Discovering dominant tumor immune archetypes in a pan-cancer census.

Cancers display significant heterogeneity with respect to tissue of origin, driver mutations, and other features of the surrounding tissue. It is likely that individual tumors engage common patterns of the immune system-here "archetypes"-creating prototypical non-destructive tumor immune microenvironments (TMEs) and modulating tumor-targeting. To discover the dominant immune system archetypes, the University of California, San Francisco (UCSF) Immunoprofiler Initiative (IPI) processed 364 individual tumors across 12 cancer types using standardized protocols. Computational clustering of flow cytometry and transcriptomic data obtained from cell sub-compartments uncovered dominant patterns of immune composition across cancers. These archetypes were profound insofar as they also differentiated tumors based upon unique immune and tumor gene-expression patterns. They also partitioned well-established classifications of tumor biology. The IPI resource provides a template for understanding cancer immunity as a collection of dominant patterns of immune organization and provides a rational path forward to learn how to modulate these to improve therapy.

Therapy-Induced Evolution of Human Lung Cancer Revealed by Single-Cell RNA Sequencing.

Lung cancer, the leading cause of cancer mortality, exhibits heterogeneity that enables adaptability, limits therapeutic success, and remains incompletely understood. Single-cell RNA sequencing (scRNA-seq) of metastatic lung cancer was performed using 49 clinical biopsies obtained from 30 patients before and during targeted therapy. Over 20,000 cancer and tumor microenvironment (TME) single-cell profiles exposed a rich and dynamic tumor ecosystem. scRNA-seq of cancer cells illuminated targetable oncogenes beyond those detected clinically. Cancer cells surviving therapy as residual disease (RD) expressed an alveolar-regenerative cell signature suggesting a therapy-induced primitive cell-state transition, whereas those present at on-therapy progressive disease (PD) upregulated kynurenine, plasminogen, and gap-junction pathways. Active T-lymphocytes and decreased macrophages were present at RD and immunosuppressive cell states characterized PD. Biological features revealed by scRNA-seq were biomarkers of clinical outcomes in independent cohorts. This study highlights how therapy-induced adaptation of the multi-cellular ecosystem of metastatic cancer shapes clinical outcomes.

Perioperative Lung Resection Outcomes After Implementation of a Multidisciplinary, Evidence-based Thoracic ERAS Program.

OBJECTIVE: This prospective study evaluated perioperative lung resection outcomes after implementation of a multidisciplinary, evidence-based Thoracic Enhanced Recovery After Surgery (ERAS) Program in an academic, quaternary-care center. BACKGROUND: ERAS programs have the potential to improve outcomes, but have not been widely utilized in thoracic surgery. METHODS: In all, 295 patients underwent elective lung resection for pulmonary malignancy from 2015 to 2019 PRE (n = 169) and POST (n = 126) implementation of an ERAS program containing all major ERAS Society guidelines. Propensity score-matched analysis, based upon patient, tumor, and surgical characteristics, was utilized to evaluate outcomes. RESULTS: After ERAS implementation, there was increased minimally invasive surgery (PRE 39.6%→POST 62.7%), reduced intensive care unit utilization (PRE 70.4%→POST 21.4%), improved chest tube (PRE 24.3%→POST 54.8%) and urinary catheter (PRE 20.1%→POST 65.1%) removal by postoperative day 1, and increased ambulation ≥3× on postoperative day 1 (PRE 46.8%→POST 54.8%). Propensity score-matched analysis that accounted for minimally invasive surgery demonstrated that program implementation reduced length of stay by 1.2 days [95% confidence interval (CI) 0.3-2.0; PRE 4.4→POST 3.2), morbidity by 12.0% (95% CI 1.6%-22.5%; PRE 32.0%→POST 20.0%), opioid use by 19 oral morphine equivalents daily (95% CI 1-36; PRE 101→POST 82), and the direct costs of surgery and hospitalization by $3500 (95% CI $1100-5900; PRE $23,000→POST $19,500). Despite expedited discharge, readmission remained unchanged (PRE 6.3%→POST 6.6%; P = 0.94). CONCLUSIONS: The Thoracic ERAS Program for lung resection reduced length of stay, morbidity, opioid use, and direct costs without change in readmission. This is the first external validation of the ERAS Society thoracic guidelines; adoption by other centers may show similar benefit.

