gms | German Medical Science

Objective: Cerebral metastases are common intracranial lesions and have enormous prognostic impact. In many cases, brain metastases seem to be insensitive to chemotherapeutic treatment and are often source of recurrence. To date, the reasons for this are not entirely known. Dormant tumor cells are a population of non-apoptotic, low proliferating cells, which have the ability to be reactivated and can be the source of recurrence. Another mechanism of tumor cell survival are immunological escape mechanisms, involving the Natural Killer Group 2, member D (nkg2d) receptor-ligand system. In a previous study we were able to show that human brain metastases of pulmonary and breast cancer harbor a significant amount of dormant tumor cells, which often coexpress NKG2D ligands. We now wanted to investigate, whether chemotherapeutic treatment has an effect on expression of dormancy markers and nkg2d ligands.

Methods: The murine breast cancer cell line E0771 and the murine pulmonary cancer cell line LLC were treated with ascending doses of cisplatin and cyclophosphamid, which are also used in humans, for 10 days in comparison to respective negative controls. Expression of the dormancy-associated markers pdgf, fgf2, hif1alpha, epha5, h2bk and igfbp5 and the nkg2d ligands mult1, h60a, h60b, h60c and reat1b were analyzed be qrtPCR and immunocytochemnistry (IHC).

Results: Whereas cyclophosphamide had no effect on dormancy marker and nkg2dl expression, treatment with cisplatin led to an upregulation of nkg2dl and dormancy markers in LLC and E0771 in a dose dependent manner: A concentration of 1µM led to an induction of mult1, raet1b, h2bk and fgf2 in LLC and mult1 and fgf2 in E0771, a concentration of 3 µM led to an induction of mult1, h2bk and fgf2 in LLC and mult1 and raet1b in E0771 and a concentration of 5 µM to induction of mult1, raet1b, h2bk, hif1alpha and fgf2 in E0771.

Conclusion: Although chemotherapy with cisplatin leads to death of many cells in culture, the surviving cells show a high expression of dormancy markers and of certain nkg2d ligands. Not only acquisition of dormancy but also nkg2d ligand expression might play an important role in chemoresistance of brain metastases.