Introduction: Once distantly metastasized, no curative treatment is currently available for penile cancer (PeCa). Treatment success is hampered by rapidly emerging chemotherapy resistance. At this stage, the disease is literally uncontrollable and extremely intrusive. Unfortunately, the precise resistance patterns and mechanisms are still unclear. We have recently provided evidence that state of resistance is characterized by upregulation of mTOR-AKT signaling pathway elements. In the current investigation, we investigated the impact of resistance to cisplatin and osimertinib on dissemination properties of penile cancer cells.
Methods: Therapy naïve cell line UKF-PeC3 and its respective resistant sublines to cisplatin (UKF-PeC3rCIS2) and osimertinib (UKF-PeC3rOSI2) were investigated. Motility, migration and invasion were assessed by modified Boyden chamber assay. Adhesion to vascular endothelium or immobilized collagen, fibronectin and laminin was quantified. Expression profiles of integrin receptors were assessed by flow cytometry. Functional value of selected integrin receptors has been investigated by blocking studies. Finally, effects of cell treatment with AKT-inhibitor capivasertib were determined.
Results: Motility, migration and invasion activity was significantly increased in resistant as compared to treatment-naïve cell lines. In contrast, treatment with cisplatin and osimertinib caused similar effects on adhesion to vascular endothelium and extracellular matrix proteins in treatment-naïve and resistant cell lines. Although resistant cell lines were characterized by distinct modulation of expression levels of integrin receptors a2, a6, ß1 and ß4, integrin blocking studies revealed no impact on their adhesion or motile behavior.
Upon capivasertib treatment, adhesion was significantly reduced in UKF-PeC3 and UKF-PeC3rCIS2. Furthermore, capivasertib significantly diminished viability in all PeCa cell lines. The IC50 value for capivasertib was significantly decreased in the UKF-PeC3rCIS2 (0.90 µM) and UKF-PeC3rOSI2 (0.87 µM) in comparison to treatment-naive cells UKF-PeC3 (10.61 µM), thus, demonstrating a stronger inhibiting effect in resistant cell lines.
Conclusions: In the current study, we showed a more invasive dissemination behavior of PeCa cells in state of resistance and the auspicious role of the mTOR/AKT signaling pathway for therapeutic use. In the regard of the stronger inhibiting effect of the AKT inhibitor capivasertib on viability of resistant than of treatment-naïve cells, its potential role as a second-line treatment option in future trials merits to be taken into account.
Source of Funding: Brigitte und Dr. Konstanze Wegener Foundation
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