Naseema Hoosein

Differential Effects of Peptide Hormones Bombesin, Vasoactive Intestinal Polypeptide and Somatostatin Analog RC-160 on the Invasive Capacity of Human Prostatic Carcinoma Cells

The effects of bombesin, vasoactive intestinal polypeptide (VIP), and a somatostatin analog (RC-160) on the in vitro invasion of reconstituted basement membrane (Matrigel) by two human prostatic carcinoma cell lines were examined. Aggressively growing PC-3 cells were found to be invasive in this assay in contrast to the relatively indolent LNCaP cells. Bombesin increased penetration of basement membrane by both cell lines. Although VIP had no effect on invasion by PC-3 cells, it enhanced invasion by LNCaP cells in a dose-dependent manner. In agreement with these results, VIP stimulated adenylate cyclase activity only in LNCaP cells. In contrast to bombesin and VIP, RC-160 did not alter invasion by either cell line. Our results suggest that certain neuroendocrine peptides can increase the invasive potential of prostatic carcinoma cells and may thereby contribute to the rapid progression and aggressive clinical course of prostate tumors containing neuroendocrine elements.

Involvement of urokinase and its receptor in the invasiveness of human prostatic carcinoma cell lines

We have investigated the role of urokinase (UK) and its cell-surface receptor in determining the invasiveness of prostate cancer cells. Three human cell lines, DU-145, PC-3 and LNCaP, that differ in androgen-responsiveness and growth characteristics, were tested. Analysis of the conditioned medium by an enzyme-linked immunosorbent assay showed secretion of UK by DU-145 (63 ng/mL/10(6) cells/48 hr) and PC-3 (682 ng/mL/10(6) cells/48 hr), but absence of secretion by LNCaP cells. Western blot analysis and enzyme activity assay of the conditioned medium confirmed these results. Scatchard analysis of radioligand binding with acid pretreated cells showed the presence of a single population of high affinity UK receptors on DU-145 cells (93,000 sites/cell, Kd = 0.9 nM) and PC-3 cells (25,000 sites/cell, Kd = 1.0 nM) but not on LNCaP cells. DU-145 and PC-3 cells were found to be highly invasive in in vitro invasion assays: 4.5 +/- 0.5% and 6.5 +/- 0.5%, respectively, of total tumor cells (approximately 2 x 10(5)) had penetrated reconstituted basement membrane (Matrigel) in a 72 hr incubation in serum-free growth medium. Under similar conditions, less than 0.25% LNCaP cells invaded Matrigel. The data indicate that androgen unresponsive, aggressive prostate tumor cells of high metastatic potential, DU-145 and PC-3, secrete UK and display cell-surface UK receptors, fully charged with the protease. Conversely, relatively indolent LNCaP cells of low metastatic potential do not secrete UK nor do they possess its binding sites. UK receptor antagonists, UK 12-32 and UK 6-135, which compete with labeled UK for binding to prostatic cells but do not inhibit cellular proliferation or UK secretion, markedly reduced DU-145 and PC-3 cell invasion (80-85% inhibition), thereby suggesting an important role of receptor-bound UK in prostate tumor cell invasion.

Growth-Inhibitory Effects of Serotonin Uptake Inhibitors on Human Prostate Carcinoma Cell Lines

Growth stimulation of a variety of cell types by the neurotransmitter serotonin has been reported. We have examined the effects of three serotonin-uptake inhibitors, 6-nitroquipazine, zimelidine and fluoxetine (Prozac, Eli Lilly Co., Indianapolis, Indiana) on human prostate carcinoma cell lines. In vitro, all 3 of these compounds inhibited the proliferation of PC-3, DU-145 and LNCaP cells in a dose-dependent manner. Also, all 3 compounds blocked the uptake of a radiolabeled analog of serotonin by the prostate carcinoma cell lines. The order of potency for inhibition of growth as well as for serotonin uptake was fluoxetine > zimelidine > 6-nitroquipazine. The growth of subcutaneous, PC-3 xenografts in athymic nude mice was significantly inhibited by fluoxetine. These results implicate biogenic amines such as serotonin in the growth of prostate carcinoma cells and indicate the potential use of serotonin-uptake inhibitors for the treatment of prostate cancer.

Clinical significance of elevation in neuroendocrine factors and interleukin-6 in metastatic prostate cancer

Serum biomarkers that reflect the complex pathways of cancer progression have contributed to the clinical understanding of many malignancies. Recent studies have suggested that certain neuroendocrine (NE) elements participate in prostate cancer (PCa) progression. Interleukin-6 (IL-6) may serve as a useful marker of and contribute to PCa morbidity. The purpose of this study was to assess the frequency of elevation of two NE factors, chromogranin A (CGA) and bombesin-like immunoreactivity (BLI), in patients with advanced PCa and to determine their relationship to serum prostate-specific antigen PSA) and IL-6 levels, as well as known prognostic indicators (hormonal state, stage). Serum CGA determined by radioimmunoassay was elevated in I (7%) of 15 androgen-dependent (AD) patients and II (52%) of 21 androgen-independent (AI) patients; and urine BLI determined by radioimmunoassay was elevated in 2 (13%) of 16 AD patients and 10 (39%) of 21 AI patients. Frequency of elevation was higher in patients with distant metastasis (bone, visceral) compared with those with local/regional extensions of the disease. Levels of the NE factors correlated well with serum and bone marrow aspirate IL-6 concentrations but not with serum PSA levels. Elevation in either NE factor predicted for shortened survival. Measurement of NE factors in PCa identifies a subset of patients with advanced disease likely to express high levels of IL-6 and have a shorter survival. If confirmed, these findings will support the existence of a clinically relevant subset of patients in whom NE factors are involved in AI PCA progression.

