Combination of dexamethasone and a somatostatin analogue in the treatment of advanced prostate cancer

The local microenvironment at the sites of cancer metastases protects tumour cells from anticancer drug-induced apoptosis via mechanisms, such as soluble growth factors and cytokines. The concept of antisurvival factor (ASF) therapy as a component of anticancer treatments aims at neutralising the protective effect conferred upon cancer cells by the survival factor(s) derived by the local microenvironment, in order to enhance the sensitivity and/or reverse the resistance of tumour cells to other anticancer therapeutic strategies. Herein, we review the translation of this concept from ex vivo studies to clinical applications in the setting of prostate cancer refractory to androgen ablation (stage D3). At this stage, which predominantly involves bone metastases, insulin-like growth factor 1 (IGF-1) production (either growth hormone (GH)-dependent or GH-independent) can protect tumour cells from apoptosis, despite the significant suppression of androgens. The application of the ASF therapeutic concept involves the combination of dexamethasone (which suppresses GH-independent IGF-1) and somatostatin analogue (which suppresses endocrine, GH-dependent IGF-1) with the pro-apoptotic effect of the testicular androgen suppression by sustained use of LHRH analogues. In stage D3, patients who had failed anti-androgen withdrawal, chemotherapy and also had several other adverse prognostic features, the ASF-based combination achieved durable objective responses and major symptomatic improvement, paving the way for future applications of this approach. The ASF-based combination therapy illustrates a novel paradigm in cancer treatment: anti-tumour treatment strategies may not only aim at directly inducing cancer cell apoptosis, but can also target the tumour microenvironment and neutralise the protection it confers on metastatic cancer cells. The favourable toxicity profile of this therapeutic approach calls for its testing in a randomised controlled setting in metastatic prostate cancer and, conceivably, in other IGF-1-responsive malignancies.     

Presence and consequence of uracil in preneoplastic DNA from folate/methyl-deficient rats

Uracil can arise in DNA by misincorporation of dUTP into nascent DNA and/or by cytosine deamination in established DNA. Based on recent findings, both pathways appear to be promoted in the methyl-deficient model of hepatocarcinogenesis. A chronic increase in the ratio dUTP:dTTP with folate/methyl deficiency can result in a futile cycle of excision and reiterative uracil misincorporation leading to premutagenic apyrimidinic (AP) sites, DNA strand breaks, DNA fragmentation and apoptotic cell death. The progressive accumulation of unmethylated cytosines with chronic methyl deficiency will increase the potential for cytosine deamination to uracil and further stress uracil mismatch repair mechanisms. Uracil is removed by a highly specific uracil-DNA glycosylase (UDG) leaving an AP site that is subsequently repaired by sequential action of AP endonuclease, 5'-phosphodiesterase, a DNA polymerase and DNA ligase. Since the DNA polymerases cannot distinguish between dUTP and dTTP, an increase in dUTP:dTTP ratio will promote uracil misincorporation during both DNA replication and repair synthesis. The misincorporation of uracil for thymine (5-methyluracil) may constitute a genetically significant form of DNA hypomethylation distinct from cytosine hypomethylation. In the present study a significant increase in the level of uracil in liver DNA as early as 3 weeks after initiation of folate/methyl deficiency was accompanied by parallel increases in DNA strand breaks, AP sites and increased levels of AP endonuclease mRNA. In addition, uracil was also detected within the p53 gene sequence using UDG PCR techniques. Increased levels of uracil in DNA implies that the capacity for uracil base excision repair is exceeded with chronic folate/methyl deficiency. It is possible that enzyme-induced extrahelical bases, AP sites and DNA strand breaks interact to negatively affect the stability of the DNA helix and stress the structural limits of permissible uracil base excision repair activity. Thus substitution of uracil for thymine induces repair- related premutagenic lesions and a novel form of DNA hypomethylation that may relate to tumor promotion in the methyl-deficient model of hepatocarcinogenesis.      

