Study of post-natal effect of chemopreventive agents on ethylnitrosourea-induced transplacental carcinogenesis in rats. III. Inhibitory action of indomethacin, voltaren, theophylline and epsilon-aminocaproic acid

Keeping RNA polymerase II on the run: Functions of MLL fusion partners in transcriptional regulation

Since the identification of key MLL fusion partners as transcription elongation factors regulating expression of HOX cluster genes during hematopoiesis, extensive work from the last decade has resulted in significant progress in our overall mechanistic understanding of role of MLL fusion partner proteins in transcriptional regulation of diverse set of genes beyond just the HOX cluster. In this review, we are going to detail overall understanding of role of MLL fusion partner proteins in transcriptional regulation and thus provide mechanistic insights into possible MLL fusion protein-mediated transcriptional misregulation leading to aberrant hematopoiesis and leukemogenesis.

The inhibiting activity of meadowsweet extract on neurocarcinogenesis induced transplacentally in rats by ethylnitrosourea

Inhibitory activity of a decoction of meadowsweet, given postnatally, was studied in rats at risk for neurogenic and renal tumors initiated by transplacental exposure to ethylnitrosourea (ENU). Chemical analysis of ethanol and aqueous extracts of meadowsweet has shown high content of biologically active flavonoids and tannins. Pregnant rats of LIO strain were given a single i.v. injection of ENU, 75 mg/kg, оn the 21st day of gestation. After weaning at 3 weeks after birth, the offspring were divided into two groups: the first was a positive control (ENU), while rats in the second group (ENU + meadowsweet) were given daily a decoction of meadowsweet as drinking water throughout their lifetime. All rats of the first group (ENU) developed multiple malignant tumors, which occurred in brain (86%), spinal cord (43%), peripheral and cranial nerves (29%) and in kidney (31%). More than one-third of CNS tumors were oligodendrogliomas. Mixed gliomas (oligoastrocytomas) occurred less frequently. All other types including astrocytomas, glioblastomas, and ependymomas were rare. All PNS tumors were neurinomas (schwannomas). The spectrum of tumors was similar in rats of the second group. Postnatal consumption of meadowsweet significantly reduced number of tumor-bearing rats (by 1.2 times), the incidence and multiplicity of CNS tumors (brain-by 2.0 and 2.1 times, respectively; spinal cord-by 3.1 and 3.0 times, respectively) and significantly increased latency period, compared to rats of the first group. No significant reduction in PNS or renal tumors was seen in rats given meadowsweet. Meadowsweet extract can be considered an effective cancer preventive agent especially as a neurocarcinogenesis inhibitor.

A distinct phenotypic change in gliomas at the time of magnetic resonance imaging detection

Object

Although gliomas remain refractory to treatment, it is not clear whether this characteristic is fixed at the time of its origin or develops later. The authors have been using a model of neurocarcinogenesis to determine whether a time exists during a glioma's evolution during which it is detectable but still curable, thus providing a justification for exploring the clinical merits of an early detection and treatment strategy. The authors recently reported the presence of 2 distinct cellular subsets, 1 expressing nestin and the other both glial fibrillary acidic protein (GFAP) and osteopontin (OPN), within all examined gliomas that developed after in utero exposure to ethylnitrosourea.

Methods

In this study, the authors used magnetic resonance (MR) imaging to assess when these 2 subpopulations appeared during glioma evolution.

Results

Using T2-weighted and diffusion-weighted MR imaging, the authors observed that gliomas grew exponentially once detected at rates that were location-dependent. Despite large differences in growth rates, however, they determined by correlating histochemistry with imaging in a second series of animals, that all lesions initially detected on T2-weighted images contained both subsets of cells. In contrast, lesions containing only nestin-positive cells, which appeared on average 40 days before detection on MR images, were not detected.

