33 research outputs found
Transplantable human prostate cancer (PC-82) in athymic nude mice : a model for the study of androgen-regulated tumor growth
This thesis describes the characterization and further application of a model system for
prostate cancer, the human prostatic adenocarcinoma PC-82 which is transplantable in
athymic nude mice.
The mortality rate of patients suffering from prostatic carcinoma is high, in spite of the
high response rates which are initially achieved with hormonal treatment ofthese patients.
Growth and function of the prostate are primarily dependent on androgenic stimuli.
Hormonal treatment of prostatic carcinoma is based upon the suppression of the testicular
production of androgens. This can be achieved directly by surgical removal of the testes or
indirectly by inhibiting the hypophyseal gonadotropin release through treatment with
estrogens or analogues of luteinizing hormone-releasing hormone (LHRH). However, in
the majority of patients relapse of the tumor occurs following a favorable response to
androgen-ablation therapy. Progression is caused mainly by a loss of androgen-sensitivity of
the tumor.
Since many investigations relevant to prostate cancer cannot be performed in patients,
there is a great need for well-characterized model systems which reflect the properties of
clinical prostate cancer. Relevant aspects of the prostate in general and of prostatic
carcinoma in particular are described in chapter 1, which also contains a summary of the
current knowledge of androgen action in the prostate and information on the available
model systems for prostatic cancer
The human prostatic cancer cell line LNCaP and its derived sublines: An in vitro model for the study of androgen sensitivity
__Abstract_
The LNCaP-FGC (fast growing colony) cell line, a subline derived from the LNCaP cell line, shares all the main characteristics, including its androgen sensitivity, described for the parental line. A number of sublines originating from the FGC line were characterized with respect to their response to steroid-depleted medium and to the synthetic androgen R1881. The growth of FGC cells in DCC medium with 0.1 nM R1881 was stimulated 2â3-fold compared to growth in DCC medium only. FGC cells that were continuously grown in DCC medium did not die, but their growth rate was clearly slowed down, and the cells remained responsive to androgen. These cells, therefore, have the androgen-sensitive, rather than the androgen-dependent phenotype. As cells of the subline FGC-JB could not be maintained in DCC medium, these cells better represent the androgen-dependent cell type. In contrast to the FGC line, cells of the R line, grew equally well in medium with complete or DCC serum. Under none of these culture conditions, R cells could significantly be stimulated further with R1881. Further analysis of the LNCaP-FGC sublines should provide valuable information concerning the development of androgen resistance in human prostate cancer
Neuroendocrine cells in the normal, hyperplastic and neoplastic prostate
Neuroendocrine cells can be demonstrated in normal, hyperplastic and neoplastic prostatic tissues. The products secreted by these cells can be used as tissue and/or serum markers but may also have biological effects. Neuroendocrine cells in prostate cancer most probably do not contain the androgen receptor and are therefore primarily androgen independent. Some of the neuropeptides secreted by the neuroendocrine cells may act as growth factor by activation of membrane receptors in an autocrine-paracrine fashion or by ligand-independent activation of the androgen receptor in neighboring non-neuroendocrine cells. Evidence is accumulating from experiments with tumor models that neuropeptides indeed can influence the growth of prostatic tumor cells. Future research on neuroendocrine differentiation may answer some questions concerning the biological behavior of clinical prostatic tumors
Determination of Ki-67 defined growth fraction by monoclonal antibody MIB- I in formalin-fixed, paraffin-embedded prostatic cancer tissues
The applicability of MIBâ1, a monoclonal antibody directed against the Kiâ67 antigen, was studied in the PCâ82 and LNCaP prostatic tumor models at various levels of proliferative activity. Statistically significant correlations were found in LNCaP cultures between Kiâ67 and MIBâ1 scores (r = 0.84, P < 0.001), and in PCâ82 tumors between MIBâ1 scores and paraffin tissue Kiâ67 (pKiâ67) (r = 0.90, P < 0.001), frozen tissue Kiâ67 (fKiâ67) (r = 0.86, P < 0.001), and BrdU uptake (r = 0.70, P < 0.001), respectively. pKiâ67 scores were double the fKiâ67 scores, which may be due to methodological differences. MIBâ1 scores exceeded both the fKiâ67 and pKiâ67 scores. The affinity of MIBâ1 for the antigen is much higher than the affinity of Kiâ67, which may explain the differences. MIBâ1 is a promising means of evaluating the presence of only minute amounts of the Kiâ67 antigen in paraffinâembedded human tumor material, especially in relatively slowly growing tumors
Effects of low testosterone levels and of adrenal androgens on growth of prostate tumor models in nude mice
Abstract
Two transplantable, androgen dependent prostate tumor models of human origin, PC-82 and PC-EW, were used to study the effect of low androgen levels and adrenal androgens on prostate tumor cell proliferation. Tumor load of the PC-82 and PC-EW tumors could be maintained constant when plasma testosterone levels were 0.8 and 0.9 nmol/l, respectively, corresponding with an intratissue 5α-dihydrotestosterone level of 3â4 pmol/g tissue. This critical androgen level for prostate tumor growth stimulation amounted to 2â3 times the castration level and proved to be similar for both tumor models. Relatively high levels of androstenedione resulted in physiological levels of plasma testosterone causing androgen concentrations in PC-82 tumor tissue exceeding the critical level for tumor growth. These results indicate that submaximal suppression of androgens can stop tumor growth in these prostate tumor models
Kinetics of neuroendocrine differentiation in an androgen-dependent human prostate xenograft model
It was previously shown in the PC-295 xenograft that the number of
chromogranin A (CgA)-positive neuroendocrine (NE) cells increased after
androgen withdrawal. NE cells did not proliferate and differentiated from
G0-phase-arrested cells. Here we further characterized NE differentiation,
androgen receptor status, and apoptosis-associated Bcl-2 expression in the
PC-295 model after androgen withdrawal to assess the origin of NE cells.
