The Therapeutic Potential of Migrastatin-Core Analogs for the Treatment of Metastatic Cancer

Abstract

Tumor metastasis is a complex process in which cells detach from the primary tumor and colonize a distant organ. Metastasis is also the main process responsible for cancer-related death. Despite the enormous efforts made to unravel the metastatic process, there is no effective therapy, and patients with metastatic tumors have poor prognosis. In this regard, there is an urgent need for new therapeutic tools for the treatment of this disease. Small molecules with the capacity to reduce cell migration could be used to treat metastasis. Migrastatin-core analogs are naturally inspired macrocycles that inhibit pathological cell migration and are able to reduce metastasis in animal models. Migrastatin analogs can be synthesized from a common advanced intermediate. Herein we present a review of the synthetic approaches that can be used to prepare this key intermediate, together with a review of the biological activity of migrastatin-core analogs and current hypotheses concerning their mechanism of action.

Keywords: cancer metastasis; diverted total synthesis; natural products.

Figure 1

Small-molecule inhibitors of cell mobility.

Figure 2

Diverted total synthesis approach for the preparation of migrastatin (7) and truncated analogs MGSTA-1,6 from a common advanced intermediate (8). IC₅₀ values (in parentheses) in boyden chamber assays against ^a 4T1 mouse mammary cancer and ^b A549 human lung cancer cells.

Figure 3

Synthetic strategies for the preparation of advanced intermediate 8.

Scheme 1

Danishefsky’s synthesis of protected MGSTA-1 (19). Reagents and conditions: (a) TBDPSCl, imidazole, DMF; (b) MeI, NaH, THF; (c) H₂, Pd(OH)₂, EtOAc, 73% over three steps; (d) (COCl)₂, Et₃N, DMSO, CH₂Cl₂; (e) TiCl₄, CH₂Cl₂; (f) CSA, PhMe, 71% over three steps; (g) NaBH₄, EtOH, CeCl₃·7H₂O; (h) CSA, H₂O, THF; (i) LiBH₄, H₂O, THF, 55% over three steps; (j) (E)-hepta-2,6-dienoyl chloride, DMAP, CH₂Cl₂, 65%; (k) MOMCl, Bu₄NI, DIPEA, CH₂Cl₂; (l) HF.py, THF, 79% over two steps; (m) DMP, CH₂Cl₂; (n) Tebbe reagent, pyridine, THF, 60% over two steps; (o) Grubbs II catalyst, PhCH₃, reflux, 50%.

Scheme 2

Danishefsky’s synthesis of 8. Reagents and conditions: (a) DIBALH, then ZnCl₂, H₂C=CHMgBr, PhCH₃, −78 °C to RT, 75% (ds > 90%); (b) (i) MeI, NaH, DMF, RT, (ii) 2 M HCl, MeOH, reflux, 80%; (c) Pb(OAc)₄, Na₂CO₃, CH₂Cl₂, 0 °C to RT; (d) (i) TiCl₄, CH₂Cl₂, −78 °C, (ii) TFA, CH₂Cl₂, RT, 87% from 22; (e) LiBH₄, MeOH, THF, −10 °C; (f) CSA, H₂O, THF, reflux; (g) LiBH₄, H₂O, THF, RT, 53% from 24; (h) TBSOTf, 2,6-lutidine, CH₂Cl₂, RT, (ii) AcOH:H₂O:THF (3:1:1), RT, 80%.

Scheme 3

Danishefsky’s synthesis of the migrastatin-core library. Reagents and conditions: (a) (E)-hepta-2,6-dienoic acid, 2,4,6-trichlorobenzoyl chloride, DIPEA, pyridine, PhCH₃, RT, 48%; (b) Grubbs II catalyst (20 mol %), PhCH₃ (0.5 mM), reflux, 55% (28), 76% (30), 81% (34), 60% (37); (c) HF^.pyridine, THF, RT, 66% (MGSTA-1), 94% (MGSTA-2), 90% (MGSTA-3), 81% (MGSTA-4); (d) 6-heptenoyl chloride, DMAP, CH₂Cl₂, RT, 82%; (e) CBr₄, solid-supported PPh₃, CH₂Cl₂, RT; (f) (i) β-ketosulfone 32, DBU, PhCH₃, RT, (ii) Na/Hg, Na₂HPO₄, MeOH, RT, 61% from 7; (g) DPPA, DBU, PhCH₃, RT, 87%; (h) (i) PPh₃, H₂O, THF, 70 °C, (ii) 6-heptenoic acid, EDC, DIPEA, CH₂Cl₂, RT, 92%.

