Long-lived cancer stem cells (CSCs) with indefinite proliferative potential have been identified in multiple epithelial cancer types. These cells are likely derived from transformed adult stem cells and are thought to share many characteristics with their parental population, including a quiescent slow-cycling phenotype. Various label-retaining techniques have been used to identify normal slow cycling adult stem cell populations and offer a unique methodology to functionally identify and isolate cancer stem cells. The quiescent nature of CSCs represents an inherent mechanism that at least partially explains chemotherapy resistance and recurrence in posttherapy cancer patients. Isolating and understanding the cell cycle regulatory mechanisms of quiescent cancer cells will be a key component to creation of future therapies that better target CSCs and totally eradicate tumors. Here we review the evidence for quiescent CSC populations and explore potential cell cycle regulators that may serve as future targets for elimination of these cells.

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Large-scale genetic analyses of human tumor samples have been used to identify novel oncogenes, tumor suppressors and prognostic factors, but the functions and molecular interactions of many individual genes have not been determined. In this study we examined the cellular effects and molecular mechanism of the arrestin family member, ARRDC3, a gene preferentially lost in a subset of breast cancers. Oncomine data revealed that the expression of ARRDC3 decreases with tumor grade, metastases and recurrences. ARRDC3 overexpression represses cancer cell proliferation, migration, invasion, growth in soft agar and in vivo tumorigenicity, whereas downregulation of ARRCD3 has the opposite effects. Mechanistic studies showed that ARRDC3 functions in a novel regulatory pathway that controls the cell surface adhesion molecule, β-4 integrin (ITGβ4), a protein associated with aggressive tumor behavior. Our data indicates ARRDC3 directly binds to a phosphorylated form of ITGβ4 leading to its internalization, ubiquitination and ultimate degradation. The results identify the ARRCD3-ITGβ4 pathway as a new therapeutic target in breast cancer and show the importance of connecting genetic arrays with mechanistic studies in the search for new treatments.

Recapitulation of the tumor microenvironment is critical for probing mechanisms involved in cancer, and for evaluating the tumor-killing potential of chemotherapeutic agents, targeted therapies and immunotherapies. Microfluidic devices have emerged as valuable tools for both mechanistic studies and for preclinical evaluation of therapeutic agents, due to their ability to precisely control drug concentrations and gradients of oxygen and other species in a scalable and potentially high throughput manner. Most existing in vitro microfluidic cancer models are comprised of cultured cancer cells embedded in a physiologically relevant matrix, collocated with vascular-like structures. However, the recent emergence of immune checkpoint inhibitors (ICI) as a powerful therapeutic modality against many cancers has created a need for preclinical in vitro models that accommodate interactions between tumors and immune cells, particularly for assessment of unprocessed tumor fragments harvested directly from patient biopsies. Here we report on a microfluidic model, termed EVIDENT (ex vivo immuno-oncology dynamic environment for tumor biopsies), that accommodates up to 12 separate tumor biopsy fragments interacting with flowing tumor-infiltrating lymphocytes (TILs) in a dynamic microenvironment. Flow control is achieved with a single pump in a simple and scalable configuration, and the entire system is constructed using low-sorption materials, addressing two principal concerns with existing microfluidic cancer models. The system sustains tumor fragments for multiple days, and permits real-time, high-resolution imaging of the interaction between autologous TILs and tumor fragments, enabling mapping of TIL-mediated tumor killing and testing of various ICI treatments versus tumor response. Custom image analytic algorithms based on machine learning reported here provide automated and quantitative assessment of experimental results. Initial studies indicate that the system is capable of quantifying temporal levels of TIL infiltration and tumor death, and that the EVIDENT model mimics the known in vivo tumor response to anti-PD-1 ICI treatment of flowing TILs relative to isotype control treatments for syngeneic mouse MC38 tumors.