Modulation of neuroendocrine differentiation in prostate cancer by interleukin‐1 and ‐2

Neuroendocrine differentiation in prostate cancer has received much attention recently because it has been found to be associated with androgen independence and shortened patient survival in some studies. We have investigated the effect of the cytokines interleukin‐1 (IL‐1), IL‐2, and IL‐6 on the expression of the neuroendocrine marker chromogranin A in human prostate cancer cell lines. Chromogranin A was measured by fluorescence‐immunoassay, as well as by immunoblotting. We find that IL‐1β and IL‐6 increase the cellular content and chromogranin A secretion by LNCaP and DU‐145 cells. By contrast, IL‐2 decreases the cellular and secreted chromogranin A levels in the two cell lines. Our results suggest that these proinflammatory cytokines can influence neuroendocrine differentiation in prostate cancer and be involved in disease progression. Prostate Supplement 8:32–36, 1998.

Changes in beta-2 microglobulin expression in prostate cancer

Increased shedding of beta-2 microglobulin (B2m, 11.8 kDa), a component of the major histocompatibility complex class I (MHC I), by tumor cells has significance with regard to escape from immune-surveillance, cellular proliferation, and tumor development and progression. Aberrant expression of MHC I is known to occur in prostate cancer (PCa) but not in benign prostatic hyperplasia. We have determined B2m released by PCa cells in culture and in the urine of 101 patients with advanced PCa by Western blotting and radioimmunoassay. B2m levels in the conditioned medium of human PCa cell lines and primary cultures derived from distant metastasis as well as in the urine of patients with bone and visceral metastasis were higher than normal and also higher than those from patients with local/regional extensions of the disease. In the group of patients with bone metastasis (66 patients), high urine B2m was associated with significantly shortened survival. In addition to the 11.8 kDa B2m, a high molecular weight B2m immunoreactivity of approximately 38 kDa was found in highly tumorigenic PC-3 cell line, but not in the relatively indolent DU-145 and LNCaP human PCa cell lines. The approximately 38 kDa B2m was found in the urine of several PCa patients but not of healthy controls examined by Western analysis. The conditioned medium of a prostatic small cell carcinoma cell line, NCI-H660, had high levels of chromogranin A and B2m, but prostate specific antigen was absent. In conclusion, increased B2m shedding was associated with distant metastasis of PCa and an abnormal B2m immunoreactivity was found in PCa.

Differences in the expression and effects of interleukin-1 and -2 on androgen-sensitive and -insensitive human prostate cancer cell lines

The presence of interleukin-1 (IL-1) and IL-2 mRNA in five human prostate cancer (PCa) cell lines and their effects on cellular proliferation and prostate-specific antigen (PSA) levels were examined. IL-1 was found in androgen-unresponsive PC-3 and DU-145 but not in the androgen-responsive LNCaP, MDA-PCA-2a and MDA-PCA-2b cell lines. IL-2 message was absent while that of GAPDH (positive control) was present in all five cell lines. IL-1 decreased while IL-2 increased PSA levels of near-confluent LNCaP cells after 24 h of treatment. IL-1 inhibited whereas IL-2 stimulated the growth of sub-confluent LNCaP cells (72 h). Neither cytokine affected the proliferation of DU-145 or PC-3 cells.

Secretion of prostate-specific antigen-suppressing activity by two human prostate carcinoma cell lines

The well-differentiated human prostatic carcinoma cell line LNCaP has often been used as a model to study the modulation of prostate-specific antigen (PSA) expression. In this study, we examined the effect of conditioned medium from two androgen-unresponsive, PSA-negative human prostatic carcinoma cell lines, PC-3 and DU-145, on PSA expression by the LNCaP cells. Our results show, for the first time, that the undifferentiated PC-3 and DU-145 cells secrete a factor that lowers PSA mRNA and protein levels in LNCaP cells. Further characterization of the PSA-suppressing activity indicated that it was trypsin as well as acid sensitive, heat-stable, and ammonium sulfate precipitable. The activity was present in the 30-100-kd fraction of PC-3 and DU-145 conditioned media. This PSA-suppression factor could act in an autocrine manner to render undifferentiated prostatic carcinoma cells PSA negative. It may also be responsible for the lack of increase in serum PSA levels observed in a subset of patients with hormone-resistant prostatic carcinoma.