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1. Spatiotemporal fractionation schemes for stereotactic radiosurgery of multiple brain metastases

   https://doi.org/10.1002/mp.16457  

   Torelli, Nathan; Papp, Dávid; Unkelbach, Jan (June 2023, Medical Physics)

   Abstract BackgroundStereotactic radiosurgery (SRS) is an established treatment for patients with brain metastases (BMs). However, damage to the healthy brain may limit the tumor dose for patients with multiple lesions. PurposeIn this study, we investigate the potential of spatiotemporal fractionation schemes to reduce the biological dose received by the healthy brain in SRS of multiple BMs, and also demonstrate a novel concept of spatiotemporal fractionation for polymetastatic cancer patients that faces less hurdles for clinical implementation. MethodsSpatiotemporal fractionation (STF) schemes aim at partial hypofractionation in the metastases along with more uniform fractionation in the healthy brain. This is achieved by delivering distinct dose distributions in different fractions, which are designed based on their cumulative biologically effective dose () such that each fraction contributes with high doses to complementary parts of the target volume, while similar dose baths are delivered to the normal tissue. For patients with multiple brain metastases, a novel constrained approach to spatiotemporal fractionation (cSTF) is proposed, which is more robust against setup and biological uncertainties. The approach aims at irradiating entire metastases with possibly different doses, but spatially similar dose distributions in every fraction, where the optimal dose contribution of every fraction to each metastasis is determined using a new planning objective to be added to the BED‐based treatment plan optimization problem. The benefits of spatiotemporal fractionation schemes are evaluated for three patients, each with >25 BMs. ResultsFor the same tumor BED₁₀and the same brain volume exposed to high doses in all plans, the mean brain BED₂can be reduced compared to uniformly fractionated plans by 9%–12% with the cSTF plans and by 13%–19% with the STF plans. In contrast to the STF plans, the cSTF plans avoid partial irradiation of the individual metastases and are less sensitive to misalignments of the fractional dose distributions when setup errors occur. ConclusionSpatiotemporal fractionation schemes represent an approach to lower the biological dose to the healthy brain in SRS‐based treatments of multiple BMs. Although cSTF cannot achieve the full BED reduction of STF, it improves on uniform fractionation and is more robust against both setup errors and biological uncertainties related to partial tumor irradiation. 

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2. Are we there yet? A machine learning architecture to predict organotropic metastases

   https://doi.org/10.1186/s12920-021-01122-7  

   Skaro, Michael; Hill, Marcus; Zhou, Yi; Quinn, Shannon; Davis, Melissa B.; Sboner, Andrea; Murph, Mandi; Arnold, Jonathan (December 2021, BMC Medical Genomics)

   Abstract Background & Aims Cancer metastasis into distant organs is an evolutionarily selective process. A better understanding of the driving forces endowing proliferative plasticity of tumor seeds in distant soils is required to develop and adapt better treatment systems for this lethal stage of the disease. To this end, we aimed to utilize transcript expression profiling features to predict the site-specific metastases of primary tumors and second, to identify the determinants of tissue specific progression. Methods We used statistical machine learning for transcript feature selection to optimize classification and built tree-based classifiers to predict tissue specific sites of metastatic progression. Results We developed a novel machine learning architecture that analyzes 33 types of RNA transcriptome profiles from The Cancer Genome Atlas (TCGA) database. Our classifier identifies the tumor type, derives synthetic instances of primary tumors metastasizing to distant organs and classifies the site-specific metastases in 16 types of cancers metastasizing to 12 locations. Conclusions We have demonstrated that site specific metastatic progression is predictable using transcriptomic profiling data from primary tumors and that the overrepresented biological processes in tumors metastasizing to congruent distant loci are highly overlapping. These results indicate site-specific progression was organotropic and core features of biological signaling pathways are identifiable that may describe proliferative plasticity in distant soils. 

