Multipathways for transdifferentiation of human prostate cancer cells into neuroendocrine-like phenotype

Abstract

The neuroendocrine (NE) cell is a minor cell population in normal human prostate glands. The number of NE cells is increased in advanced hormone-refractory prostate carcinomas (PCA). The mechanism of increased NE cell population in these advanced tumors is poorly understood. We examined molecular mechanisms which may be involved in the regulation of the transdifferentiation process of human PCA cells leading to a NE phenotype. We compared PCA cell lines LNCaP and PC-3 in the following medium conditions: steroid-reduced (SR), interleukin-6 (IL-6)-supplemented, or dibutyrate cAMP (db-cAMP)-supplemented. We found that androgen-responsive C-33 LNCaP cells responded to all treatments, having a neuronal-like morphology. In contrast, C-81 LNCaP cells, having a decreased androgen responsiveness, had a less pronounced effect although followed a similar trend. Androgen-unresponsive PC-3 cells showed little change in their morphology. Grown in the SR condition, the level of neuron-specific enolase (NSE), a marker of neuronal cells, was upregulated in C-33 LNCaP cells, while to a lesser degree in the presence of IL-6. In the presence of db-cAMP, the NSE level in C-33 cells was decreased, lower than that in control cells. An opposite effect was observed for C-81 LNCaP cells. Nevertheless, the NSE level was only elevated in db-cAMP-treated PC-3 cells, but no change was found in PC-3 cells grown in the SR- or IL-6-supplemented medium. Thus, a similar gross phenotypic change may correlate with differential molecular expressions. We also analyzed the expression of protein tyrosine phosphatase alpha (RPTPalpha) since it plays a critical role in normal neuronal differentiation and signaling. Our results showed that the expression of RPTPalpha correlates with the NE phenotypic change of LNCaP cells in the SR condition. In summary, our data clearly show that the molecular process by which cultured human prostate cancer cells undergo a transdifferentiation process to a NE cell-like phenotype is accompanied by differential expressions of different markers, and a gross NE cell-like phenotype can occur by exposing PCA cells to different pharmacological agents.

Neuroendocrine-like prostate cancer cells: neuroendocrine transdifferentiation of prostate adenocarcinoma cells

“…The initial study revealed that androgensensitive (AS) LNCaP cells exhibit the capability of being transdifferentiated into an NE-like phenotype in response to androgen deprivation (Shen et al 1997). Our data further showed that androgenreduced media can induce NE transdifferentiation of AS LNCaP cells, and these cells acquire the neuronal phenotype and express multiple NE markers, including NSE, CgA, gastrin, and neurotensin (Zelivianski et al 2001, Yuan et al 2006. This NE transdifferentiation induced by steroidreduced (SR) medium is reversed by the addition of DHT.…”

“…In addition to the regulation of integrin signaling and potassium channel activity, RPTPa plays a critical role in neuronal differentiation (Pallen 2003). In AS LNCaP cells, the expression of RPTPa at both mRNA and protein levels is upregulated by androgen depletion, correlating with NE differentiation and NSE expression (Zelivianski et al 2000(Zelivianski et al , 2001. Furthermore, addition of androgens abolishes steroid depletion-induced RPTPa elevation, while Casodex can compete out androgen effects and restores RPTPa as well as NSE expression (Zhang et al 2003).…”

Overexpression of an α1H (Cav3.2) T-type Calcium Channel during Neuroendocrine Differentiation of Human Prostate Cancer Cells

“…Physiological Implication of Voltage-dependent Calcium Channels-To identify the putative involvement of T-type calcium channels in prostate cell physiology, we first studied the influence, on voltage-dependent calcium currents, of steroid reduction, previously reported to induce neuroendocrine differentiation (10,11). Indeed, LNCaP cells cultured in steroidreduced conditions displayed a morphological differentiation as shown on Fig.…”

“…The stimulation of neuroendocrine differentiation by interleukin 6 has been shown to involve the induction of cyclin-dependent kinase inhibitor p27 Kip1 (7), as well as the tyrosine phosphorylation of epithelial and endothelial tyrosine kinase Etk/ Bmx through the activation of phosphatidylinositol 3Ј-kinase (6). Steroid removal from the culture medium was also shown to induce neuroendocrine differentiation (10,11).…”

Androgen signaling and post-transcriptional downregulation of Bcl-2 in androgen-unresponsive prostate cancer

“…The NE-like LNCaP cells grown under steroid-reduced conditions have been shown to express androgen receptor. 16 It was possible to reverse the NElike phenotype after 1 month by changing the media to normal serum. However, beyond 3 months in media containing charcoal-stripped serum, the cell morphology could not be reversed.…”