Oxymestane, a cytostatic steroid derivative of exemestane with greater antitumor activity in non-estrogen-dependent cell lines

A new promising steroid derivative of Exemestane (Exe), the drug used for the treatment of estrogen-dependent breast cancer, was synthesized and evaluated against a set of human cancer cell lines. The new compound (Oxymestane-D1, Oxy) was tested comparatively with Exe against colon (C2BBe1, WiDr), liver (HepG2, HuH-7), lung (A549, H1299) and prostate (LNCaP, PC3) human cancer cell lines. Likewise, its effect on human colon normal cells (CCD-841 CoN) and human normal fibroblast cells (HFF-1) was studied. The cytostatic activity of Oxy was also compared with that of the reference cytostatic drugs used in chemotherapy protocols, namely carboplatin, cisplatin, doxorubicin, epirubicin, etoposide, flutamide, 5-fluorouracil, irinotecan, oxaliplatin and sorafenib. In all cell lines tested, Oxy proved to be more powerful cytostatic than Exe. Additionally, the IC₅₀ at 72 h showed a three-fold activity greater than 5-fluorouracil in the WiDr cell line, twice as high as cisplatin for cell line A549 and five times higher than cisplatin for cell line H1299. Also, Oxy surprisingly revealed to induce DNA damage and inhibit the DNA damage response (DDR) proteins ATM, ATR, CHK1 and CHK2. The results obtained allow concluding that Oxy can be a promising anticancer agent to be used in chemotherapy protocols. Furthermore, its ability to inhibit crucial components of DDR can also be useful for the monotherapy or for combination with chemo and/or radiotherapy of cancer.

Erectsterates A and B, a pair of novel highly degraded steroid derivatives from the South China Sea soft coral Sinularia erecta

Two novel steroidal derivatives, erectsterates A (1) and B (2), a pair of epimers at C-10, were isolated from the South China Sea soft coral Sinularia erecta. Their structures were established by extensive spectroscopic analysis and deduction from biosynthesis route. Compounds 1 and 2 are rare steroids with a highly degradation in ring B and an ester linkage between A and C/D rings, similar with the known compounds chaxines B (3) and D from an edible mushroom Agrocybe chaxingu. To the best of our knowledge, this is the first report of such kind of steroid from soft coral. And a different biosynthetic route from the reported approach of chaxines was proposed in this paper. Interestingly, the ring C of 1 and 2 was formally oxidized by Baeyer-Villiger reaction to provide an unprecedented seven-membered lactone moiety in ring C of steroid. The in vitro anti-proliferative activities of 2 were evaluated against A549, HT-29, SNU-398 and Capan-1 cell lines. The results indicated that it showed weak cytotoxicity against the tested four cell lines.