Resectability, Recurrence, and Risk Stratification of Giant Solitary Fibrous Tumors in the Thoracic Cavity.

BACKGROUND: Solitary fibrous tumors (SFTs) are rare mesenchymal tumors most commonly arising from the pleura in the thoracic cavity. The impact of tumor size on risk of recurrence in thoracic SFTs is not well understood. METHODS: A single institution review was performed on all resected thoracic SFTs (1992-2019) with giant SFT defined as ≥ 15 cm. Clinical information, pathologic characteristics, and long-term survival data were collected, and predictors of recurrence and survival were evaluated with regression and Kaplan-Meier analysis. RESULTS: There were 38 thoracic SFTs resected from patients, with the majority of tumors (n = 23, 60.5%) originating from visceral pleura. There were nine (23.7%) giant SFTs with a mean size 20.4 cm (range 17-30 cm). Mean follow-up time was 81.0 months (range 1-261 months), during which 4 of 38 (10.5%) patients experienced a recurrence within the thorax (range 51-178 months). The presence of tumor necrosis (p = 0.021) and ≥ 4 mitoses per high-powered field (p = 0.010) were associated with SFT recurrence on univariate regression. Overall 5-year, 10-year, and 20-year survival was 78.2%, 72.6%, and 42.4%, respectively, and SFT-related mortality occurred in three patients at 83, 180, and 208 months postoperatively. There were no recurrences or SFT-related mortality among patients with giant SFT. CONCLUSION: This study represents one of the largest contemporary single institution reviews of long-term outcomes of giant thoracic SFT. Our data suggest that size is not a risk factor for recurrence in thoracic SFTs and long-term survival is excellent for giant SFTs.

Improved outcomes and staging in non-small-cell lung cancer guided by a molecular assay.

There remains a critical need for improved staging of non-small-cell lung cancer, as recurrence and mortality due to undetectable metastases at the time of surgery remain high even after complete resection of tumors currently categorized as 'early stage.' A 14-gene quantitative PCR-based expression profile has been extensively validated to better identify patients at high-risk of 5-year mortality after surgical resection than conventional staging - mortality that almost always results from previously undetectable metastases. Furthermore, prospective studies now suggest a predictive benefit in disease-free survival when the assay is used to guide adjuvant chemotherapy decisions in early-stage non-small-cell lung cancer patients.

Lay abstract There is a need for improvement in the way early-stage non-small-cell lung cancers are staged and treated because many patients with 'early-stage' disease suffer high rates of cancer recurrence after surgery. In recent years, a specialized test has been developed to allow better characterization of a tumor's risk of recurrence based on the genes being expressed by tumor cells. Use of this test, in conjunction with standard staging methods, is better able to identify patients at high risk of cancer recurrence after surgery. Evidence suggests that giving chemotherapy to patients at high risk of recurrence after surgery reduces recurrence rates and improves long-term patient survival.

High risk, high reward: An analysis of outcomes for candidates awaiting hepatic re-transplantation.

