Clonal dominance defines metastatic dissemination in pancreatic cancer.

Tumors represent ecosystems where subclones compete during tumor growth. While extensively investigated, a comprehensive picture of the interplay of clonal lineages during dissemination is still lacking. Using patient-derived pancreatic cancer cells, we created orthotopically implanted clonal replica tumors to trace clonal dynamics of unperturbed tumor expansion and dissemination. This model revealed the multifaceted nature of tumor growth, with rapid changes in clonal fitness leading to continuous reshuffling of tumor architecture and alternating clonal dominance as a distinct feature of cancer growth. Regarding dissemination, a large fraction of tumor lineages could be found at secondary sites each having distinctive organ growth patterns as well as numerous undescribed behaviors such as abortive colonization. Paired analysis of primary and secondary sites revealed fitness as major contributor to dissemination. From the analysis of pro- and nonmetastatic isogenic subclones, we identified a transcriptomic signature able to identify metastatic cells in human tumors and predict patients' survival.

Targeting DNA2 overcomes metabolic reprogramming in multiple myeloma.

DNA damage resistance is a major barrier to effective DNA-damaging therapy in multiple myeloma (MM). To discover mechanisms through which MM cells overcome DNA damage, we investigate how MM cells become resistant to antisense oligonucleotide (ASO) therapy targeting Interleukin enhancer binding factor 2 (ILF2), a DNA damage regulator that is overexpressed in 70% of MM patients whose disease has progressed after standard therapies have failed. Here, we show that MM cells undergo adaptive metabolic rewiring to restore energy balance and promote survival in response to DNA damage activation. Using a CRISPR/Cas9 screening strategy, we identify the mitochondrial DNA repair protein DNA2, whose loss of function suppresses MM cells' ability to overcome ILF2 ASO-induced DNA damage, as being essential to counteracting oxidative DNA damage. Our study reveals a mechanism of vulnerability of MM cells that have an increased demand for mitochondrial metabolism upon DNA damage activation.

Ether phospholipids are required for mitochondrial reactive oxygen species homeostasis.

Mitochondria are hubs where bioenergetics, redox homeostasis, and anabolic metabolism pathways integrate through a tightly coordinated flux of metabolites. The contributions of mitochondrial metabolism to tumor growth and therapy resistance are evident, but drugs targeting mitochondrial metabolism have repeatedly failed in the clinic. Our study in pancreatic ductal adenocarcinoma (PDAC) finds that cellular and mitochondrial lipid composition influence cancer cell sensitivity to pharmacological inhibition of electron transport chain complex I. Profiling of patient-derived PDAC models revealed that monounsaturated fatty acids (MUFAs) and MUFA-linked ether phospholipids play a critical role in maintaining ROS homeostasis. We show that ether phospholipids support mitochondrial supercomplex assembly and ROS production; accordingly, blocking de novo ether phospholipid biosynthesis sensitized PDAC cells to complex I inhibition by inducing mitochondrial ROS and lipid peroxidation. These data identify ether phospholipids as a regulator of mitochondrial redox control that contributes to the sensitivity of PDAC cells to complex I inhibition.

Targeting DNA2 Overcomes Metabolic Reprogramming in Multiple Myeloma.

DNA damage resistance is a major barrier to effective DNA-damaging therapy in multiple myeloma (MM). To discover novel mechanisms through which MM cells overcome DNA damage, we investigated how MM cells become resistant to antisense oligonucleotide (ASO) therapy targeting ILF2, a DNA damage regulator that is overexpressed in 70% of MM patients whose disease has progressed after standard therapies have failed. Here, we show that MM cells undergo an adaptive metabolic rewiring and rely on oxidative phosphorylation to restore energy balance and promote survival in response to DNA damage activation. Using a CRISPR/Cas9 screening strategy, we identified the mitochondrial DNA repair protein DNA2, whose loss of function suppresses MM cells' ability to overcome ILF2 ASO-induced DNA damage, as being essential to counteracting oxidative DNA damage and maintaining mitochondrial respiration. Our study revealed a novel vulnerability of MM cells that have an increased demand for mitochondrial metabolism upon DNA damage activation. STATEMENT OF SIGNIFICANCE: Metabolic reprogramming is a mechanism through which cancer cells maintain survival and become resistant to DNA-damaging therapy. Here, we show that targeting DNA2 is synthetically lethal in myeloma cells that undergo metabolic adaptation and rely on oxidative phosphorylation to maintain survival after DNA damage activation.

