Prospective neoadjuvant analysis of PET imaging and mechanisms of resistance to Trastuzumab shows role of HIF1 and autophagy.
BACKGROUND
Although Trastuzumab has improved survival of HER2+ breast cancer patients, resistance to the agent pre-exists or develops through the course of therapy. Here we show that a specific metabolism and autophagy-related cancer cell phenotype relates to resistance of HER2+ breast cancer to Trastuzumab and chemotherapy.


METHODS
Twenty-eight patients with locally advanced primary breast cancer were prospectively scheduled to received one cycle of Trastuzumab followed by a new biopsy on day 21, followed by taxol/Trastuzumab chemotherapy for four cycles before surgery. FDG PET/CT scan was used to monitor tumour response. Tissue samples were immunohistochemically analysed for metabolism and autophagy markers.


RESULTS
In pre-Trastuzumab biopsies, the LC3A+/HER2+ cell population was correlated with HIF1α expression (P=0.01), while GLUT1 and LC3B expression were correlated with Ki67 proliferation index (P=0.01 and P=0.01, respectively). FDG PET tumour dimensions before therapy were correlated with LC3B expression (P=0.005). Administration of Trastuzumab significantly reduced clinical and PET-detected tumour dimensions (P<0.01). An inverse association of tumour response with the percentage of cells expressing HIF1α at baseline was documented (P=0.01). Administration of Trastuzumab resulted in a decrease of the proliferation index (P=0.004), GLUT1 (P=0.04) and HER2 (P=0.01) expression. In contrast, the percentage of LC3A+/HER2+ cells was increased (P=0.01). High baseline HIF1α expression was the only parameter associated with poorer pathological response to preoperative chemotherapy (P=0.001).


CONCLUSIONS
As the HER2+/LC3A+ phenotype, which often overexpresses HIF1α, is a major subpopulation increasing after therapy with Trastuzumab, LC3A- and HIF1α-targeting therapies should be investigated for the augmentation of anti-HER2 therapy efficacy.
Department of Radiotherapy/Oncology, University Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece.
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Koukourakis
Department of Pathology, University Hospital of Alexandroupolis, Democritus University of Thrace, Alexandroupolis, Greece.
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Giatromanolaki
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Bottini
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Cappelletti
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Zanotti
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Allevi
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Strina
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Ardine
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Milani
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Brugnoli
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Martinotti
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Ferrero
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Bertoni
UO Radiologia, Ospedale San Camillo, Cremona, Italy.
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Ferrozzi
Cancer Research UK, Molecular Oncology Laboratories, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, UK.
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Harris
UO Multidisciplinare di Patologia Mammaria, US Terapia Molecolare e Farmacogenomica, UOÂ Anatomia Patologica, Istituti Ospitalieri di Cremona, Cremona, Italy.
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Generali
D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage / Q000627:therapeutic use*; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001343:Autophagy; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000188:drug therapy* / Q000473:pathology; D019008:Drug Resistance, Neoplasm; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000502:physiology*; D008869:Microtubule-Associated Proteins; D020360:Neoadjuvant Therapy; D049268:Positron-Emission Tomography; D011446:Prospective Studies; D012189:Retrospective Studies; D000068878:Trastuzumab
D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; C477012:MAP1LC3A protein, human; C502070:MAP1LC3B protein, human; D008869:Microtubule-Associated Proteins; D019788:Fluorodeoxyglucose F18; D000068878:Trastuzumab