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Tumor shedding and metastatic progression after tumor excision in patient-derived orthotopic xenograft models of triple-negative breast cancer.

ABSTRACT: Patient-derived orthotopic xenograft (PDOX) models have been verified as a useful method for studying human cancers in mice. Previous studies on the extent of metastases in these models have been limited by the necessity of welfare euthanasia (primary tumors reaching threshold size), at which point metastases may only be micrometers in diameter, few in number, and solely identified by step-sectioning of formalin-fixed paraffin-embedded tissue. These small micro-metastases are less suitable for many downstream molecular analyses than macro-metastases. Resection of the primary tumor by survival surgery has been proven to allow further time for metastases to grow. Although PDOX models of triple-negative breast cancer (TNBC) shed circulating tumor cells (CTCs) into the bloodstream and metastasize, similar to human TNBC, little data has been collected in these TNBC PDOX models regarding the association between CTC characteristics and distant metastasis following excision of the primary tumor xenograft. This study assembles a timeline of PDOX tumor shedding and metastatic tumor progression before and after tumor excision surgery. We report the ability to use tumorectomies to increase the lifespan of TNBC PDOX models with the potential to obtain larger metastases. CTC clusters and CTCs expressing a mesenchymal marker (vimentin) were associated with metastatic burden in lung and liver. The data collected through these experiments will guide the further use of PDOX models in studying metastatic TNBC.

SUBMITTER: Razmara AM

PROVIDER: S-EPMC8723898 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer, with approximately 50% of patients having residual disease after neoadjuvant chemotherapy (NACT) and worse prognosis with higher residual cancer burden (RCB). Patient-derived xenograft (PDX) models of breast cancer are an effective discovery platform and tool for preclinical pharmacologic testing and biomarker identification. There is a need for PDX models encompassing the heterogeneity of TNBC both pre- and post- therapy and for identifying clinical and molecular features of patient’s tumors that are associated with success in establishing these models. Using fine-needle aspirates (FNAs), we established orthotopic PDX models of TNBC from the primary breast tumors of patients prior to and following neoadjuvant systemic therapy while enrolled in the ARTEMIS trial (NCT02276443). ARTEMIS is a prospective neoadjuvant clinical trial for women with primary TNBC who are treated with four cycles of Adriamycin combined with cyclophosphamide (AC) followed by taxane +/- different experimental therapies. Serial biopsies were obtained from patients prior to treatment (pre-therapy), from poorly responsive disease after four cycles of AC (mid-NACT), and in cases of AC-resistance, after a three-month course of different experimental therapies and/or additional chemotherapy (post-NACT). Our study cohort includes a total of 269 FNA biopsies from 217 women, generating a total of 62 successful PDX models (overall success-rate = 23%). This cohort includes five serial pre- and mid-NACT PDX pairs, as well as one serial pre-, mid-, post-NACT triplet. Success of PDX engraftment was generally higher from cancers that proved to be treatment-resistant: whether poor response to AC determined by ultrasound measurements mid-NACT (p=0.063), RCB II/III status after NACT (p=0.046), or metastatic relapse within two years of surgery (p=0.008). TNBC molecular subtype determined from gene expression microarrays of pre-NACT tumor revealed no significant association with PDX engraftment rate (p=0.877). Finally, we developed a statistical model predictive of PDX engraftment using percent Ki67 positive cells in the patient’s diagnostic biopsy, positive lymph node status at diagnosis, and low volumetric reduction of the patient’s tumor following AC treatment. This novel bank of 62 PDX models of TNBC provides a valuable resource for biomarker discovery and preclinical therapeutic trials aimed at improving neoadjuvant response rates for patients with TNBC.

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Tumor shedding and metastatic progression after tumor excision in patient-derived orthotopic xenograft models of triple-negative breast cancer.

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