Abstract P2-11-26: The prognostic role of circulating tumor DNA after neoadjuvant chemotherapy in triple negative breast cancer with residual tumor

Background The presence of residual tumour at surgery (non-pathological complete response or non-pCR) occurs in about half of TNBCs treated with neoadjuvant chemotherapy (NAC) and signals chemoresistance and poor prognosis. Although further adjuvant chemotherapy (Capecitabine/Xeloda) results in improved survival in patients with non-pCR, only about 15% of such patients do benefit. Circulating tumor DNA (ctDNA) is a plasma-based biomarker that can be used to reveal real-time data about the disease and treatment progression. We have previously shown that detection of ctDNA after NAC signals poor prognosis. To validate and extend our previous results using an academic hospital-based tumor bespoke assay, we performed ctDNA measurements in non-pCR TNBC patients at the pre-operative, post-operative, 3 and 6-month time points. Methods Whole exome sequencing (WES) was performed on residual tumors from 34 TNBC patients to identify tumour-specific mutations (5/patient). Digital droplet PCR (ddPCR) assays were developed for these mutations and performed as per our previous work. Patients with at least one detectable mutation were considered ctDNA positive for a given time point. The detection of ctDNA was correlated with relapse-free survival (RFS). Results The overall RFS was 44%, with 56 % of patients received adjuvant Xeloda. Detection of ctDNA at the end of NAC (T1) correlated with poor prognosis of RFS (n = 33, p-value = 0.009, HR = 0.29 (95% CI = 0.12 to 0.74)). Detection of ctDNA after surgery (T2) and while on Xeloda (T3) showed no significant prognostic value for RFS. However, ctDNA detection at the 6-month time point, after Xeloda treatment (T4), showed stronger prognostic value for RFS (n = 17, p-value = 0.004, HR = 0.12 (95% CI = 0.03 to 0.51)). When measuring changes in ctDNA detectability from T1 to T4, 4 patients initially positive became ctDNA negative after the 6-month interval, and only 1 of these 4 had a relapse, compared with 10 of 11 that remained positive at the 6-month time point (p = 0.01, Chi-squared test). 3 of the 4 patients that cleared their ctDNA had received Xeloda. In addition, 2 patients initially negative became ctDNA positive at the 6-month time point (T4) and both relapsed, compared with only 1 of 5 that remained negative at 6 months (p = 0.035, Chi-squared test). For patients who received adjuvant Xeloda ctDNA positivity at T1 was associated with a worse RFS (p-value = 0.028, HR = 3.3884 (95% CI = 1.160 to 13.00)). Conclusion ctDNA testing using ddPCR in an academic hospital-based context at the post-NAC time point as well as at 6 months after surgery identifies an excellent prognostic group in TNBC patients with non-pCR and changes in ctDNA during the adjuvant period have prognostic value. This personalized approach to treatment management is ready for prospective testing in patients who have undergone NAC and require additional chemotherapy.

Citation Format: Talia Roseshter, Anna Klemantovich, Luca Cavallone, Adriana Aguilar-Mahecha, Josiane Lafleur, Oluwadara O. Elebute, Sarah Jenna, Jean-Francois Boileau, Manuela Pelmus, Mark Basik, Cathy Lan. The prognostic role of circulating tumor DNA after neoadjuvant chemotherapy in triple negative breast cancer with residual tumor [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P2-11-26.

A Day in the Life: Identification of Developmentally Regulated MicroRNAs in the Colorado Potato Beetle (Leptinotarsa decemlineata; Coleoptera: Chrysomelidae)

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is an important pest of the cultivated potato (Solanum tuberosum (L.) [Solanales: Solanaceae]). With its broad resistance toward commonly used insecticides, it is clear that more sophisticated control strategies are needed. Due to their importance in insect development, microRNAs (miRNAs) represent a potential tool to employ in insect control strategies. However, most studies conducted in this area have focused on model species with well-annotated genomes. In this study, next-generation sequencing was used to catalogue the miRNAs produced by L. decemlineata across all eight stages of its development, from eggs to adults. For most stages, the length of miRNAs peaked between 21 and 22 nt, though it was considerably longer for the egg stage (26 nt). Global profiling of miRNAs revealed three distinct developmental clusters: 1) egg stage; 2) early stage (first, second, and third instar); and 3) late stage (fourth instar, prepupae, pupae, and adult). We identified 86 conserved miRNAs and 33 bonafide novel miRNAs, including stage-specific miRNAs and those not previously identified in L. decemlineata. Most of the conserved miRNAs were found in multiple developmental stages, whereas the novel miRNAs were often stage specific with the bulk identified in the egg stage. The identified miRNAs have a myriad of putative functions, including growth, reproduction, and insecticide resistance. We discuss the putative roles of some of the most notable miRNAs in the regulation of L. decemlineata development, as well as the potential applications of this research in Colorado potato beetle management.

Transcriptional effects of polyethylene microplastics ingestion in developing zebrafish (Danio rerio)

Over the last few decades, plastic waste has become an increasing environmental concern as it accumulates in every environment on our planet. Though traditionally seen as a macroscopic problem (i.e., large plastic debris), plastic pollution is also evident at smaller scales. Indeed, the intentional industrial production of small plastic particles and the physical degradation of larger plastic debris have overtime resulted in an increased environmental prevalence of smaller plastic particles, including microplastics. While the effects of these small polymers on marine biota have been an important research focus, recent global surveys indicate that our freshwater lakes and rivers are also plagued by microplastics. However, despite these discoveries we currently have a limited understanding of the impact these particles may have on freshwater animals, particularly on vertebrate species. Thus, the aim of the present study was to assess the impact of high concentrations of microplastics (5 and 20 mg.L^-1) on the early life stages in zebrafish, a model freshwater vertebrate model. To do this, we exposed embryonic and larval zebrafish to fluorescently labelled polyethylene microspheres for up to 14 days and assessed their microplastic content, growth, hatching and oxygen consumption rates. We then explored the molecular underpinnings of the microplastic response by RNA sequencing. Over the course of the exposure, we observed a consistent accumulation of microplastics in the gastrointestinal tract of the fish in a concentration dependent manner, but could not detect any detrimental effects of these particles on larval development, growth or metabolism. However, whole animal transcriptomics revealed that microplastics induced a transient and extensive change in larval gene expression within 48 h exposure, which largely disappeared by 14 days. However, as these transcriptional changes occurred during a critical period of larval development, we suggest that an evaluation of the potential long-term impact of these particles is warranted.