

PURPOSE: Head and neck squamous cell carcinoma (HNSCC) is a frequently devastating cancer that affects more than a half million people annually worldwide. Although some cases arise from infection with human papillomavirus (HPV), HPV-negative HNSCC is more common, and associated with worse outcome. Advanced HPV-negative HNSCC may be treated with surgery, chemoradiation, targeted therapy, or immune checkpoint inhibition (ICI). There is considerable need for predictive biomarkers for these treatments. Defects in DNA repair capacity and loss of cell-cycle checkpoints sensitize tumors to cytotoxic therapies, and can contribute to phenotypes such as elevated tumor mutation burden (TMB), associated with response to ICI. Mutation of the tumor suppressors and checkpoint mediators TP53 and CDKN2A is common in HPV-negative HNSCC. EXPERIMENTAL DESIGN: To gain insight into the relation of the interaction of TP53 and CDKN2A mutations with TMB in HNSCC, we have analyzed genomic data from 1,669 HPV-negative HNSCC tumors with multiple criteria proposed for assessing the damaging effect of TP53 mutations. RESULTS: Data analysis established the TP53 and CDKN2A mutation profiles in specific anatomic subsites and suggested that specific categories of TP53 mutations are more likely to associate with CDKN2A mutation or high TMB based on tumor subsite. Intriguingly, the pattern of hotspot mutations in TP53 differed depending on the presence or absence of a cooccurring CDKN2A mutation. CONCLUSIONS: These data emphasize the role of tumor subsite in evaluation of mutational profiles in HNSCC, and link defects in TP53 and CDKN2A to elevated TMB levels in some tumor subgroups.

Ultrasound-Guided Cytosolic Protein Delivery via Transient Fluorous Masks.

The inability to spatiotemporally guide proteins in tissues and efficiently deliver them into cells remains a key barrier to realizing their full potential in precision medicine. Here, we report ultrasound-sensitive fluoro-protein nanoemulsions which can be acoustically tracked, guided, and activated for on-demand cytosolic delivery of proteins, including antibodies, using clinically relevant diagnostic ultrasound. This advance is accessed through the discovery of a family of fluorous tags, or FTags, that transiently mask proteins to mediate their efficient dispersion into ultrasound-sensitive liquid perfluorocarbons, a phenomenon akin to dissolving an egg in liquid Teflon. We identify the biochemical basis for protein fluorous masking and confirm FTag coatings are shed during delivery, without disrupting the protein structure or function. Harnessing the ultrasound sensitivity of fluorous emulsions, real-time imaging is used to simultaneously monitor and activate FTag-protein complexes to enable controlled cytosolic antibody delivery in vitro and in vivo. These findings may advance the development of image-guided, protein-based biosensing and therapeutic modalities.

Experimental validation of magnetically focused proton beams for radiosurgery.

We performed experiments using a triplet of quadrupole permanent magnets to focus protons and compared their dose distributions with unfocused collimated beams using energies and field sizes typically employed in proton radiosurgery. Experiments were performed in a clinical treatment room wherein small-diameter proton beams were focused by a magnet triplet placed immediately upstream of a water tank. The magnets consisted of segments of Sm2Co17 rare-earth permanent magnetic material adhered into Halbach cylinders with nominal field gradients of 100, 150, 200, and 250 T m-1. Unmodulated beams with initial diameters of 3 mm-20 mm were delivered using a single scattering system with nominal energies of 127 and 157 MeV (respective ranges of ~10 cm and 15 cm in water), commonly used for proton radiosurgery at our institution. For comparison, small-diameter unfocused collimated beams were similarly delivered. Transverse and depth dose distributions were measured using radiochromic film and a diode detector, respectively, and compared between the focused and unfocused beams (UNF). The focused beams produced low-eccentricity beam spots (defined by the 80% dose contour) at Bragg depth, with full width at 80% maximum dose values ranging from 3.8 to 7.6 mm. When initial focused beam diameters were larger than matching unfocused diameters (19 of 29 cases), the focused beams peak-to-entrance dose ratios were 13% to 73% larger than UNF. In addition, in 17 of these cases the efficiency of dose delivery to the target was 1.3× to 3.3× larger. Both peak-to-entrance dose ratios and efficiency tended to increase with initial beam diameter, while efficiency also tended to increase with magnet gradient. These experimental results are consistent with our previous Monte Carlo (MC) studies and suggest that a triplet of quadrupole Halbach cylinders could be clinically useful for irradiating small-field radiosurgical targets with fewer beams, lower entrance dose, and shorter treatment times.

Monte Carlo evaluation of magnetically focused proton beams for radiosurgery.

The purpose of this project is to investigate the advantages in dose distribution and delivery of proton beams focused by a triplet of quadrupole magnets in the context of potential radiosurgery treatments. Monte Carlo simulations were performed using various configurations of three quadrupole magnets located immediately upstream of a water phantom. Magnet parameters were selected to match what can be commercially manufactured as assemblies of rare-earth permanent magnetic materials. Focused unmodulated proton beams with a range of ~10 cm in water were target matched with passive collimated beams (the current beam delivery method for proton radiosurgery) and properties of transverse dose, depth dose and volumetric dose distributions were compared. Magnetically focused beams delivered beam spots of low eccentricity to Bragg peak depth with full widths at the 90% reference dose contour from ~2.5 to 5 mm. When focused initial beam diameters were larger than matching unfocused beams (10 of 11 cases) the focused beams showed 16%-83% larger peak-to-entrance dose ratios and 1.3 to 3.4-fold increases in dose delivery efficiency. Peak-to-entrance and efficiency benefits tended to increase with larger magnet gradients and larger initial diameter focused beams. Finally, it was observed that focusing tended to shift dose in the water phantom volume from the 80%-20% dose range to below 20% of reference dose, compared to unfocused beams. We conclude that focusing proton beams immediately upstream from tissue entry using permanent magnet assemblies can produce beams with larger peak-to-entrance dose ratios and increased dose delivery efficiencies. Such beams could potentially be used in the clinic to irradiate small-field radiosurgical targets with fewer beams, lower entrance dose and shorter treatment times.