Drug resistance in luminal breast tumors: Results of a novel in vitro breast cancer chemoresistance platform

Authors

  • Martina Lichtenfels Ziel Biosciences – Porto Alegre (RS), Brazil.
  • Caio Caloca Severo Serviço de Mastologia, Grupo Hospitalar Conceição – Porto Alegre (RS), Brazil.
  • Marco Aurélio Veiga Conrado Serviço de Mastologia, Grupo Hospitalar Conceição – Porto Alegre (RS), Brazil.
  • Isis Mendes Barbosa Serviço de Mastologia, Grupo Hospitalar Conceição – Porto Alegre (RS), Brazil.
  • Camila Alves da Silva Ziel Biosciences – Porto Alegre (RS), Brazil.
  • Júlia Caroline Marcolin Ziel Biosciences – Porto Alegre (RS), Brazil.
  • Caroline Brunetto de Farias Ziel Biosciences – Porto Alegre (RS), Brazil.
  • José Luiz Pedrini Serviço de Mastologia, Grupo Hospitalar Conceição – Porto Alegre (RS), Brazil.

DOI:

https://doi.org/10.29289/259453942023V33S1016

Keywords:

breast neoplasms, drug therapy, taxanes, anthracyclines, drug resistance

Abstract

Objective: The aim of our preliminary study was to validate a novel in vitro chemoresistance platform to predict the
response of luminal tumors to cytotoxic drugs commonly used in neoadjuvant settings. Methodology: Patients with
estrogen receptor (ER)-positive breast cancer tumors who underwent upfront surgery were included. Fresh tumor samples
were collected during surgery and dissociated to obtain the tumor cells. The tumor cells were cultured in the chemoresistance platform with anthracyclines and taxanes, and after 72 h, cell viability was evaluated. The test result is defined
based on cell viability as low (<40%), medium (40%–60%), and high (>60%) resistance. One BC cell line (MCF-7 (luminal))
was used to confirm the response to the drugs. Results: Samples from 13 patients diagnosed with ER+/HER positive and/
or negative undergoing upfront surgery were tested in the chemoresistance platform. Nine (69.2%) patients presented
luminal A tumors, 2 (15.4%) luminal B, and 2 (15.4%) luminal B/HER2. The chemoresistance platform demonstrated that
samples presented higher resistance to taxanes compared with anthracyclines. In taxanes, 75% presented high resistance
to docetaxel and 61.6% to paclitaxel, and in anthracyclines, only 15%, and 8.3% presented high resistance to doxorubicin and epirubicin, respectively. To confirm these differences in drug response, we evaluated the cell survival rate of an
ER-positive cell lineage (MCF-7) after the treatment with the same drugs using the IC50 (50% inhibitory concentration).
In accordance with our previous results, we observed lower rates of high resistance to doxorubicin (34%) and epirubicin
(37%) and higher rates using paclitaxel (58%) and docetaxel (67%). Conclusion: This preliminary finding highlighted the
technique success of the in vitro chemoresistance platform and suggested a possible role of intrinsic resistance in the
worse response to neochemotherapy of patients with luminal tumors.

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Published

2026-03-12

How to Cite

Lichtenfels, M., Severo, C. C., Conrado, M. A. V., Barbosa, I. M., Silva, C. A. da, Marcolin, J. C., … Pedrini, J. L. (2026). Drug resistance in luminal breast tumors: Results of a novel in vitro breast cancer chemoresistance platform. Mastology, 33(suppl.1). https://doi.org/10.29289/259453942023V33S1016

Issue

Vol. 33 No. suppl.1 (2023)

Section

Oral Presentation

License

Copyright (c) 2026 Martina Lichtenfels, Caio Caloca Severo, Marco Aurélio Veiga Conrado, Isis Mendes Barbosa, Camila Alves da Silva, Júlia Caroline Marcolin, Caroline Brunetto de Farias, José Luiz Pedrini

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.