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Variant allele frequency enrichment analysis in vitro reveals sonic hedgehog pathway to impede sustained temozolomide response in GBM.

Biswas NK, Chandra V, Sarkar-Roy N, Das T, Bhattacharya RN, Tripathy LN, Basu SK, Kumar S, Das S, Chatterjee A, Mukherjee A, Basu P, Maitra A, Chattopadhyay A, Basu A, Dhara S - Sci Rep (2015)

Bottom Line: Enrichment of VAFs was found on genes ST5, RP6KA1 and PRKDC in cells showing sustained TMZ-effect whereas on genes FREM2, AASDH and STK36, in cells showing reversible TMZ-effect.Ingenuity pathway analysis (IPA) revealed that these genes alter cell-cycle, G2/M-checkpoint-regulation and NHEJ pathways in sustained TMZ-effect cells whereas the lysine-II&V/phenylalanine degradation and sonic hedgehog (Hh) pathways in reversible TMZ-effect cells.Altogether, our results indicate that the Hh-pathway impedes sustained TMZ-response in GBM and could be a potential therapeutic target to enhance TMZ-response in this malignancy.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Biomedical Genomics, Kalyani, West Bengal 741251, India.

ABSTRACT
Neoplastic cells of Glioblastoma multiforme (GBM) may or may not show sustained response to temozolomide (TMZ) chemotherapy. We hypothesize that TMZ chemotherapy response in GBM is predetermined in its neoplastic clones via a specific set of mutations that alter relevant pathways. We describe exome-wide enrichment of variant allele frequencies (VAFs) in neurospheres displaying contrasting phenotypes of sustained versus reversible TMZ-responses in vitro. Enrichment of VAFs was found on genes ST5, RP6KA1 and PRKDC in cells showing sustained TMZ-effect whereas on genes FREM2, AASDH and STK36, in cells showing reversible TMZ-effect. Ingenuity pathway analysis (IPA) revealed that these genes alter cell-cycle, G2/M-checkpoint-regulation and NHEJ pathways in sustained TMZ-effect cells whereas the lysine-II&V/phenylalanine degradation and sonic hedgehog (Hh) pathways in reversible TMZ-effect cells. Next, we validated the likely involvement of the Hh-pathway in TMZ-response on additional GBM neurospheres as well as on GBM patients, by extracting RNA-sequencing-based gene expression data from the TCGA-GBM database. Finally, we demonstrated TMZ-sensitization of a TMZ non-responder neurosphere in vitro by treating them with the FDA-approved pharmacological Hh-pathway inhibitor vismodegib. Altogether, our results indicate that the Hh-pathway impedes sustained TMZ-response in GBM and could be a potential therapeutic target to enhance TMZ-response in this malignancy.

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Related in: MedlinePlus

(A) Schematic diagram of a model to explain TMZ-response in GBM neoplastic cells on the perspective of clonal heterogeneity. (B) The experimental design for TMZ-treatment and post-treatment recovery of GBM neurospheres in vitro to address this hypothetical model of TMZ-response.
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f1: (A) Schematic diagram of a model to explain TMZ-response in GBM neoplastic cells on the perspective of clonal heterogeneity. (B) The experimental design for TMZ-treatment and post-treatment recovery of GBM neurospheres in vitro to address this hypothetical model of TMZ-response.

Mentions: When GBM neoplastic cells are exposed to the chemotherapeutic drug TMZ, the first theoretical possibility (possibility # 1 in Fig. 1A) is that all cells undergo apoptosis and die, leaving no residual cells. Another extreme is possibility # 5 (Fig. 1A), nothing happens to the cells and they keep cycling. The other possibilities are partial apoptosis (possibilities #2, #3 and #4 in Fig. 1A). Under these conditions, the residual cells following drug withdrawal may either show cell-cycle arrest (possibilities #2 and #3) or they may keep cycling (possibility #4). The cells which initially show cell-cycle arrest may either undergo a terminal differentiation by inducing cellular senescence resulting sustained response after the drug withdrawal (possibility #2) or may show reversible drug-effect by going back to the cell-cycle again (possibility #3). We provide evidence for possibilities #2 and #3 as a result of two GBM patient-derived neurospheres which repeatedly showed sustained versus reversible response to TMZ-treatment in vitro, irrespective of their cellular passages. Our experimental design of TMZ-treatment and post-treatment recovery (Fig 1B) was modified from Mihaliak et al,14.