 Background. Liver re-transplantation (re-OLT) remains the only feasible option for patients with graft failure following liver transplantation. Sparse resources and a growing waitlist mandate that available grafts are allocated properly. We studied the differences in patient demographics, characteristics, and survival for those listed for re-OLT in a region with prolonged wait times. MATERIAL AND METHODS: We performed a single-center retrospective study, from 2005 to 2013, of adult candidates listed for liver re-OLT at a tertiary care center within United Network for Organ Sharing (UNOS) region 1. RESULTS: Of the 48 patients listed for re-OLT, 1(2%) improved while waiting, 14(29%) died while waiting, and 33(69%) underwent re-OLT. Those re-transplanted represented 11% of the center's adult liver transplant volume during the same time period. Comparing those who died while waiting to those who achieved re-OLT, there was no significant difference in age (median 52 vs. 48 years, p=0.56) or MELD at second listing (median 29 vs. 26, p = 0.90). Waitlisted candidates who failed to achieve re-transplant died on average of 15.5 days (IQR 36 days) days after re-listing. Those re-transplanted achieved 3-year survival of 70% and there was no significant difference in 3-year survival of those re-transplanted within or beyond 90 days of first transplant (70% vs. 69.5%, p = 0.28). CONCLUSIONS: In conclusion, re-OLT is the only viable option for candidates with nonreversible liver graft failure. Inability to achieve re-OLT leads to nearly assured and expeditious death. Despite technical challenges, in experienced hands excellent long term survival following re-OLT can be achieved.

A practical molecular assay to predict survival in resected non-squamous, non-small-cell lung cancer: development and international validation studies.

BACKGROUND: The frequent recurrence of early-stage non-small-cell lung cancer (NSCLC) is generally attributable to metastatic disease undetected at complete resection. Management of such patients depends on prognostic staging to identify the individuals most likely to have occult disease. We aimed to develop and validate a practical, reliable assay that improves risk stratification compared with conventional staging. METHODS: A 14-gene expression assay that uses quantitative PCR, runs on formalin-fixed paraffin-embedded tissue samples, and differentiates patients with heterogeneous statistical prognoses was developed in a cohort of 361 patients with non-squamous NSCLC resected at the University of California, San Francisco. The assay was then independently validated by the Kaiser Permanente Division of Research in a masked cohort of 433 patients with stage I non-squamous NSCLC resected at Kaiser Permanente Northern California hospitals, and on a cohort of 1006 patients with stage I-III non-squamous NSCLC resected in several leading Chinese cancer centres that are part of the China Clinical Trials Consortium (CCTC). FINDINGS: Kaplan-Meier analysis of the Kaiser validation cohort showed 5 year overall survival of 71·4% (95% CI 60·5-80·0) in low-risk, 58·3% (48·9-66·6) in intermediate-risk, and 49·2% (42·2-55·8) in high-risk patients (p(trend)=0·0003). Similar analysis of the CCTC cohort indicated 5 year overall survivals of 74·1% (66·0-80·6) in low-risk, 57·4% (48·3-65·5) in intermediate-risk, and 44·6% (40·2-48·9) in high-risk patients (p(trend)<0·0001). Multivariate analysis in both cohorts indicated that no standard clinical risk factors could account for, or provide, the prognostic information derived from tumour gene expression. The assay improved prognostic accuracy beyond National Comprehensive Cancer Network criteria for stage I high-risk tumours (p<0·0001), and differentiated low-risk, intermediate-risk, and high-risk patients within all disease stages. INTERPRETATION: Our practical, quantitative-PCR-based assay reliably identified patients with early-stage non-squamous NSCLC at high risk for mortality after surgical resection. FUNDING: UCSF Thoracic Oncology Laboratory and Pinpoint Genomics.

The role of stem cells in airway repair: implications for the origins of lung cancer.

Lung cancer is the leading cause of cancer-related deaths worldwide. Recently, advancements in our ability to identify and study stem cell populations in the lung have helped researchers to elucidate the central role that cells with stem cell-like properties may have in lung tumorigenesis. Much of this research has focused on the use of the airway repair model to study response to injury. In this review, we discuss the primary evidence of the role that cancer stem cells play in lung cancer development. The implications of a stem cell origin of lung cancer are reviewed, and the importance of ongoing research to identify novel therapeutic and prognostic targets is reiterated.