Scheme 4

Cossy’s synthesis of 46. Reagents and conditions: (a) pTSA, MeOH/H₂O (1:1), RT, 83%; (b) TBDPSCl, imidazole, CH₂Cl₂, 0 °C to RT 81%; (c) Ag₂O, MeI, MS 4 Å, Et₂O, 40 °C, 96%; (d) DIBAL, CH₂Cl₂, −78 °C to RT 90%; (e) (COCl)₂, DMSO, CH₂Cl₂, −78 °C, then Et₃N −78 °C to RT; (f) MgBr₂·OEt₂, CH₂Cl₂, −20 °C, then but-2-enyl-[(tri(n-butyl)]stannane, −60 °C, 87% (over two steps); (g) methacryloyl chloride, Et₃N, DMAP, CH₂Cl₂, 0 °C to RT 80%; (h) Grubbs II catalyst (16.5 mol %), CH₂Cl₂ (c = 10⁻² M), 40 °C, 144 h, 65%; (i) LiBH₄ (7 equiv.), CeCl₃·7H₂O (1 equiv.), THF/H₂O (4:1), RT, 74%; (j) TBSOTf, 2,6-lutidine, CH₂Cl₂, 0 °C to RT, 75%; (k) THF/H₂O/AcOH (1:1:3), 36 h, RT, 75%.

Scheme 5

Synthesis of MGSTA-1. Reagents and conditions: (a) TBSOTf, 2,6-lutidine, CH₂Cl₂, −20 °C, 93%; (b) (i) OsO₄, NMO, t-BuOH/H₂O (1/1), RT; (ii) NaIO₄, THF/H₂O (1/1), RT; (iii) 47, KHMDS, 18-crown-6, THF, −78 °C, 80% (over 3 steps); (c) DIBAL, CH₂Cl₂, −78 °C to RT, 94%; (d) (E)-2,4,6-trichlorobenzoic (E)-hepta-2,6-dienoic anhydride, Pyridine, PhCH₃, RT, 67%; (e) NH₄F MeOH, reflux, 77%; (f) Dess-Martin Periodinane CH₂Cl₂, 0 °C to RT; (g) Zn, PbCl₂ cat, CH₂I₂Ti(Oi-Pr)₄, THF, RT (h) Grubbs II catalyst (20 mol %), PhCH₃, reflux, 47%; (i) HF Py, THF, RT, 67%.

Scheme 6

Iqbal’s synthesis of 65. Reagents and conditions: (a) n-Bu₂BOTf, i-Pr₂NEt, CH₂Cl₂, −78 °C to 0 °C, 1 h, 84%; (b) LiBH₄, MeOH, THF, 0 °C, 2 h, 96%; (c) (OMe)₂CHC₆H₄OMe, CSA, CH₂Cl₂, RT, 12 h, 70%; (d) DIBAL, CH₂Cl₂, −78 °C to 0 °C, 2 h, 95%; (e) TBSCl, imidazole, DMF, RT, 12 h, 88%; (f) OsO₄, NaIO₄, 2,6-lutidine, dioxane/H₂O (3:1), RT, 3 h, 82%; (g) H₂C=CHMgBr, MgBr₂·OEt₂, CH₂Cl₂, RT, 2 h, 72%; (h) MeOTf, 2,6-di-tert-butyl-4-methylpyridine, CH₂Cl₂, reflux, 6 h, 62%; (i) TBAF, THF, RT, 12 h, 94%; (j) DMP, CH₂Cl₂, RT, 40 min, 85%; (k) (PhO)₂P(O)CH(CH₃)CO₂C₂H₅, DBU/NaI, THF, −78 °C to 0 °C, 3 h, 60%; (l) DIBAL, CH₂Cl₂, −78 °C, 1 h, 96%.

Scheme 7

Dias’ synthesis. Synthesis of 8. Reagents and conditions: (a) TiCl₄, DIPEA, CH₂Cl₂, −78 °C to 0 °C; 1 h; (b) acrolein, −78 °C to 0 °C to RT, 12 h, 87% over two steps; (c) TBSOTf, 2,6-ludine, CH₂Cl_2, 0 °C, 20 min, 93%; (d) NMO, OsO4, cat., acetone/H₂O, 0 °C, 45 min, 67 (57%), 68 (20%); (e) CSA cat., 4-methoxybenzyl-2,2,2-trichloroacetimidate, CH₂Cl₂, RT, 12 h, 67%; (f) LiAlH₄, THF, −78 °C, 1 h, 75%; (g) TBSCl, imidazole, CH₂Cl₂, 0 °C, 1 h, 95%; (h) proton sponge, Me₃OBF₄, CH₂Cl₂, RT, 12 h, 75%; (i) DDQ/H₂O, CH₂Cl₂; RT, 2 h, 88%; (j) NMO, TPAP cat., CH₂Cl₂; RT, 1 h; (k) Cp₂TiMe₂, PhCH₃, 70 °C, 12 h, 50% over two steps; (l) HF-Py-THF, THF, RT, 12 h; 80%; (m) NMO, TPAP cat., CH₂Cl₂; 1 h, RT, (n) 75 in THF, NaH, RT, 12 h, 58% over two steps; (o) DIBAL, CH₂Cl₂, −15 °C, 1 h, 98%.

