Introduction Programmed cell death is well-orchestrated process regulated by multiple pro-apoptotic and anti-apoptotic genes, particularly those of the Bcl-2 gene family. These genes are well documented in cancer with aberrant expression being strongly associated with resistance to chemotherapy and radiation. Areas covered This review focuses on the resistance induced by the Bcl-2 family of anti-apoptotic proteins and current therapeutic interventions currently in preclinical or clinical trials that target this pathway. Major resistance mechanisms that are regulated by Bcl-2 family proteins and potential strategies to circumvent resistance are also examined. Although antisense and gene therapy strategies are used to nullify Bcl-2 family proteins, recent approaches use small molecule inhibitors and peptides. Structural similarity of the Bcl-2 family of proteins greatly favors development of inhibitors that target the BH3 domain, called BH3 mimetics. Expert opinion Strategies to specifically identify and inhibit critical determinants that promote therapy-resistance and tumor progression represent viable approaches for developing effective cancer therapies. From a clinical perspective, pretreatment with novel, potent Bcl-2 inhibitors either alone or in combination with conventional therapies hold significant promise for providing beneficial clinical outcomes. Identifying small molecule inhibitors with broader and higher affinities for inhibiting all of the Bcl-2 pro-survival proteins will facilitate development of superior cancer therapies.

Compared with earlier reports, maternal morbidity and mortality among pregnant women with PAH was reduced, yet maternal complications remain significant and patients should continue to be counseled to avoid pregnancy.

Metastasis is lethal in most bladder cancer patients. Expression of CD24, a glycosyl phosphatidylinositol (GPI)-linked sialoglycoprotein and cancer stem cell marker, is associated with metastatic progression in multiple cancer types, yet the role of CD24 in this process remains unclear. While developing a murine model of human metastatic bladder cancer, we observed that tumor cell CD24 expression correlated with a propensity to metastasize to the lung. Our immunohistochemical evaluation of 60 paired primary and metastatic human bladder cancer samples revealed increased intensity (P < 0.001) and frequency (P < 0.001) of CD24 expression in metastases. To directly evaluate the role of CD24 in metastatic colonization, we manipulated CD24 expression in human bladder cancer cell lines using short hairpin RNA depletion, cDNA overexpression, and fluorescence-activated cell sorting selection. Although suppression of CD24 reduced acute tumor cell retention in the lungs of mice inoculated intravenously with cancer cells, this differential retention was no longer apparent after 24 hours, prompting us to evaluate the role of CD24 in lung colonization. Here, CD24 was found necessary for subsequent development of lung metastases. We next treated clinically detectable lung metastases in mice with anti-CD24 antibody and observed reduced tumor growth and prolonged survival. These findings suggest that CD24 is a lynchpin of metastatic progression and a promising therapeutic target for antimetastatic therapy.

Hypoxia drives malignant progression in part by promoting accumulation of the oncogenic transcription factor HIF-1α in tumor cells. Tumor aggressiveness also relates to elevation of the cancer stem cell-associated membrane protein CD24, which has been causally implicated in tumor formation and metastasis in experimental models. Here we link these two elements by showing that hypoxia induces CD24 expression through a functional hypoxia responsive element (HRE) in the CD24 promoter. HIF-1α overexpression induced CD24 mRNA and protein under normoxic conditions, with this effect traced to a recruitment of endogenous HIF-1α to the CD24 promoter. shRNA mediated-attenuation of HIF-1α or CD24 expression reduced cancer cell survival in vitro and in vivo at the levels of primary and metastatic tumor growth. CD24 overexpression in HIF-1α-depleted cancer cells rescued this decrease while HIF-1α overexpression in CD24-depleted cells did not. Analysis of clinical tumor specimens revealed a correlation between HIF-1α and CD24 levels and an association of their co-expression to decreased patient survival. Our results establish a mechanistic linkage between two critically important molecules in cancer, identifying CD24 as a critical HIF-1α transcriptional target and biological effector, strengthening the rationale to target CD24 for cancer therapy.

Overexpression of CD24, a glycosyl phosphatidylinositol-linked sialoglycoprotein, is associated with poor outcome in urothelial carcinoma and contributes to experimental tumor growth and metastasis. However, the requirement for CD24 ( Cd24a in mice) in tumorigenesis and spontaneous metastasis from the orthotopic site remains uncharacterized. Using N -butyl- N -(4-hydroxybutyl) nitrosamine induction of invasive and metastatic bladder cancer, we show that Cd24a -deficient male mice developed fewer bladder tumors than C57BL/6 control male mice. Evaluating only mice with evidence of primary tumors, we observed that Cd24a- deficient male mice also had fewer metastases than wild-type counterparts. In parallel observations, stratification of patients based on CD24 immunohistochemical expression in their tumors revealed that high levels of CD24 are associated with poor prognosis in males. In female patients and mice the above observations were not present. Given the significant role of CD24 in males, we sought to assess the relationship between androgen and CD24 regulation. We discovered that androgen receptor knockdown in UM-UC-3 and TCCSUP human urothelial carcinoma cell lines resulted in suppression of CD24 expression and cell proliferation. Androgen treatment also led to increased CD24 promoter activity, dependent on the presence of androgen receptor. In vivo, androgen deprivation resulted in reduced growth and CD24 expression of UM-UC-3 xenografts, and the latter was rescued by exogenous CD24 overexpression. These findings demonstrate an important role for CD24 in urothelial tumorigenesis and metastasis in male mice and indicate that CD24 is androgen regulated, providing the foundation for urothelial bladder cancer therapy with antiandrogens.