Transcriptional space-time mapping identifies concerted immune and stromal cell patterns and gene programs in wound healing and cancer.

Tissue repair responses in metazoans are highly coordinated by different cell types over space and time. However, comprehensive single-cell-based characterization covering this coordination is lacking. Here, we captured transcriptional states of single cells over space and time during skin wound closure, revealing choreographed gene-expression profiles. We identified shared space-time patterns of cellular and gene program enrichment, which we call multicellular "movements" spanning multiple cell types. We validated some of the discovered space-time movements using large-volume imaging of cleared wounds and demonstrated the value of this analysis to predict "sender" and "receiver" gene programs in macrophages and fibroblasts. Finally, we tested the hypothesis that tumors are like "wounds that never heal" and found conserved wound healing movements in mouse melanoma and colorectal tumor models, as well as human tumor samples, revealing fundamental multicellular units of tissue biology for integrative studies.

Comparative genomics between matched solid and lepidic portions of semi-solid lung adenocarcinomas.

BACKGROUND: Genetic changes that drive the transition from lepidic to invasive cancer development within a radiographic ground glass or semi-solid lung lesion (SSL) are not well understood. Biomarkers to predict the transition to solid, invasive cancer within SSL are needed. METHODS: Patients with surgically resected SSL were identified retrospectively from a surgical database. Clinical characteristics and survival were compared between stage I SSL (n = 65) and solid adenocarcinomas (n = 120) resected during the same time period. Areas of normal lung, in situ lepidic, and invasive solid tumor were microdissected from within the same SSL specimens and next generation sequencing (NGS) and Affymetrix microarray of gene expression were performed. RESULTS: There were more never smokers, Asian patients, and sub-lobar resections among SSL but no difference in 5-year survival between SSL and solid adenocarcinoma. Driver mutations found in both lepidic and solid invasive portion were EGFR (43%), KRAS (21%), and DNMT3A (5%). CEACAM5 was the most upregulated gene found in solid, invasive portions of SSL. Lepidic and invasive solid areas had many similarities in gene expression, however there were some significant differences with the gene SPP1 being a unique biomarker for the invasive component of a SSL. CONCLUSIONS: Common lung cancer driver mutations are present in in situ lepidic as well as invasive solid portions of a SSL, suggesting early development of driver mutations. CEACAM5 and SPP1 emerged as promising biomarkers of invasive potential in semi-solid lesions. Other studies have shown both genes to correlate with poor prognosis in lung cancer and their role in evolution of semi-solid lung lesions warrants further study.

SARS-CoV-2 infection of airway organoids reveals conserved use of Tetraspanin-8 by Ancestral, Delta, and Omicron variants.

Ancestral SARS coronavirus-2 (SARS-CoV-2) and variants of concern (VOC) caused a global pandemic with a spectrum of disease severity. The mechanistic explaining variations related to airway epithelium are relatively understudied. Here, we biobanked airway organoids (AO) by preserving stem cell function. We optimized viral infection with H1N1/PR8 and comprehensively characterized epithelial responses to SARS-CoV-2 infection in phenotypically stable AO from 20 different subjects. We discovered Tetraspanin-8 (TSPAN8) as a facilitator of SARS-CoV-2 infection. TSPAN8 facilitates SARS-CoV-2 infection rates independently of ACE2-Spike interaction. In head-to-head comparisons with Ancestral SARS-CoV-2, Delta and Omicron VOC displayed lower overall infection rates of AO but triggered changes in epithelial response. All variants shared highest tropism for ciliated and goblet cells. TSPAN8-blocking antibodies diminish SARS-CoV-2 infection and may spur novel avenues for COVID-19 therapy.

Bioinformatic Approaches to Validation and Functional Analysis of 3D Lung Cancer Models.

