Faculty Bibliography

We report a protocol for obtaining high-quality single-cell transcriptomics data from human lung biospecimens acquired from core needle biopsies, fine-needle aspirates, surgical resection, and pleural effusions. The protocol relies upon the brief mechanical and enzymatic disruption of tissue, enrichment of live cells by fluorescence-activated cell sorting (FACS), and droplet-based single-cell RNA sequencing (scRNA-seq). The protocol also details a procedure for analyzing the scRNA-seq data. For complete details on the use and execution of this protocol, please refer to Chan et al. (2021).

BACKGROUND:Diffuse pleural mesothelioma (DPM) is an aggressive malignancy that, despite recent treatment advances, has unacceptably poor outcomes. Therapeutic research in DPM is inhibited by a paucity of preclinical models that faithfully recapitulate the human disease. METHODS:We established 22 patient-derived xenografts (PDX) from 22 patients with DPM and performed multi-omic analyses to deconvolute the mutational landscapes, global expression profiles, and molecular subtypes of these PDX models and compared features to those of the matched primary patient tumors. Targeted next-generation sequencing (NGS; MSK-IMPACT), immunohistochemistry, and histologic subtyping were performed on all available samples. RNA sequencing was performed on all available PDX samples. Clinical outcomes and treatment history were annotated for all patients. Platinum-doublet progression-free survival (PFS) was determined from the start of chemotherapy until radiographic/clinical progression and grouped into < or ≥ 6 months. RESULTS:PDX models were established from both treatment naïve and previously treated samples and were noted to closely resemble the histology, genomic landscape, and proteomic profiles of the parent tumor. After establishing the validity of the models, transcriptomic analyses demonstrated overexpression in WNT/β-catenin, hedgehog, and TGF-β signaling and a consistent suppression of immune-related signaling in PDXs derived from patients with worse clinical outcomes. CONCLUSIONS:These data demonstrate that DPM PDX models closely resemble the genotype and phenotype of parental tumors, and identify pathways altered in DPM for future exploration in preclinical studies.

Small cell lung cancer (SCLC) is characterized by morphologic, epigenetic and transcriptomic heterogeneity. Subtypes based upon predominant transcription factor expression have been defined that, in mouse models and cell lines, exhibit potential differential therapeutic vulnerabilities, with epigenetically distinct SCLC subtypes also described. The clinical relevance of these subtypes is unclear, due in part to challenges in obtaining tumor biopsies for reliable profiling. Here we describe a robust workflow for genome-wide DNA methylation profiling applied to both patient-derived models and to patients' circulating cell-free DNA (cfDNA). Tumor-specific methylation patterns were readily detected in cfDNA samples from patients with SCLC and were correlated with survival outcomes. cfDNA methylation also discriminated between the transcription factor SCLC subtypes, a precedent for a liquid biopsy cfDNA-methylation approach to molecularly subtype SCLC. Our data reveal the potential clinical utility of cfDNA methylation profiling as a universally applicable liquid biopsy approach for the sensitive detection, monitoring and molecular subtyping of patients with SCLC.

Background: Hepatocyte transplantation is being pursued as an alternative to liver transplantation. This strategy requires hepatocyte proliferation following transplantation, but the extent to which transplanted hepatocytes can proliferate is unknown. Primary human hepatocytes (PHH) from some donors can efficiently humanize liver chimeric mice yet the relative contributions of engraftment and proliferation have not been quantified. We here aimed to define how many PHH engraft after transplantation in chimeric mice and test their proliferation limit.
Method(s): PHH were serially transplanted into immunodeficient Fah-/- mice with liver injury. PHH were transduced with lentiviruses to deliver fluorophores or barcodes prior to transplantation to quantify engraftment and proliferation.
Result(s): On a population level PHH expanded approximately 200-fold per round of transplantation resulting in ~10⁸ cells per liver. Fluorophore labeling showed PHH islands to be of clonal origin. Barcode labeling indicated that approximately 104 cells engrafted per mouse liver. After three rounds of efficient repopulation humanization deteriorated >10-fold per round.
Conclusion(s): PHH can efficiently expand approximately 1012 -fold (104 per transplantation for 3 serial transplantations) in liver chimeric mice, after which their engraftment and/or proliferation potential diminishes. This limit of ~40 cell divisions in mouse livers may guide therapeutic PHH transplantation protocols. (Figure Presented)