Role of exosomes in treatment of hepatocellular carcinoma

Exosomes are nanovesicles that may play a role in intercellular communication by acting as carriers of functional contents such as proteins, lipids, RNA molecules and circulating DNA from donor to recipient cells. In addition, exosomes may play a potential role in immunosurveillance and tumor pathogenesis and progression. Recently, research has increasingly focused on the role of exosomes in hepatocellular carcinoma (HCC), the most common primary liver malignancy. We herein review data on emerging experimental and clinical studies focused on the role of exosomes in the pathogenesis, diagnosis, progression and chemotherapy response of patients with HCC. Beyond their diagnostic value in HCC, exosomes are involved in different mechanisms of HCC tumor pathogenesis and progression including angiogenesis and immune escape. Moreover, exosomes have been demonstrated to change the tumor microenvironment to a less tolerogenic state, favoring immune response and tumor suppression. These results underline a practical and potentially feasible role of exosomes in the treatment of patients with HCC, both as a target and a vehicle for drug design. Future studies will need to further elucidate the exact role and reliability of exosomes as screening, diagnostic and treatment targets in patients with HCC.     

Induction of TrkA expression by differentiation inducers in human myeloid leukemia KG-1 cells

We have recently reported that retinoic acid (RA) induced the expression of trkA, the high affinity receptor for nerve growth factor (NGF), in human myeloid leukemia KG-1 cells. In the present study, we report that the expression of trkA was also induced by several other differentiation inducers, including 1alpha, 25-dihydroxyvitamin D3 (Vit D3), 1-beta-D-arabinofuranosyl cytosine (Ara-C), sodium butyrate (NaBut), and phorbol 12-myristate 13-acetate (PMA). Interestingly, RA in combination with NaBut or PMA synergistically induced cellular differentiation as well as the expression of trkA in KG-1 cells. Furthermore, activation of the induced trkA receptor by exogenous NGF potentiated the differentiating effects of RA and NaBut. Our results demonstrated that the induction of trkA is an event associated with the differentiation of KG-1 cells. Our findings suggest that NGF, in addition to its pivotal roles in the nervous system, may also play important roles in hematopoietic differentiation.     

Hepatic Injury Due to Combined Choline-Deprivation and Thioacetamide Administration: An Experimental Approach to Liver Diseases

Background

The induction of prolonged choline-deprivation (CD) in rats receiving thioacetamide (TAA) is an experimental approach of mild hepatotoxicity that could resemble commonly presented cases in clinical practice (in which states of malnutrition and/or alcoholism are complicated by the development of other liver-associated diseases).

Aim

The present study aimed to investigate the time-dependent effects of a 30-, a 60- and a 90-day dietary CD and/or TAA administration on the adult rat liver histopathology and the serum markers of hepatic functional integrity.

Methods

Rats were divided into four main groups: (a) control, (b) CD, (c) TAA and (d) CD?+?TAA. Dietary CD was provoked through the administration of choline-deficient diet, while TAA administration was performed ad libitum through the drinking water (300?mg/l of drinking water).

Results

Histological examination of the CD?+?TAA liver sections revealed micro- and macro-vesicular steatosis with degeneration and primary fibrosis at day 30, to extensive steatosis and fibrosis at day 90. Steatosis was mostly of the macrovesicular type, involving all zones of the lobule, while inflammatory infiltrate consisted of foci of acute and chronic inflammatory cells randomly distributed in the lobule. These changes were accompanied by gradually increasing mitotic activity, as well as by a constantly high alpha-smooth muscle actin immunohistochemical staining. The determination of hepatocellular injury markers such as the serum enzyme levels?? of alanine aminotransferase and aspartate aminotransferase demonstrated a decrease at day 30 (they returned to control levels at days 60 and 90). However, the determination of those serum enzymes used for the assessment of cholestatic liver injury (gamma-glutamyltransferase, alkaline phosphatase) revealed a constant (time-independent) statistically-significant increase versus control values.

Conclusions

Long-term combined dietary CD and TAA administration could be a more realistic experimental approach to human liver diseases involving severe steatosis, fibrosis, stellate cell activation and significant regenerative hepatocellular response.     

Discovery of Novel Alphacoronaviruses in European Rodents and Shrews

Eight hundred and thirteen European rodents and shrews encompassing seven different species were screened for alphacoronaviruses using PCR detection. Novel alphacoronaviruses were detected in the species Rattus norvegicus, Microtus agrestis, Sorex araneus and Myodes glareolus. These, together with the recently described Lucheng virus found in China, form a distinct rodent/shrew-specific clade within the coronavirus phylogeny. Across a highly conserved region of the viral polymerase gene, the new members of this clade were up to 22% dissimilar at the nucleotide level to the previously described Lucheng virus. As such they might represent distinct species of alphacoronaviruses. These data greatly extend our knowledge of wildlife reservoirs of alphacoronaviruses.