Variant allele frequency enrichment analysis in vitro reveals sonic hedgehog pathway to impede sustained temozolomide response in GBM.

Biswas NK, Chandra V, Sarkar-Roy N, Das T, Bhattacharya RN, Tripathy LN, Basu SK, Kumar S, Das S, Chatterjee A, Mukherjee A, Basu P, Maitra A, Chattopadhyay A, Basu A, Dhara S - Sci Rep (2015)

(A) Schematic diagram of a model to explain TMZ-response in GBM neoplastic cells on the perspective of clonal heterogeneity. (B) The experimental design for TMZ-treatment and post-treatment recovery of GBM neurospheres in vitro to address this hypothetical model of TMZ-response.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4300501&req=5

f1: (A) Schematic diagram of a model to explain TMZ-response in GBM neoplastic cells on the perspective of clonal heterogeneity. (B) The experimental design for TMZ-treatment and post-treatment recovery of GBM neurospheres in vitro to address this hypothetical model of TMZ-response.
Mentions: When GBM neoplastic cells are exposed to the chemotherapeutic drug TMZ, the first theoretical possibility (possibility # 1 in Fig. 1A) is that all cells undergo apoptosis and die, leaving no residual cells. Another extreme is possibility # 5 (Fig. 1A), nothing happens to the cells and they keep cycling. The other possibilities are partial apoptosis (possibilities #2, #3 and #4 in Fig. 1A). Under these conditions, the residual cells following drug withdrawal may either show cell-cycle arrest (possibilities #2 and #3) or they may keep cycling (possibility #4). The cells which initially show cell-cycle arrest may either undergo a terminal differentiation by inducing cellular senescence resulting sustained response after the drug withdrawal (possibility #2) or may show reversible drug-effect by going back to the cell-cycle again (possibility #3). We provide evidence for possibilities #2 and #3 as a result of two GBM patient-derived neurospheres which repeatedly showed sustained versus reversible response to TMZ-treatment in vitro, irrespective of their cellular passages. Our experimental design of TMZ-treatment and post-treatment recovery (Fig 1B) was modified from Mihaliak et al,14.

Bottom Line: Enrichment of VAFs was found on genes ST5, RP6KA1 and PRKDC in cells showing sustained TMZ-effect whereas on genes FREM2, AASDH and STK36, in cells showing reversible TMZ-effect.Ingenuity pathway analysis (IPA) revealed that these genes alter cell-cycle, G2/M-checkpoint-regulation and NHEJ pathways in sustained TMZ-effect cells whereas the lysine-II&V/phenylalanine degradation and sonic hedgehog (Hh) pathways in reversible TMZ-effect cells.Altogether, our results indicate that the Hh-pathway impedes sustained TMZ-response in GBM and could be a potential therapeutic target to enhance TMZ-response in this malignancy.

View Article: PubMed Central - PubMed

Affiliation: National Institute of Biomedical Genomics, Kalyani, West Bengal 741251, India.

ABSTRACT
Neoplastic cells of Glioblastoma multiforme (GBM) may or may not show sustained response to temozolomide (TMZ) chemotherapy. We hypothesize that TMZ chemotherapy response in GBM is predetermined in its neoplastic clones via a specific set of mutations that alter relevant pathways. We describe exome-wide enrichment of variant allele frequencies (VAFs) in neurospheres displaying contrasting phenotypes of sustained versus reversible TMZ-responses in vitro. Enrichment of VAFs was found on genes ST5, RP6KA1 and PRKDC in cells showing sustained TMZ-effect whereas on genes FREM2, AASDH and STK36, in cells showing reversible TMZ-effect. Ingenuity pathway analysis (IPA) revealed that these genes alter cell-cycle, G2/M-checkpoint-regulation and NHEJ pathways in sustained TMZ-effect cells whereas the lysine-II&V/phenylalanine degradation and sonic hedgehog (Hh) pathways in reversible TMZ-effect cells. Next, we validated the likely involvement of the Hh-pathway in TMZ-response on additional GBM neurospheres as well as on GBM patients, by extracting RNA-sequencing-based gene expression data from the TCGA-GBM database. Finally, we demonstrated TMZ-sensitization of a TMZ non-responder neurosphere in vitro by treating them with the FDA-approved pharmacological Hh-pathway inhibitor vismodegib. Altogether, our results indicate that the Hh-pathway impedes sustained TMZ-response in GBM and could be a potential therapeutic target to enhance TMZ-response in this malignancy.

Show MeSH
Related in: MedlinePlus