3D models of cancer have the potential to improve basic, translational, and clinical studies. Patient-derived xenografts, spheroids, and organoids are broad categories of 3D models of cancer, and to date, these 3D models of cancer have been established for a variety of cancer types. In lung cancer, for example, 3D models offer a promising new avenue to gain novel insights into lung tumor biology and improve outcomes for patients afflicted with the number one cancer killer worldwide. However, the adoption and utility of these 3D models of cancer vary, and demonstrating the fidelity of these models is a critical first step before seeking meaningful applications. Here, we review use cases of current 3D lung cancer models and bioinformatic approaches to assessing model fidelity. Bioinformatics approaches play a key role in both validating 3D lung cancer models and high dimensional functional analyses to support downstream applications.

Genetic and immunologic features of recurrent stage I lung adenocarcinoma.

Although surgery for early-stage lung cancer offers the best chance of cure, recurrence still occurs between 30 and 50% of the time. Why patients frequently recur after complete resection of early-stage lung cancer remains unclear. Using a large cohort of stage I lung adenocarcinoma patients, distinct genetic, genomic, epigenetic, and immunologic profiles of recurrent tumors were analyzed using a novel recurrence classifier. To characterize the tumor immune microenvironment of recurrent stage I tumors, unique tumor-infiltrating immune population markers were identified using single cell RNA-seq on a separate cohort of patients undergoing stage I lung adenocarcinoma resection and applied to a large study cohort using digital cytometry. Recurrent stage I lung adenocarcinomas demonstrated higher mutation and lower methylation burden than non-recurrent tumors, as well as widespread activation of known cancer and cell cycle pathways. Simultaneously, recurrent tumors displayed downregulation of immune response pathways including antigen presentation and Th1/Th2 activation. Recurrent tumors were depleted in adaptive immune populations, and depletion of adaptive immune populations and low cytolytic activity were prognostic of stage I recurrence. Genomic instability and impaired adaptive immune responses are key features of stage I lung adenocarcinoma immunosurveillance escape and recurrence after surgery.

Molecular Risk Stratification is Independent of EGFR Mutation Status in Identifying Early-Stage Non-Squamous Non-Small Cell Lung Cancer Patients at Risk for Recurrence and Likely to Benefit From Adjuvant Chemotherapy.

BACKGROUND: A clinically-certified gene expression profile improved survival in a cohort of stage I-IIA NSCLC patients by identifying those likely to benefit from adjuvant intervention. EGFR mutation status has not provided this type of predictive risk discrimination in stage IA NSCLC, and overtreatment of low-risk stage IB patients may have limited the overall benefit seen recently in the adjuvant application of a third-generation TKI. We compared EGFR mutation data to molecular risk stratification in a prospective, early-stage cohort. MATERIALS AND METHODS: Two hundred fifty eligible stage I-IIA non-squamous NSCLC patients underwent prospective molecular risk stratification by the 14-gene prognostic assay. Platinum doublet adjuvant chemotherapy (AC) was recommended for molecular high-risk (MHR). Differences in freedom from recurrence (FFR) and disease-free survival (DFS) were evaluated. RESULTS: At 29 months, prospective molecular testing yielded an estimated FFR of 94.6% and 72.4% in low-risk and untreated MHR patients, respectively, and 97.0% among MHR patients receiving AC (P < .001). In contrast, there was no association between EGFR status and recurrence, while molecular risk predicted survival and response to AC within both the EGFR mutation(+) and mutation(-) populations. Sixty-seven percent of EGFR(+) and 49% of EGFR(-) patients were molecular low-risk. CONCLUSION: This prospective study demonstrates the utility of the 14-gene assay independent of EGFR mutation. Basing adjuvant intervention in early-stage NSCLC on EGFR status alone may undertreat up to 51% of EGFR(-) patients likely to benefit from adjuvant intervention, and overtreat as many as 67% of EGFR(+) patients more likely to be free of residual disease.

SARS-CoV-2 infection studies in lung organoids identify TSPAN8 as novel mediator.