Scheme 8

Synthesis of C8 epimer of MGSTA-2. Reagents and conditions: (a) DCC, DMAP, 6-heptanoic acid, CH₂Cl₂, RT, 12 h, 92%; (b) Grubbs II catalyst, PhCH₃, reflux, 30 min, 80%; (c) HF, CH₂Cl₂/CH₃CN, RT, 24 h, 40%; (d) DCC, DMAP, (E)-2,6-heptadienoic acid, CH₂Cl₂, RT, 98%.

Scheme 9

Iqbal’s synthesis of 8. Reagents and conditions: (a) TiCl₄, 3-butenal, (−) spartein, CH₂Cl₂, 0 °C, 1 h, 83%; (dr 20:1); (b) TBSOTf, DIPEA, CH₂Cl₂, 0 °C, 90%; (c) NaBH₄, THF:H₂O, 90 h, 80%; (d) DMP, CH₂Cl₂, 2 h, 90%; (e) 63, NaI, DBU, −78 °C to 0 °C, THF, 3 h, Z:E, 95:5, 60%; (f) White catalyst 10%, p-benzoquinone, p-nitrobenzoic acid, 45 °C, 72 h, 84 (24%) and 85 (20%); (g) LiOH, THF/MeOH/H₂O, 4 h, 55 °C, 90%; (h) White catalyst 10%, p-benzoquinone, Cr(III)salenCl, 1,4-dioxane, 45 °C, 72 h, 40% (78% based on recovered starting material); (i) DIBAL, −78 °C to 0 °C, CH₂Cl₂, 2 h, 90%; (j) TBSCl, Imidazole, DMF, 2 h, 90%; (k) DTBMP, CH₂Cl₂, MeOTf, 6 h, reflux, 70%; (l) CSA, MeOH 2 h, 90%.

Scheme 10

Murphy’s synthesis of 8. Reagents and conditions: synthesis of 8, migrastatin 7 and MGSTA-3. Reagents and conditions: (a) vinyl benzoate, 92, PhCH₃, −20 °C, 48 h, 89%; (b) DAIB, TEMPO, CH₂Cl₂, 2.5 h, RT, 84%; (c) (i) sBuLi, THF, 15 min, −78 °C; (ii) (+)Ipc₂BOMe, −78 °C, 1 h; (iii) BF₃·Et₂O then 94, −78 °C, 20 h, then 1 M NaOH, 30% H₂O₂, RT, 20 h; (d) K₂CO₃, MeOH, RT, 18 h, 73% from 94; (e) TBSOTf, Et₃N, CH₂Cl₂, 0 °C, 1.5 h; (f) p-TSA, MeOH, 0 °C, 2 h, 84% over two steps; (g) Dess–Martin reagent, CH₂Cl₂, pyridine, RT, 18 h, 93%; (h) 63 in THF, NaH, 0 °C, 1.5 h, then 98 at −78 °C, 30 min, then 0 °C for 15 h, 79%; (i) DIBAL, CH₂Cl₂, −78 °C, 10 min, 90%.

Scheme 11

Synthesis of macrolacton migrastatin-core analogs. Reagents and conditions: (a) 99a–c, Ph₃P, DIAD, PhCH₃, RT; 100a (69%), 100b (76%); (b) Grubbs II catalyst, PhCH₃, reflux, 101a (68%), 101b (73%); (c) HF.py, THF, RT; MGSTA-8 (61%), MGSTA-11 (54%).

Scheme 12

Synthesis of macroketone migrastatin-core analogs. Reagents and conditions: (a) CBr₄, Ph₃P polymer-bound, CH₂Cl₂; (b) 32-102a,b, DBU, PhCH₃ then 31, RT; (c) Na/Hg, MeOH, RT; (103a (51%) 103b (51%), from 8; (d) Grubbs II catalyst, PhCH₃, reflux, 104a (99%), 104b (60%); (e) (i) 34, TMSCl, LHMDS, THF, 0 °C, 2 h; (ii) Pd(OAc)₂, CH₃CN, RT, 2 h, 78% from 34; (f) HF·Py, THF, RT, MGSTA-13 (90%); (g) HF·Py, THF, RT, MGSTA-9 (84%), MGSTA-12 (82%).