Immune landscape of a genetically engineered murine model of glioma compared with human glioma.

Novel therapeutic strategies targeting glioblastoma (GBM) often fail in the clinic, partly because preclinical models in which hypotheses are being tested do not recapitulate human disease. To address this challenge, we took advantage of our previously developed spontaneous Qk/Trp53/Pten (QPP) triple-knockout model of human GBM, comparing the immune microenvironment of QPP mice with that of patient-derived tumors to determine whether this model provides opportunity for gaining insights into tumor physiopathology and preclinical evaluation of therapeutic agents. Immune profiling analyses and single-cell sequencing of implanted and spontaneous tumors from QPP mice and from patients with glioma revealed intratumoral immune components that were predominantly myeloid cells (e.g., monocytes, macrophages, and microglia), with minor populations of T, B, and NK cells. When comparing spontaneous and implanted mouse samples, we found more neutrophils and T and NK cells in the implanted model. Neutrophils and T and NK cells were increased in abundance in samples derived from human high-grade glioma compared with those derived from low-grade glioma. Overall, our data demonstrate that our implanted and spontaneous QPP models recapitulate the immunosuppressive myeloid-dominant nature of the tumor microenvironment of human gliomas. Our model provides a suitable tool for investigating the complex immune compartment of gliomas.

Medium-Chain Acyl-CoA Dehydrogenase Protects Mitochondria from Lipid Peroxidation in Glioblastoma.

Glioblastoma (GBM) is highly resistant to chemotherapies, immune-based therapies, and targeted inhibitors. To identify novel drug targets, we screened orthotopically implanted, patient-derived glioblastoma sphere-forming cells using an RNAi library to probe essential tumor cell metabolic programs. This identified high dependence on mitochondrial fatty acid metabolism. We focused on medium-chain acyl-CoA dehydrogenase (MCAD), which oxidizes medium-chain fatty acids (MCFA), due to its consistently high score and high expression among models and upregulation in GBM compared with normal brain. Beyond the expected energetics impairment, MCAD depletion in primary GBM models induced an irreversible cascade of detrimental metabolic effects characterized by accumulation of unmetabolized MCFAs, which induced lipid peroxidation and oxidative stress, irreversible mitochondrial damage, and apoptosis. Our data uncover a novel protective role for MCAD to clear lipid molecules that may cause lethal cell damage, suggesting that therapeutic targeting of MCFA catabolism may exploit a key metabolic feature of GBM. SIGNIFICANCE: MCAD exerts a protective role to prevent accumulation of toxic metabolic by-products in glioma cells, actively catabolizing lipid species that would otherwise affect mitochondrial integrity and induce cell death. This work represents a first demonstration of a nonenergetic role for dependence on fatty acid metabolism in cancer.This article is highlighted in the In This Issue feature, p. 2659.

Syndecan 1 is a critical mediator of macropinocytosis in pancreatic cancer.

Pancreatic ductal adenocarcinoma (PDAC) remains recalcitrant to all forms of cancer treatment and carries a five-year survival rate of only 8%1. Inhibition of oncogenic KRAS (hereafter KRAS*), the earliest lesion in disease development that is present in more than 90% of PDACs, and its signalling surrogates has yielded encouraging preclinical results with experimental agents2-4. However, KRAS*-independent disease recurrence following genetic extinction of Kras* in mouse models anticipates the need for co-extinction strategies5,6. Multiple oncogenic processes are initiated at the cell surface, where KRAS* physically and functionally interacts to direct signalling that is essential for malignant transformation and tumour maintenance. Insights into the complexity of the functional cell-surface-protein repertoire (surfaceome) have been technologically limited until recently and-in the case of PDAC-the genetic control of the function and composition of the PDAC surfaceome in the context of KRAS* signalling remains largely unknown. Here we develop an unbiased, functional target-discovery platform to query KRAS*-dependent changes of the PDAC surfaceome, which reveals syndecan 1 (SDC1, also known as CD138) as a protein that is upregulated at the cell surface by KRAS*. Localization of SDC1 at the cell surface-where it regulates macropinocytosis, an essential metabolic pathway that fuels PDAC cell growth-is essential for disease maintenance and progression. Thus, our study forges a mechanistic link between KRAS* signalling and a targetable molecule driving nutrient salvage pathways in PDAC and validates oncogene-driven surfaceome annotation as a strategy to identify cancer-specific vulnerabilities.

