(2E,4E,6Z,8Z)-8-(3’,4’-Dihydro-1’(2H)-naphthalen-1’-ylidene)-3,7-dimethyl-2,3,6-octatrienoinic acid, 9cUAB30, is a selective rexinoid for the retinoid X nuclear receptors (RXR). 9cUAB30 displays substantial chemopreventive capacity with little toxicity and is being translated to the clinic as a novel cancer prevention agent. To improve on the potency of 9cUAB30, we synthesized 4-methyl analogs of 9cUAB30, which introduced chirality at the 4-position of the tetralone ring. The syntheses and biological evaluations of the racemic homolog and enantiomers are reported. We demonstrate that the S-enantiomer is the most potent and least toxic even though these enantiomers bind in a similar conformation in the ligand binding domain of RXR.

Epidemiologic studies have shown that diabetics receiving the biguanide metformin, as compared to sulfonylureas or insulin, have a lower incidence of breast cancer. Metformin increases levels of activated AMPK and decreases circulating IGF-1; encouraging its potential use in both cancer prevention and therapeutic settings. In anticipation of clinical trials in non-diabetic women, the efficacy of metformin in non-diabetic rat and mouse mammary cancer models was evaluated. Metformin was administered by gavage or in the diet, at a human equivalent dose, in standard mammary cancer models: (1) methylnitrosourea (MNU)-induced ER+ mammary cancers in rats, and (2) MMTV-Neu/P53KO ER- mammary cancers in mice. In the MNU rat model, metformin dosing (150 or 50 mg/Kg BW/day, by gavage) was ineffective in decreasing mammary cancer multiplicity, latency, or weight. Pharmacokinetic studies of metformin (150 mg/kg BW/day, by gavage) yielded plasma levels (Cmax and AUC) higher than humans taking 1.5 g/day. In rats bearing small palpable mammary cancers, short-term metformin (150 mg/kg BW/day) treatment increased levels of phospho-AMPK and phospho-p53 (Ser20) but failed to reduce Ki67 labeling or expression of proliferation-related genes. In the mouse model, dietary metformin (1500 mg/kg diet) did not alter final cancer incidence, multiplicity, or weight. Metformin did not prevent mammary carcinogenesis in two mammary cancer models; raising questions about metformin efficacy in breast cancer in non-diabetic populations.

Trauma-hemorrhage produces immunodepression in males but not in proestrus females and this difference is due to the presence of high estrogen in proestrus females. Although skin is the largest immunological organ of the body and is considered the first line of defense, no study to-date has examined whether trauma-hemorrhage has any effects on keratinocytes which are the major epidermal cell type (>90%) of skin. We therefore examined whether epidermal keratinocytes inflammatory response and the signal transduction pathways involved in the inflammatory response are altered following trauma-hemorrhage. C3H/HeN mice were subjected to trauma-hemorrhage and 2 hrs thereafter; keratinocytes were harvested and stimulated with LPS for 24 hrs (5μg/ml). Inflammatory mediators, Toll like receptor (TLR) and myeloid differentiation adaptor protein (MyD88) expression, and the activation of mitogen-activated protein kinase (MAPK) were determined. Trauma-hemorrhage increased the production of IL-6, IL-10, IL-12 and TNF-α, enhanced the expression of TLR4, MyD88 as well as the activation of MAPK proteins (p38, ERK and JNK) in epidermal keratinocytes. However, administration of a single dose of 17β-estradiol following trauma-hemorrhage prevented the increase in these inflammatory parameters under those conditions. These findings suggest that 17β-estradiol normalizes epidermal keratinocytes inflammatory responses following trauma-hemorrhage by preventing the upregulation of TLR4-mediated MAPK activation.

Although 17beta-estradiol (E2) is reported to improve the inflammatory response after trauma-hemorrhage (T-H), it remains unknown whether E2 plays any role in the central nervous system after T-H. Microglial cells, resident central macrophages, are thought to play a central role in exacerbating cell-mediated inflammation. We hypothesized that T-H up-regulates microglial cell-mediated inflammatory response in the brain, and E2 produces central anti-inflammatory effects via negative regulation of microglial cells. Male Sprague-Dawley rats were subjected to sham operation (cannulation plus laparotomy) or T-H (midline laparotomy; mean blood pressure, 35 +/- 5 mmHg for 90 min followed by resuscitation) and immediately killed after resuscitation. Rats received vehicle or E2 (1 mg/kg body weight i.v.) at the onset of resuscitation. In other experiments, minocycline (40 mg/kg body weight i.p.), microglia inhibitor, was administered 1 h before T-H to prevent inflammatory response in the microglia after T-H. The plasma and hypothalamic tumor necrosis factor (TNF-alpha) levels were increased, along with the activation of microglial cells in T-H rats compared with shams. Furthermore, T-H increased microglial TNF-alpha productive capacity in vitro. 17beta administration after T-H prevented these inflammatory responses. In rats pretreated with minocycline, decreased microglial TNF-alpha production and hypothalamic TNF-alpha levels were observed, but plasma TNF-alpha levels were not altered after T-H. Thus, T-H induces inflammatory responses even in the hypothalamus, and E2 seems to be a useful adjunct for down-regulating microglial cell-mediated inflammatory response after T-H.

Daily dosing of either NSAIDs or EGFR inhibitors has been shown to prevent bladder cancer development in a N-butyl-(4-hydroxybutyl)nitrosamine (OH-BBN)-induced rat model. However, these inhibitors cause gastrointestinal ulceration and acneiform rash, respectively, limiting their continuous use in a clinical prevention setting. We studied chemopreventive efficacy of pulsatile dosing of EGFR inhibitor erlotinib (42 mg/kg BW, once/week) combined with intermittent or continuous low doses of the NSAID naproxen (30 mg/kg BW/day, 3 weeks on/off or 128 ppm daily in diet) in the OH-BBN induced rat bladder cancer model. The interventions were started either at 1 or 4 weeks (early intervention) or 3 months (delayed intervention) after the last OH-BBN treatment, by which time the rats had developed microscopic bladder lesions. All combination regimens tested as early versus late intervention led to the reduction of the average bladder tumor weights (54%–82%; P < 0.01 to P < 0.0001), a decrease in tumor multiplicity (65%–85%; P < 0.01 to P < 0.0001), and a decrease in the number of rats with large palpable tumors (>200 mg; 83%–90%; P < 0.01 to P < 0.0001). Levels of signal transduction markers, Ki-67, cyclin D1, IL1β, pSTAT3, and pERK, were significantly (P < 0.05 to P < 0.001) reduced in the treated tumors, demonstrating their potential utility as predictive markers for efficacy. These findings demonstrate that significant chemopreventive efficacy could be achieved with alternative intervention regimens designed to reduce the toxicity of agents, and that starting erlotinib and/or naproxen treatments at the time microscopic tumors were present still conferred the efficacy.