Conclusions

The sequential appearance of first the nestin-positive cells followed several weeks later by those expressing GFAP/OPN suggests that all gliomas arise through common early steps in this model. Furthermore, the authors hypothesize that the expression of OPN, a molecule associated with cancer aggressiveness, at the time of T2-weighted detection signals a time during glioma development when the lesion becomes refractory to treatment.

Magnetic resonance imaging of ethyl-nitrosourea-induced rat gliomas: a model for experimental therapeutics of low-grade gliomas

Human low-grade gliomas represent a population of brain tumors that remain a therapeutic challenge. Preclinical evaluation of agents, to test their preventive or therapeutic efficacy in these tumors, requires the use of animal models. Spontaneous gliomas develop in models of chemically induced carcinogenesis, such as in the transplacental N-ethyl-N-nitrosourea (ENU) rat model. However, without the ability to detect initial tumor formation, multiplicity or to measure growth rates, it is difficult to test compounds for their interventional or preventional capabilities. In this study Fisher-334 rats, treated transplacentally with ENU, underwent magnetic resonance imaging (MRI) examination in order to evaluate this approach for detection of tumor formation and growth. ENU-induced intracranial cerebral tumors were first observable in T2-weighted images beginning at 4 months of age and grew with a mean doubling time of 0.487 +/- 0.112 months. These tumors were found histologically to be predominately mixed gliomas. Two therapeutic interventions were evaluated using MRI, vitamin A (all-trans retinol palmitate, RP), as a chemopreventative agent and the anti-angiogenic drug SU-5416. RP was found to significantly delay the time to first tumor observation by one month (P = 0.05). No differences in rates of tumor formation or growth rates were observed between control and RP-treated groups. MRI studies of rats treated with SU-5416 resulted in reduction in tumor growth rates compared to matched controls. These results show that MRI can be used to provide novel information relating to the therapeutic efficacy of agents against the ENU-induced tumor model.

Effect of the protein kinase inhibitors, 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine H-7 and N-(2-[methylamino]ethyl)-5-isoquinoline-sulfonamide H-8 on Lewis lung carcinoma tumor progression

The effects of 1-(5-isoquinolinylsulfonyl)-2-methylpiperazine H-7 (a cAMP-dependent protein kinase and protein kinase C inhibitor), n-(2-[methylamino]ethyl)-5-isoquinoline-sulfonamide H-8 (a cAMP- and cGMP-dependent protein kinase inhibitor) and indomethacin (IND, a cyclooxygenase inhibitor) on both the spontaneous metastatic ability of 3LL (Lewis lung carcinoma) tumor cells and anti-tumor host response were studied. The study of tumor progression showed that H-7 and H-8 (2 mg kg(-1) day(-1) , i.p., for 8 days) significantly reduced the mean number of metastases (0.8 +/- 0.2 and 1.0 +/- 0.7, respectively, P < 0.05) with respect to the number of lung metastases (4.2 +/- 2.1) observed in the control group. In turn, the highest tumor-specific cytotoxicity response (50% increase vs. non-treated target cells) was observed when both animal and tumor cells were treated with H-8. This suggests that the protein kinase inhibitors could inhibit tumor progression toward lung metastases formation by blocking the immunosuppressor mechanism triggered by agents that increase intracellular cAMP.

Increased telomerase activity and absence of p53 mutation in oligoastrocytomas induced by N-ethyl-N-nitrosourea in rats

The question of whether the changes in telomerase activity and/or the alteration of the p53 gene are involved in the development of oligo-astrocytomas induced by N-ethyl-N-nitrosourea (ENU) in rats was addressed. Telomerase activity levels of oligo-astrocytomas, including early neoplastic lesions, were significantly increased as compared to the normal controls, correlating with the degree of malignancy. In contrast, no mutations of p53 exons 5-7 were found in early neoplastic lesions or oligo-astrocytomas. These results indicate that the activation of telomerase occurs during astrocytoma carcinogenesis and contributes to the development of brain tumors, but the alterations of p53, at least on exons 5-7, may not be involved in this process.