The natural compound trabectedin (Ecteinascidin 743, Yondelis®)
represents an alkylating tetrahydroisoquinoline alkaloid
initially isolated from the tunicate Ecteinascidia turbinata of the
Caribbean Sea, which is the host of the trabectedin-forming bacterial
symbiont Endoecteinascidia frumentensis (Fig. 4) [76]. Trabectedin
exhibited strong cytotoxic activity against various tumors
and was approved for the therapy of soft tissue sarcoma and
ovarian cancer [76]. Trabectedin damages DNA by a unique mechanism,
the trabectedin molecule binds to nitrogen-N2 of guanine
bases of the DNA minor groove which causes a bended DNA
molecule followed by interaction with DNA binding proteins of the
TC-NER (transcription-coupled nucleotide excision repair) DNArepair
system leading to cell death in the end via formation of
double strand breaks in particular in HR(homologous
recombination)-deficient cells [76]. In addition, trabectedin
inhibited the transcription activity of FUS-CHOP in sensitive myxoid
liposarcoma (MLS) [77]. Facing the influence of trabectedin on
transcription, D'Incalci and coworkers investigated the effects of
trabectedin on miRNA expression in MLS cells (402-91 sensitive
and 402-91/ET trabectedin-resistant MLS cells) [78]. In the
trabectedin-resistant cells, the tumor suppressor let-7e was suppressed
(three-fold) and oncogenic miR-21 was upregulated (twofold)
when compared with the sensitive MLS cells which was
consequently accompanied by the upregulation of let-7e targets
(CCDN1, SEMA4C, E2F5) and suppression of miR-21 targets (PDCD4)
in the resistant cells [78]. In addition, the tumor suppressors miR-
192, miR-130a and miR-98 were downregulated in 402-91/ET