Scheme 13

Synthesis of macrothiolactone migrastatin-core analogs. Reagents and conditions: (a) Lawesson’s reagent, CH₂Cl₂, mw, 100 °C, 10 min; (b) 105a,b, Ph₃P, DIAD, PhCH₃, RT; 106a (42%), 106b (39%); (c) Grubbs II catalyst, CH₂Cl₂, mw, 100 °C, 30 min, 107b (49%); (d) Grubbs-II catalyst, PhCH₃, reflux, 107a (88%); (e) HF·Py, THF, RT; MGSTA-3 (85%), MGSTA-7 (63%).

Scheme 14

Reagents and conditions: (a) 109 TMSOTf, MS (AW300), CH₂Cl₂, −78 °C, 5 h, 60%; (b) TiCl₄, CDCl₃, 4 °C, 69%; (c) NaOH aq., MeOH, RT, 18 h, MGSTA-16 (61%), MGSTA-17 (73%).

Figure 4

(a) Structures of migrastatin (7) and migrastatin analogs MGSTA-1 to 4; (b) Chamber cell migration assay with 4T1 mammary mouse tumor cells and HUVECs; (c) metabolic stability of migrastatin and analogs; (d) inhibition of breast tumor metastasis (4T1) by MGSTA-2, MGSTA-3, MGSTA-4 in a mouse model. Lung metastasis was measured by the 6-thioguanine clonogenic assay. Results are mean ± SD (n = 5). *, p < 0.01. Adapted with permission from PNAS, 2005, 102, 3772. Copyright (2005) National Academy of Sciences, U.S.A. ^a Intensity of HPLC signal unchanged over 60 min of incubation.

Figure 5

(a) Structure of MGSTA-5; (b) Chamber cell migration assay; (c) MGSTA-5 treatment (40 mg/kg) begun at day 1 (Pre) or day 15 (Post) after tumor inoculation (MDA-MB-231). Primary tumor was resected at 2 weeks and tumor metastasis was determined by bioimaging at 3 weeks; (d) MGSTA-5 treatment (40 or 200 mg/kg) begun at day 1 after tumor inoculation (MDA-MB-231). Primary tumor was resected at 3 weeks and tumor metastasis was determined by bioimaging at 4 weeks. Adapted with permission from J. Am. Chem. Soc. 2010, 132, 3224. Copyright (2010) American Chemical Society.

Figure 6

(a) Structure of MGSTA-6 a; (b) Chamber cell migration assay with non-small lung carcinoma (NSLC) A549, H1975, H1299 cells; (c) Bioluminescent imaging of tumor metastasis at endpoint. Lung (Lu), liver (Li), heart (H), kidneys (K), and spleen (S). Adapted with permission from PNAS, 2011, 108, 15074.

Figure 7

(a) Structure of Biotin-conjugated MGSTA-3; (b) Quantification of actin bundling assay for the wild-type fascin and mutants; results are means and ± SD (n = 3); * p < 0.05 (c) Mutant sensitivity to MGSTA-3. Wild-type fascin and the E391A and H474A mutants of fascin were assayed for their actin-bundling activity in the absence or presence of MGSTA-3 (10 µM); results are means and ±SD (n = 3). * p < 0.05; (d) Boyden chamber cell migration assay of mouse fascin shRNA-treated 4T1 cells transfected with various mutants of GFP–human fascin (h-fascin) in the presence or absence of MGSTA-3 (10 µM); results are means and ± SD (n = 5) p < 0.05; (e) Tumor metastasis assay with mouse fascin shRNA-treated 4T1 cells overexpressing wild-type human fascin or fascin (H474A) mutant in the presence or absence of MGSTA-3 (10 mg/kg). Comparison of the fascin shRNA group with the control shRNA group. Results are means and ±SD (n = 5~6). *, p < 0.05 Adapted by permission from Macmillan Publishers Ltd: Nature, 2010, 464, 1062, copyright (2010) http://www.nature.com/.

Figure 8

(a) Structure of MGSTA-13; (b) Chamber cell migration assay with canine mammary cancer cell lines; (c) Growth characteristics of CMT-W1, cell lines cultured on Matrigel and treated with MGSTA-13 100 µM for 24 h; (d) Quantification of fascin1 and F-actin co-localization at merge images; the unpaired t-test was applied. p < 0.01 (e) Representative confocal microscopy images of cytoskeletal protein F-actin and fascin1 in CMT-W1M canine carcinoma cell line; (f) Expression of phospho-FSCN1(Ser39) in canine mammary cancer cell lines; the unpaired t-test was applied. * p < 0.05. Adapted from PLoS ONE, 2013, 8, e76789.

Figure 9

Structures of selected migrastatin analogs and effect on human breast cancer cell lines MCF7 and MDA MB-361 assessed with Boyden chamber assay.