PC-295 tumor volumes decreased by 50% in 4 days. Intraperitoneal
bromodeoxyuridine (BrdU) incorporation and MIB-1 labeling decreased to 0%,
and the apoptosis was maximal at day 4. Androgen receptor expression and
prostate-specific antigen (PSA) serum levels decreased rapidly within 2
days. The number of NE cells increased 6-fold at day 4 and 30-fold at day
7. Five and ten percent of the CgA-positive cells were BrdU positive after
continuous BrdU labeling for 2 and 4 days, respectively. However, no MIB-1
expression was observed in CgA-positive cells. NE cells expressed the
regulated secretory pathway marker secretogranin III but were negative for
androgen receptor and Bcl-2. Bcl-2 expression did increase in the non-NE
tumor cells. In conclusion, androgen withdrawal leads to a rapid PC-295
tumor regression and a proliferation-independent induction of NE
differentiation. The strictly androgen-independent NE cells that were
still present after 21 days differentiated mainly from G0-phase-arrested
cells
MIB-1 (KI-67) proliferation index and cyclin-dependent kinase inhibitor p27(Kip1) protein expression in nephroblastoma
PURPOSE: A number of studies have indicated that the tumor proliferation
marker MIB-1 and cell cycle inhibitor p27(Kip1) expression are of
prognostic importance in a variety of cancers. The present study was
performed to evaluate the prognostic value of these molecules in Wilms'
tumors. EXPERIMENTAL DESIGN: MIB-1 and p27(Kip1) expressions were
investigated by the means of immunohistochemical analysis of 62 Wilms'
tumor. Patients were preoperatively treated by chemotherapeutic agents and
had a mean follow-up of 5.7 years. RESULTS: MIB-1 and p27(Kip1) were
expressed in normal kidney tissues and in the three main components of
Wilms' tumor, i.e., the blastemal, epithelial, and stromal cells. In
Wilms' tumors, the percentage of MIB-1-positive cells in the blastema
ranged between 0 and 42% (mean, 9.4%) and in the epithelial component
between 0 and 53% (mean, 19.9%), with a significant difference (P < 0.01).
The percentage of blastemal p27(Kip1)-positive cells ranged between 3 and
85% (mean, 55.1%) and for the epithelial component between 1 and 87%
(mean, 59%). There was a significant inverse relationship between
blastemal MIB-1 and p27(Kip1) expression in Wilms' tumor. Univariate
analysis showed that blastemal MIB-1 and p27(Kip1) expression were
indicative for clinical progression and tumor-specific survival. In a
multivariate analysis, blastemal MIB-1 and p27(Kip1) protein expression
proved to be an independent prognostic for clinical progression besides
stage. CONCLUSIONS: It was concluded that both MIB-1-based proliferative
activity and p27(Kip1) protein expression in the blastema have prognostic
impact in Wilms' tumor
Characterization of a zinc-finger protein and its association with apoptosis in prostate cancer cells
BACKGROUND: The transition from androgen-dependent to androgen-independent
prostate cancer is not fully understood but appears to involve multiple
genetic changes. We have identified a gene, GC79, that is more highly
expressed in androgen-dependent LNCaP-FGC human prostate cancer cells than
in androgen-independent LNCaP-LNO human prostate cancer cells. Physiologic
levels (0.1 nM:) of androgens repress expression of GC79 messenger RNA
(mRNA) in LNCaP-FGC cells. To determine the role of GC79, we cloned its
complementary DNA (cDNA) and functionally characterized its product.
METHODS: The differentially expressed GC79 gene was cloned from human
prostate cDNA libraries, sequenced, and transfected into mammalian cells
to study its function. Expression of GC79 was analyzed in various adult
and fetal human tissues and in prostate glands of castrated rats. The
association of GC79 expression and apoptosis was investigated in COS-1 and
LNCaP cells transfected with GC79 cDNA. All statistical tests are
two-sided. RESULTS: Sequence analysis indicates that GC79 encodes a large,
complex, multitype zinc-finger protein, containing nine C(2)H(2)-type
zinc-finger domains, a cysteine-rich region, and a GATA C(4)-type
zinc-finger domain. Castration-induced androgen withdrawal increased the
expression of GC79 mRNA in the regressing rat ventral prostate, suggesting
that the expression of GC79 mRNA is associated with the process of
apoptotic cell death in the rat ventral prostate. Transfection and
induction of GC79 cDNA in both COS-1 and LNCaP prostate cancer cells led
to an apoptotic index that was eightfold higher (P:<.001, two-sided
Student's t test) than that observed in uninduced transfected cells.
CONCLUSIONS: We have cloned an androgen-repressible gene, GC79, that is
potentially involved in apoptosis. This finding may have implications for
the development of androgen-independent prostate cancer and, ultimately,
for the treatment of prostate cancer