Treatment-induced neuroendocrine prostate cancer (NEPC) is a lethal subtype of castration-resistant prostate cancer (CRPC). Using the zirconium-89 (⁸⁹Zr)-labeled DLL3 targeting antibody SC16 (⁸⁹Zr-DFO-SC16), we have developed a positron emission tomography (PET) agent to non-invasively identify the presence of DLL3-positive NEPC lesions. Methods: qPCR and immunohistochemistry were used to compare relative levels of androgen receptor (AR)-regulated markers and NEPC marker DLL3 in a panel of prostate cancer cell lines. PET imaging with ⁸⁹Zr-DFO-SC16, ⁶⁸Ga-PSMA-11, and ⁶⁸Ga-DOTA-TATE was performed in H660 NEPC xenografted male nude mice. ⁸⁹Zr-DFO-SC16 uptake was corroborated by biodistribution studies. Results: In vitro studies demonstrate H660 are positive for DLL3 and negative for AR, prostate-specific antigen (PSA), and prostate-specific membrane antigen (PSMA) both at the transcriptional and translational levels. PET imaging and biodistribution studies confirm ⁸⁹Zr-DFO-SC16 uptake is restricted to H660 tumor xenografts with background uptake in non-NEPC lesions (both AR-dependent and AR-independent). Conversely, H660 xenografts cannot be detected with imaging agents targeting PSMA (⁶⁸Ga-PSMA-11) or somatostatin receptor subtype 2 (SSTR2) (⁶⁸Ga-DOTA-TATE). Conclusion: These studies demonstrate H660 NEPC cells selectively express DLL3 on their cell surface and can be non-invasively identified with ⁸⁹Zr-DFO-SC16.

The microsomal triglyceride transfer protein (MTP) is essential for the secretion of apoB48- and apoB100-containing lipoproteins in the intestine and liver, respectively. Loss of function mutations in MTP cause abetalipoproteinemia. Heterologous cell expression systems are used to evaluate the function of MTP in apoB secretion to avoid background MTP activity in liver and intestine derived cells. However, these systems are not suitable to study the role of MTP in the secretion of apoB100-containing lipoproteins, as expression of a large apoB100 peptide using plasmids is difficult. Here, we report a new cell culture model amenable for studying the role of different MTP mutations on apoB100 secretion. The cell culture system was developed by ablating the endogenous MTTP gene in human hepatoma Huh-7 cells using sgRNA and CRISPR/Cas9 ribonucleoprotein complexes. We successfully established three different clones that did not express any detectable MTTP mRNA, or MTP protein or activity. These cells were defective in secreting apoB-containing lipoproteins, and accumulated lipids. Furthermore, we show that transfection of these cells with plasmids expressing human MTTP cDNA resulted in the expression of MTP protein, restoration of triglyceride transfer activity, and secretion of apoB100. Thus, these new cells can be valuable tools for studying structure-function of MTP, roles of different missense mutations in various lipid transfer activities of MTP and their ability to support apoB100 secretion, compensatory changes associated with loss of MTP, and in the identification of novel proteins that may require MTP for their synthesis and secretion.