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3. Beyond Antiresorptive Activity: Risedronate-Based Coordination Complexes To Potentially Treat Osteolytic Metastases

   https://doi.org/10.1021/acsabm.2c00648  

   Vélez, Gabriel Quiñones; Carmona-Sarabia, Lesly; Santiago, Alexandra París; Figueroa Guzmán, Angélica F.; Hu, Chunhua; Peterson-Peguero, Esther; López-Mejías, Vilmalí (January 2023, ACS Applied Bio Materials)

   Coordination of clinically employed bisphosphonate, risedronate (RISE), to bioactive metals, Ca2+, Mg2+, and Zn2+, allowed the formation of bisphosphonate-based coordination complexes (BPCCs). Three RISE-based BPCCs, RISE-Ca, RISEMg, and RISE-Zn, were produced, and their structures were elucidated by single crystal X-ray difraction. Interestingly, the addition of an auxiliary ligand, etidronic acid (HEDP), resulted in the recrystallized protonated form of the ligand, H-RISE. The pH-dependent structural stability of the RISE-based BPCCs was measured by means of dissolution profles under neutral and acidic simulated physiological conditions (PBS and FaSSGF, respectively). In comparison to RISE (Actonel), the complexes showed a lower equilibrium solubility (∼70−85% in 18−24 h) in PBS, while a higher equilibrium solubility (∼100% in 3 h) in acidic media. The results point to the capacity to release this BP in a pH-dependent manner from the RISE-based BPCCs. Subsequently, the particle size of RISE-Ca was reduced, from 300 μm to ∼350 d.nm, employing the phase inversion temperature (PIT)-nanoemulsion method, resulting in nano-Ca@RISE. Aggregation measurements of nano-Ca@RISE in 1% fetal bovine serum (FBS):H2O was monitored after 24, 48, and 72 h to study the particle size longevity in physiological media, showing that the suspended material has the potential to maintain its particle size over time. Furthermore, binding assays were performed to determine the potential binding of nano-Ca@RISE to the bone, where results show higher binding (~1.7×) for the material to hydroxyapatite (HA, 30%) when compared to RISE (17%) in 1 d. The cytotoxicity efects of nano-Ca@RISE were compared to those of RISE against the human breast cancer MDA-MB-231 and normal osteoblast-like hFOB 1.19 cell lines by dose−response curves and relative cell viability assays in an in vitro setting. The results demonstrate that nano-Ca@RISE signifcantly decreases the viability of MDA-MB-231 with high specifcity, at concentrations ∼2−3× lower than the ones reported employing other third-generation BPs. This is supported by the fact that when normal osteoblast cells (hFOB 1.19), which are part of the tissue microenvironment at metastatic sites, were treated with nano-Ca@RISE no signifcant decrease in viability was observed. This study expands on the therapeutic potential of RISE beyond its antiresorptive activity through the design of BPCCs, specifcally nano-Ca@RISE, that bind to the bone and degrade in a pH-dependent manner under acidic conditions 

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4. The blood–brain barrier and blood–tumour barrier in brain tumours and metastases

   https://doi.org/10.1038/s41568-019-0205-x  

   Arvanitis, Costas D.; Ferraro, Gino B.; Jain, Rakesh K. (January 2020, Nature Reviews Cancer)

   null (Ed.)
5. Intracellular delivery of protein drugs with an autonomously lysing bacterial system reduces tumor growth and metastases

   https://doi.org/10.1038/s41467-021-26367-9  

   Raman, Vishnu; Van Dessel, Nele; Hall, Christopher L.; Wetherby, Victoria E.; Whitney, Samantha A.; Kolewe, Emily L.; Bloom, Shoshana M. K.; Sharma, Abhinav; Hardy, Jeanne A.; Bollen, Mathieu; et al (October 2021, Nature Communications)

   Abstract Critical cancer pathways often cannot be targeted because of limited efficiency crossing cell membranes. Here we report the development of a Salmonella-based intracellular delivery system to address this challenge. We engineer genetic circuits that (1) activate the regulatorflhDCto drive invasion and (2) induce lysis to release proteins into tumor cells. Released protein drugs diffuse from Salmonella containing vacuoles into the cellular cytoplasm where they interact with their therapeutic targets. Control of invasion withflhDCincreases delivery over 500 times. The autonomous triggering of lysis after invasion makes the platform self-limiting and prevents drug release in healthy organs. Bacterial delivery of constitutively active caspase-3 blocks the growth of hepatocellular carcinoma and lung metastases, and increases survival in mice. This success in targeted killing of cancer cells provides critical evidence that this approach will be applicable to a wide range of protein drugs for the treatment of solid tumors. 

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