The expression of human (h) calcitonin (CT) and its receptor (CTR) is localized to basal epithelium in benign prostates but is distributed in whole epithelium of malignant prostates. Moreover, the abundance of hCT and CTR mRNA in primary prostate tumors positively correlates with the tumor grade. We tested the hypothesis that the modulation of endogenous hCT expression of prostate cancer (PC) cell lines alters their oncogenicity. The effect of modulation of hCT expression on oncogenic characteristics was examined in LNCaP and PC-3M cell lines. The endogenous hCT expression was modulated using either constitutively active expression vector containing hCT cDNA or anti-hCT hammerhead ribozymes. The changes in the oncogenicity of cell sublines was assessed with cell proliferation assays, invasion assays, colony formation assays, and in vivo growth in athymic nude mice. Up-regulation of hCT in PC-3M cells and or enforced hCT expression in LNCaP cells dramatically enhanced their oncogenic characteristics. In contrast, the down-regulation of hCT in PC-3M cells led to a dramatic decline in their oncogenicity. These results, when combined with our other results, that the expression of hCT in primary PCs increase with tumor grade, suggest an important role for hCT in the progression of PC to a metastatic phenotype.

In bladder cancer, increased Caveolin-1 (Cav-1) expression and decreased Src expression and kinase activity correlate with tumor aggressiveness. Here, we investigate the clinical and functional significance if any, of this reciprocal expression in bladder cancer metastasis. We evaluated the ability of tumor Cav-1 and Src RNA and protein expression to predict outcome following cystectomy in 257 patients enrolled in two independent clinical studies. In both, high Cav-1 and low Src levels were associated with metastasis development. We overexpressed or depleted Cav-1 and Src protein levels in UMUC-3 and, RT4 human bladder cancer cells and evaluated the effect of this on actin stress fibers, migration using transwells and lung metastasis following tail vein inoculation. Cav-1 depletion or expression of active Src in metastatic UMUC-3 cells decreases actin stress fibers, cell migration and metastasis, while, Cav-1 overexpression or Src depletion increased the migration of non-metastatic RT4 cells. Biochemical studies indicated Cav-1 mediates these effects via its phosphorylated form (pY14), whereas Src effects are mediated through phosphorylation of p190RhoGAP and these pathways converge to reduce activity of RhoA, RhoC and Rho effector ROCK1. Treatment with a ROCK inhibitor reduced UMUC-3 lung metastasis in vivo, phenocopying the effect of Cav-1 depletion or expression of active Src. Src suppresses while Cav-1 promotes metastasis of bladder cancer through a pharmacologically tractable common downstream signaling pathway. Clinical evaluation of personalized therapy to suppress metastasis development based on Cav-1 and Src profiles appears warranted.

Calcitonin (CT) is synthesized and secreted in prostate epithelium, and its secretion from malignant prostates is several-fold higher than from benign prostates. CT receptor (CTR) is expressed in malignant prostate epithelium, and its activation stimulates growth of prostate cancer (PC) cells via activation of adenylyl cyclase and calcium/phospholipid pathways. To identify the role of ''CT System'' in prostate cancer, we tested the expression of CT and CTR mRNAs in invading tumor cells of prostate cancer specimens. The effect of CT on in vitro invasion of PC cell lines and on activation of gelatinases was also examined. The cells of primary tumors and those invading stroma co-expressed CT/CTR mRNAs. Exogenously added CT increased in vitro invasion of PC cell lines and caused a rapid, several-fold but transient increase in protein kinase A activity. In contrast, anti-CT serum caused a dose-dependent inhibition of in vitro invasion of PC-3M cells. CT also increased the concentration and activities of MMP-2 and MMP-9. Rp.cAMP, a competitive inhibitor of cAMP-dependent protein kinase A, myristoylated protein kinase A inhibitory peptide (PKI) as well as the expression of dominant negative form of PKA all attenuated basal in vitro invasion of PC-3M cells, and CT could not increase in vitro invasiveness in their presence. These results suggest that overexpression of ''CT System'' in invasive PC tumors significantly contributes to increased invasiveness of prostate cancer cells. The action of CT may be mediated by protein kinase A signaling, which subsequently leads to increased cell invasion and secretion of gelatinases. ' 2005 Wiley-Liss, Inc.Key words: prostate cancer; invasion; calcitonin; PKA; metastasis Calcitonin (CT), a 32 amino acid peptide produced by C cells of mammalian thyroid, has also been detected in human brain, the pituitary gland, lung carcinoma as well as the conditioned media from the cultures of primary prostate epithelial cells.1-6 Although most well-known functions of CT include inhibition of bone resorption, renal regulation of sodium, phosphate, calcium and neuromodulation, 6 CT has also been shown to regulate secretory and proliferative functions of several organs. [7][8][9] Previous studies from this laboratory have shown that immunoreactive CT (iCT) is secreted by primary prostate epithelial cells, and its secretion from cancer-derived primary prostate cells is several-fold higher than that from the cells of benign prostatic hyperplasia origin. 1 We have reported that mRNAs for CT and its receptor (CTR) are selectively localized to the basal epithelium of benign prostates but are distributed throughout the epithelium of malignant prostates. High-affinity CT receptors have been identified in membrane preparations of primary tumors as well as androgen-responsive LNCaP and highly metastatic but androgen refractory PC-3M prostate cancer cells.10 Exogenously added CT stimulates the proliferation of LNCaP cells by stimulating cAMP accumulation and increasing cytoplasmic Ca 21 transients, and CT al...