Valuation of the economic benefits of human papillomavirus vaccine in Taiwan.

OBJECTIVES: The study aims to apply the contingent valuation method to elicit the willingness-to-pay (WTP), and measure the value of a statistic life (VSL), for human papillomavirus (HPV) vaccine in Taiwan. METHODS: A total of 512 questionnaires were completed on women aged 20 to 55 years with at least one daughter, during March through May 2007. The respondents' WTP for the vaccines was elicited by double-bounded binary-choice questions under two scenarios: one was to protect themselves from cervical cancer (CC) and the other was for their daughter(s). The WTP was modeled as a function of the respondents' knowledge score, attitudes toward CC and HPV vaccine, the vaccination outcome scenarios, and individual characteristics. A log-normal survival model was constructed and the maximum-likelihood method was used for estimation. RESULTS: The median regression-adjusted WTP was estimated at US$1098 to US$1233 (US$913-1004) for vaccinating the daughter (mother); and the VSL was estimated at approximately US$0.65 to US$4.09 (US$0.56-3.16) million for vaccinating the daughter (mother). CONCLUSIONS: The study results provided important evidences on the monetary value women placed on a HPV vaccine, and the differential benefits between vaccinating the women and their daughters.

Hospital ownership and performance: evidence from stroke and cardiac treatment in Taiwan.

This paper compares program expenditure and treatment quality of stroke and cardiac patients between 1997 and 2000 across hospitals of various ownership types in Taiwan. Because Taiwan implemented national health insurance in 1995, the analysis is immune from problems arising from the complex setting of the U.S. health care market, such as segmentation of insurance status or multiple payers. Because patients may select admitted hospitals based on their observed and unobserved characteristics, we employ instrument variable (IV) estimation to account for the endogeneity of ownership status. Results of IV estimation find that patients admitted to non-profit hospitals receive better quality care, either measured by 1- or 12-month mortality rates. In terms of treatment expenditure, our results indicate no difference between non-profits and for-profits index admission expenditures, and at most 10% higher long-term expenditure for patients admitted to non-profits than to for-profits.

Willingness to pay for drug abuse treatment: results from a contingent valuation study in Taiwan.

OBJECTIVE: In this study, we attempted to describe and justify the use of a contingent valuation (CV) method to elicit the willingness to pay (WTP) for a drug abuse treatment program by the general public in Taiwan. METHOD: In total, 1817 CV survey questionnaires were conducted through telephone interviews from randomly dialed numbers. Subjects were members of the general public aged between 20 and 65 years, with full-time jobs, and residing in the three major Taiwanese cities of Taipei, Taichung, and Kaohsiung. Respondents' WTP for drug treatment programs was elicited for two different financing mechanisms: payment through 'compulsory' payroll tax/health insurance premiums, and through 'voluntary' donations. The WTP was modeled as a function of scenarios and policies of the treatment program, respondents' socio-demographic information, and their responses to knowledge and attitudes questions. RESULTS: The general public in Taiwan was estimated to be willing to pay between NT$81.00 and NT$95.00 per month for a drug abuse treatment program, while the benefits of drug abuse treatment were estimated to range between NT$12.8 billion and NT$15.0 billion in 2004 (US$1=NT$31.9 in 2004), which was equal to around 0.15% of Taiwan's GDP for that year. The general public in Taiwan was more willing to pay for drug abuse treatment via increases in NHI premiums than via donations. Preferences for the drug abuse treatment program were also found to be sensitive to the target treated population as well as the sequence in which the WTP questions were asked. CONCLUSIONS: Results of this study provide policymakers with important evidence on the monetary value of a substance abuse treatment program, allocation of healthcare resources, and a possible financing mechanism of the treatment program, which may be justified by knowledge of the WTP of the general public. This study has also advanced the knowledge of the methodological issues with regard to CV questionnaire design, and it provides a base case for further studies on drug abuse in Taiwan.