Reduced miR-371b-5p expression drives tumor progression via CSDE1/RAC1 regulation in triple-negative breast cancer.

Triple-negative breast cancer (TNBC) is the most aggressive subtype of breast cancer; however, specific prognostic biomarkers have not yet been developed. In this study, we identified dysregulated microRNAs (miRNAs) in TNBC by profiling miRNA and mRNA expression. In patients with TNBC, miR-371b-5p expression was reduced, and miR-371b-5p overexpression significantly mitigated TNBC cell growth, migration, and invasion. In addition, we found that expression of cold shock domain-containing protein E1 (CSDE1), a direct target gene of miR-371b-5p, was upregulated in TNBC cells, and inhibition of CSDE1 expression alleviated TNBC cell growth by regulating RAC1 transcription. Mechanistically, CSDE1, phosphorylated C-terminal domain (p-CTD) of RNA polymerase II (RNAPII), and CDK7 form a complex, and downregulation of CSDE1 leads to weak interaction between RNAPII p-CTD and CDK7, resulting in a decrease in RNAPII p-CTD expression to reduce RAC1 transcript levels in CSDE1-deficient TNBC cells. Our data demonstrate that miR-371b-5p is a tumor-suppressive miRNA that regulates the CSDE1/Rac1 axis and could be a potential prognostic biomarker for TNBC.

Inhibition of Chk1 by miR-320c increases oxaliplatin responsiveness in triple-negative breast cancer.

Checkpoint kinase 1 (Chk1) expression is enhanced in most cancers owing to oncogenic activation and constant replicative stress. Chk1 inactivation is a promising cancer therapy, as its inactivation leads to genomic instability, chromosomal catastrophe, and cancer cell death. Herein, we observed that miR-320c, downregulated in triple-negative breast cancer (TNBC) patients, can target Chk1. In addition, downregulated miR-320c expression was associated with poor overall survival in TNBC patients. As Chk1 was associated with the DNA damage response (DDR), we investigated the effect of miR-320c on DDR in TNBC cells. To induce DNA damage, we used platinum-based drugs, especially oxaliplatin, which is most effective with miR-320c. We observed that overexpression of miR-320c in TNBC regulated the oxaliplatin responsiveness by mediating DNA damage repair through the negative regulation of Chk1 in vitro. Furthermore, using a xenograft model, a combination of miR-320c mimic and oxaliplatin effectively inhibited tumor progression. These investigations indicate the potential of miR-320c as a marker of oxaliplatin responsiveness and a therapeutic target to increase the efficacy of chemotherapy in TNBC.

Production of three phenylethanoids, tyrosol, hydroxytyrosol, and salidroside, using plant genes expressing in Escherichia coli.

Polyphenols, which include phenolic acids, flavonoids, stilbenes, and phenylethanoids, are generally known as useful antioxidants. Tyrosol, hydroxytyrosol, and salidroside are typical phenylethanoids. Phenylethanoids are found in plants such as olive, green tea, and Rhodiola and have various biological activities, including the prevention of cardiovascular diseases, cancer, and brain damage. We used Escherichia coli to synthesize three phenylethanoids, tyrosol, hydroxytyrosol, and salidroside. To synthesize tyrosol, the aromatic aldehyde synthase (AAS) was expressed in E. coli. Hydroxytyrosol was synthesized using E. coli harboring AAS and HpaBC, which encodes hydroxylase. In order to synthesize salidroside, 12 uridine diphosphate-dependent glycosyltransferases (UGTs) were screened and UGT85A1 was found to convert tyrosol to salidroside. Using E. coli harboring AAS and UGT85A1, salidroside was synthesized. Through the optimization of these three E. coli strains, we were able to synthesize 531 mg/L tyrosol, 208 mg/L hydroxytyrosol, and 288 mg/L salidroside, respectively.

Synthesis and biological evaluation of an albumin-binding prodrug of doxorubicin that is cleaved by prostate-specific antigen (PSA) in a PSA-positive orthotopic prostate carcinoma model (LNCaP).