Purpose: To date, there has not been a large, systematic evaluation of the prevalence of germline risk variants in urothelial carcinoma (UC). Methods:We evaluated the frequency of germline pathogenic and likely pathogenic variants in 1038 patients with high-risk UC who underwent targeted clinical germline testing. Case-control enrichment analysis was performed to screen for pathogenic variant enrichment in 17 DNA repair genes in 1038 UC patients relative to cancer-free individuals.Results: Among 1038 patients with UC, the cumulative frequency of patients with pathogenic variants was 24%; 18.6% of patients harbored ≥1 actionable germline variant with preventive or therapeutic utility. MSH2 (34/969, 3.5%) and BRCA1/2 (38/867, 4.4%) germline variants had the highest frequency. Germline variants in DNA damage repair genes accounted for 78% of pathogenic germline variants. Compared to the cancer-free cohort, UC patients had significant variant enrichment in MSH2 (odds ratio [OR]: 15.4, 95% confidence interval [CI]: 7.1-32.7, p < 0.0001), MLH1 (OR: 15.9, 95% CI: 4.4-67.7, p < 0.0001), BRCA2 (OR: 5.7, 95% CI: 3.2-9.6, p < 0.0001), and ATM (OR: 3.8, 95% CI: 1.8-8.3, p = 0.02). Conclusion:In this study, 24% of UC patients harbored pathogenic germline variants and 18.6% had clinically actionable variants. MLH1 and MSH2 were validated as UC risk genes while ATM and BRCA2 were highlighted as potential UC predisposition genes. This work emphasizes the utility of germline testing in selected high-risk UC cohorts. (2020) 22:709-718; https://doi. Genetics in Medicine

Mutations in the ALK tyrosine kinase receptor gene represent important therapeutic targets in neuroblastoma, yet their clinical translation has been challenging. The ALKF1174L mutation is sensitive to the ALK inhibitor crizotinib only at high doses and mediates acquired resistance to crizotinib in ALK-translocated cancers. We have shown that the combination of crizotinib and an inhibitor of downstream signaling induces a favorable response in transgenic mice bearing ALKF1174L/MYCN-positive neuroblastoma. Here, we investigated the molecular basis of this effect and assessed whether a similar strategy would be effective in ALK-mutated tumors lacking MYCN overexpression. We show that in ALK-mutated, MYCN-amplified neuroblastoma cells, crizotinib alone does not affect mTORC1 activity as indicated by persistent RPS6 phosphorylation. Combined treatment with crizotinib and an ATP-competitive mTOR inhibitor abrogated RPS6 phosphorylation, leading to reduced tumor growth and prolonged survival in ALKF1174L/MYCN-positive models compared to single agent treatment. By contrast, this combination, while inducing mTORC1 downregulation, caused reciprocal upregulation of PI3K activity in ALK-mutated cells expressing wild-type MYCN. Here, an inhibitor with potency against both mTOR and PI3K was more effective in promoting cytotoxicity when combined with crizotinib. Our findings should enable a more precise selection of molecularly targeted agents for patients with ALK-mutated tumors.

An investigation of thermal lensing effects in longitudinally diode-pumped Nd:YVO 4 lasers is made in detail both numerically and experimentally. A finite-element model is used to theoretically simulate thermal lensing in various Nd:YVO 4 crystals and pumping scenarios. The predicted values for thermally induced lens strengths are compared with experimentally observed results. We find that these two sets of results are in broad agreement, provided that the spatial profile of the pump-induced heat generation is accurately modeled. The saturation of the pump absorption is found to be of particular importance in producing an accurate prediction of the thermal lens strength, and a composite structure of the crystals is desirable to relieve the thermal lensing.Index Terms-Composite crystal, diode-pumped laser, Nd:YVO 4 , thermal effect, thermal lensing.

Neoplastic epithelia may remain dormant and clinically unapparent in human patients for decades. Multiple risk factors including mutations in tumor cells or the stromal cells may affect the switch from dormancy to malignancy. Gene mutations, including p53 mutations, within the stroma of tumors are associated with a worse clinical prognosis; however, it is not known if these stromal mutations can promote tumors in genetically at-risk tissue. To address this question, ApcMin/+ and Apc Min/+ Rag2 −/− mice, which have a predilection to mammary carcinoma (as well as wild-type (wt) mice), received mesenchymal stem cells (MSC) with mutant p53 (p53MSC) transferred via tail vein injection. In the wt mouse, p53MSC circulated in the periphery and homed to the marrow cavity where they could be recovered up to a year later without apparent effect on the health of the mouse. No mammary tumors were found. However, in mice carrying the Apc Min/+ mutation, p53MSC homed to mammary tissue and signifi cantly increased the incidence of mammary carcinoma. Tumor necrosis factor (TNF)-α-dependent factors elaborated from mesenchymal cells converted quiescent epithelia into clinically apparent disease. The increased cancer phenotype was completely preventable with neutralization of TNF-α or by transfer of CD4+ regulatory T cells from immune competent donors, demonstrating that immune competency to regulate infl ammation was suffi cient to maintain neoplastic dormancy even in the presence of oncogenic epithelial and stromal mutations. The signifi cant synergy between host immunity and mesenchymal cells identifi ed here may restructure treatments to restore an anticancer microenvironment.