Search

In cancer patients detection of systemic disease is of great importance to obtain prognostic information and to guide therapy. Bone marrow (BM) seems to be a common homing tissue for the early spread of tumor cells from various epithelial tumors; however, verification of the prognostic significance of BM-disseminated tumor cells (BM-DTCs), is restricted to breast cancer so far. These cells may be dormant for a long time, and signals triggering their activation leading to recurrence remain to be characterized. A recent study involving metastatic breast cancer patients reported that the shortest disease-free survival is correlated with cytokeratin (CK)-negative BM aspirates and that CK-positive BM-DTCs correspond to dormant tumor cells. Soluble CK fragments in serum including CK18 and 19 (measured as TPS and CYFRA 21-1, respectively) and caspase-cleaved CK18 are widely used to monitor tumor progression and response to therapy, actually indicating proliferation and/or necrotic/apoptotic cell death. In order to assess the source of the CK fragments, we used determinations of CK18 and caspase-cleaved CK18 fragments in serum samples before and after radical tumor surgery in colon cancer patients. Elevated serum concentrations of CK18 were found to persist in patients with a high incidence of BM-DTCs, and high perioperative levels of caspase-cleaved CK18 fragments were detected in patients with early relapses, respectively. These results indicate that in some patients at increased risk of recurrence disseminated cell populations exist that are responsible for the release of the bulk of CK fragments after removal of the apparently nonmetastatic tumor. In good agreement with the results in metastatic breast cancer patients, release of CK18 or 19 fragments by BM-DTCs seem to indicate disseminated tumor cells mainly in a dormant state, whereas caspase-cleaved CK18 may indicate skipping of this latent phase and early progression. Therefore, caspase cleavage of CKs in intact tumor cells seems to accompany or is involved in the differentiation leading from dormant to progressively active disseminated tumor cells. Release of respective CK fragments would result in an apparent clearing of CK-positive cells in BM, leaving malignant cells that have possibly undergone an epithelial-mesenchymal transition. Micrometastatic cancer cell lines derived from breast cancer patients were found to display loss of epithelial CK8, 18 and 19 as well as ectopic expression of vimentin as in mesenchymal cells. In conclusion, degradation of CKs may represent a marker indicating reactivation of dormant tumor cells in BM.

Prostate carcinoma-derived factors induce a proliferative response in osteoblasts. The present study investigated the involvement of MAP kinase in the osteoblastic reaction of osteocytes and the response of 1alpha,25-hydroxy-vitamin D3 (1,25-vitD3)-pretreated osteoblasts. Conditioned media (CM) from prostate, colon, pancreatic, renal cell and breast cancer cell lines were tested on their proliferative activity using murine osteoblast-like MC3T3-E1 cells, MG63 human osteosarcoma cells and immortalized human osteoblasts (AHTO-7). Changes in osteoblastic activities of the supernantants were measured in the presence of MAP kinase inhibitors and following 1,25-vitD3-induced differentiation of the target osteoblasts. Supernatants of prostate cancer cells stimulated proliferation of osteoblasts in all three indicator cell lines, with AHTO-7 exhibiting the most significant correlation to human primary osteoblast cultures. 1,25-vitD3 induced the differentiation marker alkaline phosphatase (ALP) in MC3T3-E1 and AHTO-7, but only to a minor degree in MG63 cells. 1,25-vitD3-induced differentiation reduced the proliferative response to CM from several cell lines in MC3T3-E1 and MG63 to a minor degree, whereas in AHTO-7 cells the osteoblastic reaction was reduced for 2/4 pancreatic, 3/3 colon and 1/1 renal cancer CMs, however not for 3/3 prostate cancer CMs. Stimulation of AHTO-7 cells by CM from prostate cancer lines is inhibited significantly by MEK1 kinase inhibitor PD 98059 in contrast to CMs derived from other carcinomas, except ACHN renal cancer cells. The findings in the present study demonstrate that human AHTO-7 cells seem to represent a valid human system to monitor osteoblastic activity, especially in respect to 1,25-vitD3-induced differentiation. Vitamin D3-induced differentiation has no direct effect on prostate cancer-derived osteoblastic activity in the same cell line in vitro, which however, could be reversed by disruption of the signal transduction at the MAP kinase level, revealing a new target for the inhibition of prostate cancer-associated bone formation.

10-hydroxycamptothecin (HCPT), a natural analog of the alkaloid camptothecin (CPT), is a promising anticancer agent currently undergoing preclinical trials. Though HCPT is less toxic and more active in various human cancer cell lines and in animal tumor models than the clinically approved CPT-analog topotecan, little is known about its biotransformation products and their route of elimination. To investigate the metabolism and biliary excretion, livers of male Wistar rats were perfused with HCPT (5 microM). Bile and perfusate samples were collected for 60 min and quantified by reversed-phase high-performance liquid chromatography (HPLC). Besides HCPT, three metabolites, namely HCPT glucuronide (M1), hydroxyHCPT glucuronide (M2), and hydroxyHCPT (M3) could be identified by enzymatic hydrolysis with beta-glucuronidase and mass spectroscopy. Biliary secretion of HCPT and M1-M3 reached a peak secretion of 1532+/-124, 75+/-16, 5.8+/-1.6 and 2.1+/-0.5 pmoles/g liver.min, respectively, after 25 min. The total amount of HCPT and M1-M3 excreted into bile during the time of perfusion (60 min) was low and represented a mean of 9.9+/-3.2%, 0.44+/-0.17%, 0.041+/-0.010%, and 0.022+/-0.004% of the initial HCPT dose, respectively. In the perfusate, besides HCPT M1 and M2 but not M3 could be detected (maximum concentrations after about 20 min: 3248+/-210, 16.8+/-2.8 and 1.0+/-0.4 pmoles/g liver.min, respectively). The cumulative efflux of HCPT and M1 and M2 into the perfusate was 21.1+/-3.9%, 0.145+/-0.036% and 0.018+/-0.004% of the initial dose, respectively, indicating a preferable non-biliary secretion for HCPT and a predominant biliary elimination for conjugated HCPT biotransformation products. In conclusion, HCPT is biotransformed in a rat liver model to three metabolites, mainly excreted into bile, which may be of clinical relevance during cancer therapy.

Based on the fact that somatostatin (SST) analogs have given promising results for treatment of hepatocellular cancer, we performed both in vitro and in vivo investigations to define the role of a depot formulation of the long acting SST-analog lanreotide (LAN). A decrease of cells in the S-phase as compared to controls (p

Resveratrol, a natural phytoestrogen, has been reported to promote differentiation of murine MC3T3-E1 osteoblasts and to inhibit proliferation of prostate cancer cell lines. In the present study we tested the effects of resveratrol on the increased proliferation of human AHTO-7 osteoblastic cell line induced by conditioned media (CM) from a panel of carcinoma cell lines. This compound was found to modulate AHTO-7 proliferation in a tamoxifen-sensitive mechanism at lower concentrations, but failed to induce the osteoblast differentiation marker alkaline phosphatase (ALP) in contrast to vitamin D3. The proliferative response of AHTO-7 cells to conditioned media from carcinoma cell lines was diminished (30-71.4% inhibition) upon pretreatment with 0.5 microM resveratrol. Highest inhibition was demonstrated for pancreas (BxPC3, Panc-1), breast (ZR75-1) and renal (ACHN) carcinoma cell line supernatants whereas the effect on colon carcinoma (SW620, Colo320DM) cell CM and prostate cancer (PC3, DU145 and LNCaP) CM was less pronounced. Direct addition of resveratrol affected only supernatants of cell lines (