The prostate-specific antigen (PSA) is a serine protease that is over-expressed in prostate carcinoma and represents a molecular target for selectively releasing an anticancer agent from a prodrug formulation. We have recently investigated a macromolecular prodrug strategy for improved cancer chemotherapy based on 2 features: (i) rapid and selective binding of thiol-reactive prodrugs to the cysteine-34 position of endogenous albumin after intravenous administration, and (ii) enzymatic release of the albumin-bound drug at the tumor site (Mansour et al., Cancer Res 2003, 63, 4062-4066). In this work, we describe an albumin-binding prodrug, EMC-Arg-Ser-Ser-Tyr-Tyr--Ser-Arg-DOXO [EMC: epsilon-Maleimidocaproic acid; DOXO = doxorubicin; X = amino acid] that is cleaved by PSA. Because of the incorporation of 2 arginine residues, the prodrug exhibited excellent water-solubility and was rapidly and selectively bound to endogenous albumin. Incubation studies with PSA and tumor homogenates from PSA-positive tumors (LNCaP) demonstrated that the albumin-bound form of the prodrug was efficiently cleaved by PSA at the P(1)-P' (1) scissile bond releasing the doxorubicin dipeptide H-Ser-Arg-DOXO, which was further degraded to doxorubicin as the final cleavage product. In cell culture experiments, the prodrug was approximately 100-fold less active against LNCaP cells than the free drug. In contrast, in a mouse model of human prostate cancer using luciferase transduced LNCaP cells orthotopically implanted in SCID mice, the prodrug showed enhanced antitumor efficacy when compared to doxorubicin. Doxorubicin treatment at a dose of 2 x 4 mg/kg caused significant weight loss and mortality (-25%), and did not result in a significant antitumor response at the end of the experiment. The prodrug at 3 x 12 mg/kg doxorubicin equivalents, however, was well tolerated and induced a significant reduction in tumor size of 62% (+/-25%, **p = 0.003) as well as a decrease of the metastatic burden in the lungs as detected in luciferase assays (-50%, SD +/- 115%, *p = 0.038).

Albumin-binding prodrugs of camptothecin and doxorubicin with an Ala-Leu-Ala-Leu-linker that are cleaved by cathepsin B: synthesis and antitumor efficacy.

We have recently validated a macromolecular prodrug strategy for improved cancer chemotherapy based on two features: (a) rapid and selective binding of thiol-reactive prodrugs to the cysteine-34 position of endogenous albumin and (b) acid-sensitive promoted or enzymatic release of the drug at the tumor site [Kratz, F., Warnecke, A., Scheuemann, K., Stockmar, C., Schwab, J., Lazar, P., Druckes, P., Esser, N., Drevs, J., Rognan, D., Bissantz, C., Hinderling, C., Folkers, G., Fichtner, I., and Unger, C. (2002) J. Med. Chem. 45, 5523-33]. In the present work, we developed water-soluble camptothecin (CPT) and doxorubicin (DOXO) prodrugs that incorporate the peptide linker Ala-Leu-Ala-Leu that serves as a substrate for the tumor-associated protease, cathepsin B, which is overexpressed in several solid tumors. Consequently, two albumin-binding prodrugs were synthesized [EMC-Arg-Arg-Ala-Leu-Ala-Leu-Ala-CPT (1) and EMC-Arg-Arg-Ala-Leu-Ala-Leu-DOXO (2) (EMC = 6-maleimidocaproic acid)]. Both prodrugs exhibited excellent water-solubility and bound rapidly and selectively to the cysteine-34 position of endogenous albumin. Further in vitro studies showed that the albumin-bound form of the prodrugs was cleaved specifically by cathepsin B as well as in human tumor homogenates. Major cleavage products were CPT-peptide derivatives and CPT for the CPT prodrug and H-Leu-Ala-Leu-DOXO, H-Leu-DOXO, and DOXO for the doxorubicin prodrug. In vivo, 1 was superior to free camptothecin in an HT-29 human colon xenograft model; the antitumor efficacy of prodrug 2 was comparable to that of free doxorubicin in the M-3366 mamma carcinoma xenograft model at equimolar doses.

Development of a novel albumin-binding prodrug that is cleaved by urokinase-type-plasminogen activator (uPA).

A water-soluble albumin-binding prodrug of doxorubicin [EMC-Gly-Gly-Gly-Arg-Arg-DOXO (EMC, 6-maleimidocaproic acid)] was developed that is cleaved specifically by the tumor-associated protease urokinase-type plasminogen activator (uPA).