Neuroendocrine prostate cancer (NEPC) is a lethal subtype of prostate cancer with limited meaningful treatment options. NEPC lesions uniquely express delta-like ligand 3 (DLL3) on their cell surface. Taking advantage of DLL3 overexpression, we developed and evaluated lutetium-177 (¹⁷⁷Lu)-labeled DLL3-targeting antibody SC16 (¹⁷⁷Lu-DTPA-SC16) as a treatment for NEPC. SC16 was functionalized with DTPA-CHX-A" chelator and radiolabeled with ¹⁷⁷Lu to produce ¹⁷⁷Lu-DTPA-SC16. Specificity and selectivity of ¹⁷⁷Lu-DTPA-SC16 were evaluated in vitro and in vivo using NCI-H660 (NEPC, DLL3-positive) and DU145 (adenocarcinoma, DLL3-negative) cells and xenografts. Dose-dependent treatment efficacy and specificity of ¹⁷⁷Lu-DTPA-SC16 radionuclide therapy were evaluated in H660 and DU145 xenograft-bearing mice. Safety of the agent was assessed by monitoring hematologic parameters. ¹⁷⁷Lu-DTPA-SC16 showed high tumor uptake and specificity in H660 xenografts, with minimal uptake in DU145 xenografts. At all three tested doses of ¹⁷⁷Lu-DTPA-SC16 (4.63, 9.25, and 27.75 MBq/mouse), complete responses were observed in H660-bearing mice; 9.25 and 27.75 MBq/mouse doses were curative. Even the lowest tested dose proved curative in five (63%) of eight mice, and recurring tumors could be successfully re-treated at the same dose to achieve complete responses. In DU145 xenografts, ¹⁷⁷Lu-DTPA-SC16 therapy did not inhibit tumor growth. Platelets and hematocrit transiently dropped, reaching nadir at 2 to 3 wk. This was out of range only in the highest-dose cohort and quickly recovered to normal range by week 4. Weight loss was observed only in the highest-dose cohort. Therefore, our data demonstrate that ¹⁷⁷Lu-DTPA-SC16 is a potent and safe radioimmunotherapeutic agent for testing in humans with NEPC.

Access to clinically relevant small cell lung cancer (SCLC) tissue is limited because surgical resection is rare in metastatic SCLC. Patient-derived xenografts (PDX) and circulating tumor cell-derived xenografts (CDX) have emerged as valuable tools to characterize SCLC. Here, we present a resource of 46 extensively annotated PDX/CDX models derived from 33 patients with SCLC. We perform multi-omic analyses, using targeted tumor next-generation sequencing, RNA-sequencing, and immunohistochemistry to deconvolute the mutational landscapes, global expression profiles, and molecular subtypes of these SCLC models. SCLC subtypes characterized by transcriptional regulators, ASCL1, NEUROD1 and POU2F3 are confirmed in this cohort. A subset of SCLC clinical specimens, including matched PDX/CDX and clinical specimen pairs, confirm that the primary features and genomic and proteomic landscapes of the tumors of origin are preserved in the derivative PDX models. This resource provides a powerful system to study SCLC biology.

PURPOSE/OBJECTIVE:Small cell lung cancer is an exceptionally lethal form of lung cancer with limited treatment options. Delta-like ligand 3 (DLL3) is an attractive therapeutic target as surface expression is almost exclusive to tumor cells. EXPERIMENTAL DESIGN/METHODS:Lu]Lu-DTPA-CHX-A"-SC16 binds to DLL3 on SCLC cells and delivers targeted radiotherapy while minimizing radiation to healthy tissue. RESULTS:Lu]Lu-DTPA-CHX-A"-SC16.

Small cell lung cancer (SCLC) is an aggressive malignancy characterized by early metastasis and extreme lethality. The backbone of SCLC treatment over the past several decades has been platinum-based doublet chemotherapy, with the recent addition of immunotherapy providing modest benefits in a subset of patients. However, nearly all patients treated with systemic therapy quickly develop resistant disease, and there is an absence of effective therapies for recurrent and progressive disease. Here we conducted CRISPR-Cas9 screens using a druggable genome library in multiple SCLC cell lines representing distinct molecular subtypes. This screen nominated exportin-1, encoded by XPO1, as a therapeutic target. XPO1 was highly and ubiquitously expressed in SCLC relative to other lung cancer histologies and other tumor types. XPO1 knockout enhanced chemosensitivity, and exportin-1 inhibition demonstrated synergy with both first- and second-line chemotherapy. The small molecule exportin-1 inhibitor selinexor in combination with cisplatin or irinotecan dramatically inhibited tumor growth in chemonaïve and chemorelapsed SCLC patient-derived xenografts, respectively. Together these data identify exportin-1 as a promising therapeutic target in SCLC with the potential to markedly augment the efficacy of cytotoxic agents commonly used in treating this disease.