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Treatment paradigms for patients with upper tract urothelial carcinoma (UTUC) are typically extrapolated from studies of bladder cancer despite their distinct clinical and molecular characteristics. The advancement of UTUC research is hampered by the lack of diseasespecific models. Here, we report the establishment of patient derived xenograft (PDX) and cell line models that reflect the genomic and biological heterogeneity of the human disease. Models demonstrate high genomic concordance with the corresponding patient tumors, with invasive tumors more likely to successfully engraft. Treatment of PDX models with chemotherapy recapitulates responses observed in patients. Analysis of a HER2 S310F-mutant PDX suggests that an antibody drug conjugate targeting HER2 would have superior efficacy versus selective HER2 kinase inhibitors. In sum, the biological and phenotypic concordance between patient and PDXs suggest that these models could facilitate studies of intrinsic and acquired resistance and the development of personalized medicine strategies for UTUC patients.

Our increasing knowledge of the mechanisms behind the progression of pancreatic cancer (PC) has not yet translated into effective treatments. Many promising drugs have failed in the clinic, highlighting the need for better preclinical models to assess drug efficacy and characterize mechanisms of resistance. Using different experimental models, including patient-derived xenografts (PDXs), we gauged the efficacy of therapies aimed at two hallmark lesions of PCs: activation of signaling pathways by oncogenic KRAS and inactivation of tumor-suppressor genes. Although the drug targeting inactivation of tumor suppressors by DNA methylation had little effect, the inhibition of Mek, a K-Ras effector, in combination with the standard of care (chemotherapy consisting of gemcitabine/Nab-paclitaxel), reduced the growth of three out of five PC-PDXs and impaired metastasis. The two least responding PC-PDXs were composed of genetically diverse cells, which displayed sensitivities to the Mek inhibitor differing by >10-fold. Unexpectedly, our analysis of this genetic diversity unveiled different KRAS mutations. As mutation in KRAS occurs early during progression, this heterogeneity may reflect the simultaneous appearance of different malignant cellular clones or, alternatively, that cells containing two mutations of KRAS are selected during tumor evolution. In vitro and in vivo analyses indicated that the intratumoral heterogeneity, along with the selective pressure imposed by the Mek inhibitor, resulted in rapid selection of resistant cells. Together with the gemcitabine/Nab-paclitaxel backbone, Mek inhibition could be effective in treatment of PC. However, resistance because of intratumoral heterogeneity is likely to develop frequently, pointing to the necessity of identifying the factors and mechanisms of resistance to further develop this therapy.

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The development of therapeutic matrix metalloproteinase (MMP) inhibitors has evolved from broad-spectrum peptidomimetic inhibitors with deleterious side effects, to highly selective agents. These range from small molecules to antibodies, antisense inhibitors, and engineered N-terminal tissue inhibitors of metalloproteinase domain. The advances in inhibitor design along with promising new global molecular insights into MMP structures, the protease web, and the role of extracellular matrix in diseases have contributed toward a renewed interest in using MMPs as valid drug targets. This review aims to address the advances and challenges concerning the design, development, and current status of anti-MMP agents in this new era of post-broad-spectrum MMP inhibitors. Highly selective inhibitors of MMPs promise to usher in an era of specific targeting of diseased tissue proteolysis networks, with markedly reduced negative repercussions, and to uncover the molecular and mechanistic roles of MMP isoforms in cancer, inflammation, and infection.