Dual PI3K-BRD4 Inhibitor SF1126 Inhibits Colorectal Cancer Cell Growth in Vitro and in Vivo.

BACKGROUND/AIMS: Bromodomain-containing protein 4 (BRD4) and phosphatidylinositol 3-kinase (PI3K) are key oncogenic cascades in colorectal cancer (CRC). SF1126 is a novel and potent PI3K-BRD4 dual inhibitor. METHODS: CRC cells and human colon epithelial cells were treated with SF1126. Cell survival was tested by MTT and soft agar colony formation assays. Cell proliferation was tested by BrdU ELISA method. Cell apoptosis was tested by a TUNEL staining method and Histone DNA ELISA. Western blotting was utilized to test the signaling proteins. A HT-29 xenograft mice model was established to study the anti-tumor activity of SF1126 in vivo. RESULTS: SF1126 potently inhibited the survival, proliferation, and progression of the cell cycle in an established CRC cell line (HT-29) and primary human colon cancer cells. Significant activation of apoptosis was detected in SF1126-treated CRC cells. In CRC cells, SF1126 blocked Akt-mammalian target of rapamycin (mTOR) complex1/2 signaling and downregulated BRD4 target proteins (Myc and cyclin D1). Further studies showed that SF1126 activated p38 signaling in CRC cells. In contrast, the p38 inhibitors or p38 short hairpin RNA inhibited SF1126-induced cytotoxicity and apoptosis in CRC cells. In vivo, subcutaneous administration of SF1126 significantly inhibited HT-29 xenograft tumor growth in nude mice. CONCLUSION: SF1126 inhibits CRC cell growth possibly by targeting PI3K-Akt-mTOR, BRD4, and p38 signaling.

The therapeutic effect of the BRD4-degrading PROTAC A1874 in human colon cancer cells.

A1874 is a novel BRD4-degrading proteolysis targeting chimera (PROTAC). In primary colon cancer cells and established HCT116 cells, A1874 potently inhibited cell viability, proliferation, cell cycle progression, as well as cell migration and invasion. The BRD4-degrading PROTAC was able to induce caspase and apoptosis activation in colon cancer cells. Furthermore, A1874-induced degradation of BRD4 protein and downregulated BRD-dependent genes (c-Myc, Bcl-2, and cyclin D1) in colon cancer cells. Significantly, A1874-induced anti-colon cancer cell activity was more potent than the known BRD4 inhibitors (JQ1, CPI203, and I-BET151). In BRD4-knockout colon cancer cells A1874 remained cytotoxic, indicating the existence of BRD4-independent mechanisms. In addition to BRD4 degradation, A1874 cytotoxicity in colon cancer cells was also associated with p53 protein stabilization and reactive oxygen species production. Importantly, the antioxidant N-acetyl-cysteine and the p53 inhibitor pifithrin-α attenuated A1874-induced cell death and apoptosis in colon cancer cells. In vivo, A1874 oral administration potently inhibited colon cancer xenograft growth in severe combined immuno-deficient mice. BRD4 degradation and p53 protein elevation, as well as apoptosis induction and oxidative stress were detected in A1874-treated colon cancer tissues. Together, A1874 inhibits colon cancer cell growth through both BRD4-dependent and -independent mechanisms.

Preclinical study of cinobufagin as a promising anti-colorectal cancer agent.

Here, we assessed the anti-colorectal cancer (CRC) cell activity of cinobufagin (CBG). We found that CBG exerted potent cytotoxic and anti-proliferative activity against CRC lines (HCT-116 and HT-29) and primary human CRC cells. Meanwhile, it activated apoptosis, and disrupted cell-cycle progression in the cells. At the signaling level, CBG treatment in CRC cells provoked endoplasmic reticulum stress (ER stress), the latter was evidenced by caspase-12 activation, CHOP expression, as well as PERK and IRE1 phosphorylations. Contrarily, the ER stress inhibitor salubrinal, the caspase-12 inhibitor and CHOP shRNA remarkably attenuated CBG-induced CRC cell death and apoptosis. Further, CBG in-activated mammalian target or rapamycin complex 1 (mTORC1), which appeared responsible for proliferation inhibition in CRC cells. Introduction of a constitutively-active S6K1 ("ca-S6K1") restored proliferation of CBG-treated CRC cells. Finally, CBG intraperitoneal injection suppressed HCT-116 xenograft tumor growth in the nude mice. CHOP upregulation and mTORC1 in-activation were also noticed in CBG-treated HCT-116 tumors. The results of this preclinical study suggest that CBG could be tested as promising anti-CRC agent.

Pre-clinical characterization of PKC412, a multi-kinase inhibitor, against colorectal cancer cells.

The potential effect of PKC412, a small molecular multi-kinase inhibitor, in colorectal cancer (CRC) cells was evaluated here. We showed that PKC412 was cytotoxic and anti-proliferative against CRC cell lines (HT-29, HCT-116, HT-15 and DLD-1) and primary CRC cells. PKC412 provoked caspase-dependent apoptotic death, and induced G2-M arrest in the CRC cells. AKT activation was inhibited by PKC412 in CRC cells. Reversely, expression of constitutively-active AKT1 (CA-AKT1) decreased the PKC412's cytotoxicity against HT-29 cells. We propose that Bcl-2 could be a primary resistance factor of PKC412. ABT-737, a Bcl-2 inhibitor, or Bcl-2 siRNA knockdown, dramatically potentiated PKC412's lethality against CRC cells. Forced Bcl-2 over-expression, on the other hand, attenuated PKC412's cytotoxicity. Significantly, PKC412 oral administration suppressed AKT activation and inhibited HT-29 tumor growth in nude mice. Mice survival was also improved with PKC412 administration. These results indicate that PKC412 may have potential value for CRC treatment.

[Total laparoscopic sigmoid and rectal surgery combined with transanal endoscopic microsurgery].

OBJECTIVE: To investigate the feasibility and short-term outcomes of total laparoscopic sigmoid and rectal surgery combined with transanal endoscopic microsurgery(TEM). METHODS: The clinical data of 26 patients with colorectal carcinoma treated by total laparoscopic surgery with TEM between May 2010 and May 2011 in the Shanghai Ruijin Hospital were retrospectively analyzed. RESULTS: All the 26 operations were successfully accomplished laparoscopically. There was no conversion to open procedure. No diverting ileostomy was made. The mean operative time was (151.6±25.9) min. The mean blood loss was (200.2±114.7) ml. The mean time to first flatus was (2.0±0.5) d. The mean tumor size was (3.0±0.7) cm and all resection margins were negative. The mean number of lymph nodes harvested was (12.9±2.2). Six patients developed postoperative anastomotic leakage, all of who had tumors in the lower rectum. There were no ureteral injury, intestinal obstruction, or pulmonary infection. CONCLUSIONS: Total laparoscopic sigmoid and rectal surgery combined with TEM is a safe and feasible minimally invasive surgery. It is an improvement by combining laparoscopic skills with the concept of natural orifice transluminal endoscopic surgery.