Sentence: Liposomes were surface modified with transferrin ( Tf ) for receptor targeting , and cell penetrating peptide PFVYLI ( PFV ) to increase translocation of doxorubicin ( Dox ) and Erlotinib ( Erlo ) across the BBB into glioblastoma ( U87 ) tumor cells .
Drug combination annotation:
[{'class': 'POS', 'spans': ['doxorubicin', 'Erlotinib'], 'is_context_needed': True}]