SARS coronavirus-2 (SARS-CoV-2) is causing a global pandemic with large variation in COVID-19 disease spectrum. SARS-CoV-2 infection requires host receptor ACE2 on lung epithelium, but epithelial underpinnings of variation are largely unknown. We capitalized on comprehensive organoid assays to report remarkable variation in SARS-CoV-2 infection rates of lung organoids from different subjects. Tropism is highest for TUBA- and MUC5AC-positive organoid cells, but levels of TUBA-, MUC5A-, or ACE2- positive cells do not predict infection rate. We identify surface molecule Tetraspanin 8 (TSPAN8) as novel mediator of SARS-CoV-2 infection, which is not downregulated by this specific virus. TSPAN8 levels, prior to infection, strongly correlate with infection rate and TSPAN8-blocking antibodies diminish SARS-CoV-2 infection. We propose TSPAN8 as novel functional biomarker and potential therapeutic target for COVID-19.

Applications of Next-Generation Sequencing in Neoantigen Prediction and Cancer Vaccine Development.

Next-generation sequencing has changed the face of cancer immunotherapy research by making tumor-specific cancer vaccines a reality. Whole exome sequencing and RNA sequencing combined with bioinformatic pipelines allow the prediction of neoantigen targets for cancer vaccines. In this review, we discuss the preclinical and early clinical evidence for cancer vaccines; describe methods and challenges in neoantigen prediction; and summarize emerging new technologies that will improve neoantigen cancer vaccine development.

Integration of flow-dependent endothelial phenotypes by Kruppel-like factor 2.

In the face of systemic risk factors, certain regions of the arterial vasculature remain relatively resistant to the development of atherosclerotic lesions. The biomechanically distinct environments in these arterial geometries exert a protective influence via certain key functions of the endothelial lining; however, the mechanisms underlying the coordinated regulation of specific mechano-activated transcriptional programs leading to distinct endothelial functional phenotypes have remained elusive. Here, we show that the transcription factor Kruppel-like factor 2 (KLF2) is selectively induced in endothelial cells exposed to a biomechanical stimulus characteristic of atheroprotected regions of the human carotid and that this flow-mediated increase in expression occurs via a MEK5/ERK5/MEF2 signaling pathway. Overexpression and silencing of KLF2 in the context of flow, combined with findings from genome-wide analyses of gene expression, demonstrate that the induction of KLF2 results in the orchestrated regulation of endothelial transcriptional programs controlling inflammation, thrombosis/hemostasis, vascular tone, and blood vessel development. Our data also indicate that KLF2 expression globally modulates IL-1beta-mediated endothelial activation. KLF2 therefore serves as a mechano-activated transcription factor important in the integration of multiple endothelial functions associated with regions of the arterial vasculature that are relatively resistant to atherogenesis.

Genomic prognostic models in early-stage lung cancer.

Patients with early-stage lung cancer demonstrate significant recurrence rates and lower-than-expected survival rates after surgical resection, indicating that our current staging methods do not adequately predict outcome. Since the last revision of the TNM staging system, a number of genomic models have been proposed which more accurately predict prognosis in patients with early-stage lung cancer. A variety of prognostic genomic models based on gene-expression profiling and quantitative polymerase chain reaction (PCR) are able to stratify patients with early-stage lung cancer into high- and low-risk groups with respect to disease-free and overall survival. In the future, clinical application of these models may ultimately dictate both the use of adjuvant therapy as well as the choice of surgical procedure in patients with early-stage lung cancer. An effort to develop a robust genomic model for use in the clinical setting should be prompted by encouraging results obtained by the use of a quantitative PCR-based genomic signature in the field of breast oncology.

Comparison of Conventional TNM and Novel TNMB Staging Systems for Non-Small Cell Lung Cancer.

