Enhanced inhibition of clonogenic survival of human medulloblastoma cells by multimodal treatment with ionizing irradiation, epigenetic modifiers, and differentiation-inducing drugs.
Medulloblastoma (MB) is the most common pediatric brain tumor. Current treatment regimes consisting of primary surgery followed by radio- and chemotherapy, achieve 5-year overall survival rates of only about 60 %. Therapy-induced endocrine and neurocognitive deficits are common late adverse effects. Thus, improved antitumor strategies are urgently needed. In this study, we combined irradiation (IR) together with epigenetic modifiers and differentiation inducers in a multimodal approach to enhance the efficiency of tumor therapy in MB and also assessed possible late adverse effects on neurogenesis.



In three human MB cell lines (DAOY, MEB-Med8a, D283-Med) short-time survival (trypan blue exclusion assay), apoptosis, autophagy, cell cycle distribution, formation of gH2AX foci, and long-term reproductive survival (clonogenic assay) were analyzed after treatment with 5-aza-2'-deoxycytidine (5-azadC), valproic acid (VPA), suberanilohydroxamic acid (SAHA), abacavir (ABC), all-trans retinoic acid (ATRA) and resveratrol (RES) alone or combined with 5-aza-dC and/or IR. Effects of combinatorial treatments on neurogenesis were evaluated in cultured murine hippocampal slices from transgenic nestin-CFPnuc C57BL/J6 mice. Life imaging of nestin-positive neural stem cells was conducted at distinct time points for up to 28 days after treatment start.



All tested drugs showed a radiosynergistic action on overall clonogenic survival at least in two-outof-three MB cell lines. This effect was pronounced in multimodal treatments combining IR, 5-aza-dC and a second drug. Hereby, ABC and RES induced the strongest reduction of clongenic survival in all three MB cell lines and led to the induction of apoptosis (RES, ABC) and/or autophagy (ABC). Additionally, 5-aza-dC, RES, and ABC increased the S phase cell fraction and induced the formation of gH2AX foci at least in oneout-of-three cell lines. Thereby, the multimodal treatment with 5-aza-dC, IR, and RES or ABC did not change the number of normal neural progenitor cells in murine slice cultures.



In conclusion, the radiosensitizing capacities of epigenetic and differentiation-inducing drugs presented here suggest that their adjuvant administration might improve MB therapy. Thereby, the combination of 5-aza-dC/IR with ABC and RES seemed to be the most promising to enhance tumor control without affecting the normal neural precursor cells.
Department of Radiation Therapy, University of Leipzig, Stephanstraße 9a, Leipzig, 04103, Germany. Ina.patties@medizin.uni-leipzig.de.
Ina
I
Patties
Department of Radiation Therapy, University of Leipzig, Stephanstraße 9a, Leipzig, 04103, Germany.
Rolf-Dieter
RD
Kortmann
Institute of Anatomy, University of Leipzig, Liebigstraße 13, 04103, Leipzig, Germany.
Franziska
F
Menzel
Department of Radiation Therapy, University of Leipzig, Stephanstraße 9a, Leipzig, 04103, Germany.
Annegret
A
Glasow
D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000008:administration & dosage / Q000494:pharmacology; D001374:Azacitidine / Q000008:administration & dosage / Q000031:analogs & derivatives / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000528:radiation effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects / Q000528:radiation effects; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D002528:Cerebellar Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000532:radiotherapy*; D003131:Combined Modality Therapy; D000077209:Decitabine; D015224:Dideoxynucleosides / Q000008:administration & dosage / Q000494:pharmacology; D044127:Epigenesis, Genetic / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D006877:Hydroxamic Acids / Q000008:administration & dosage / Q000494:pharmacology; D008527:Medulloblastoma / Q000188:drug therapy* / Q000235:genetics / Q000532:radiotherapy*; D051379:Mice; D055495:Neurogenesis / Q000187:drug effects / Q000528:radiation effects; D011838:Radiation-Sensitizing Agents / Q000008:administration & dosage* / Q000494:pharmacology; D000077185:Resveratrol; D013267:Stilbenes / Q000008:administration & dosage / Q000494:pharmacology; D016896:Treatment Outcome; D014212:Tretinoin / Q000008:administration & dosage / Q000494:pharmacology; D014635:Valproic Acid / Q000008:administration & dosage / Q000494:pharmacology; D000077337:Vorinostat; D023041:Xenograft Model Antitumor Assays; D000099227:Abacavir
D000970:Antineoplastic Agents; D001374:Azacitidine; D000077209:Decitabine; D015224:Dideoxynucleosides; D006877:Hydroxamic Acids; D011838:Radiation-Sensitizing Agents; D000077185:Resveratrol; D013267:Stilbenes; D014212:Tretinoin; D014635:Valproic Acid; D000077337:Vorinostat; D000099227:Abacavir