Importance: Improved staging for non-small cell lung cancer (NSCLC) represents a critical unmet need. External validations of the eighth edition of the TNM staging system have yielded disappointing results, with persistently high mortality observed in early-stage disease. Objective: To determine whether incorporation of a molecular prognostic classifier into conventional TNM staging for NSCLC improves estimation of disease-free survival. Design, Setting, and Participants: This cohort study was conducted at an academic, quaternary care medical center from 2012 to 2018. A consecutive series of 238 patients underwent surgical resection of stage I to IIIC nonsquamous NSCLC and had molecular prognostic classifier testing performed. Data analysis was conducted in May 2019. Exposures: Patients were restaged according to the seventh and eighth editions of the TNM staging system and the novel TMMB staging system, which maintains the order and structure of the eighth edition of the TNM but downstages or upstages according to low or high molecular risk, respectively. Main Outcomes and Measures: The primary outcome was disease-free survival 3 years from the time of surgical resection. Reclassification statistics were then used to evaluate performance and improvement measures of the TNM seventh and eighth editions and the TNMB staging system. Results: Two hundred thirty-eight patients (144 [60.5%] female; median [interquartile range] age, 70 [63-75] years) were analyzed. The median (interquartile range) follow-up was 25 (14-40) months, and the disease-free survival rate was estimated to be 58.3% (95% CI, 45.7% to 69.0%). One hundred fifty-nine patients (66.8%) were reclassified by the TNMB staging system. Overall model fit remained the same for the seventh and eighth editions of the TNM staging system, whereas the R2 statistic (change from 0.22 to 0.31), concordance index (change from 0.68 to 0.73), and log-rank χ2 (change from 38 to 108) were all associated with improvements after TNMB adoption. The TNMB system, compared with the TNM eighth edition, was associated with enhanced identification of high-risk patients and better differentiation of those without recurrence from those who had recurrence (net reclassification improvement, 0.28; 95% CI, 0.08 to 0.46; P < .001), whereas the eighth edition compared with the seventh edition was not associated with improvement of this measure (net reclassification improvement, 0.02; 95% CI, -0.18 to 0.21; P = .87). Conclusions and Relevance: The TNMB staging system was associated with improved estimation of disease-free survival compared with conventional TNM staging. Incorporation of a molecular prognostic classifier into staging for NSCLC may lead to better identification of high-risk patients.

Differential gene expression identifies KRT7 and MUC1 as potential metastasis-specific targets in sarcoma.

BACKGROUND: Despite numerous discoveries regarding the molecular genesis and progression of primary cancers, the biology of metastasis remains poorly understood. Compared to very large numbers of circulating tumor cells that are now known to accompany nearly all cancers, a relatively limited number of lesions actually develop in most patients with metastases. We hypothesized that phenotypic changes driven by differential gene expression in a finite subpopulation of tumor cells render those cells capable of metastasis and sought to identify key pathways through analysis of gene expression in primary and metastatic lesions from the same patients. METHODS: We compared whole-genome expression in 4 matched samples of primary and metastatic sarcoma, then evaluated candidate genes with differential expression via quantitative PCR in 30 additional matched sets, tumor tissue immunostaining, siRNA loss-of-function in a sarcoma cell migration assay, and clinical correlation with overall and disease-free survival after metastasectomy. RESULTS: Comparison of microarray signals identified differential expression of cell adhesion genes, including upregulation of KRT7 and MUC1 in metastases; KRT7 and MUC1 upregulation was confirmed in 22 (73%) and 20 (67%) matched sets of metastatic/primary tumors, respectively. Silencing of KRT7 and MUC1 via targeted siRNAs suppressed sarcoma cell migration in vitro, and a significant correlation (two-sided) was observed between both KRT7 and MUC1 expression in metastases and overall patient survival. CONCLUSION: KRT7 and MUC1 may play a significant role in enabling sarcoma metastasis, and they may therefore be important prognostic biomarkers as well as potential targets for therapeutic prevention of metastasis.