Allelic losses in localized prostate cancer: association with prognostic factors

Detection of Loss of Heterozygosity (LOH) Using Circulating Cell-free DNA (cfDNA) by Fluorescence-based Multiplex PCR for Identification of Patients With Prostate Cancer

Several lines of evidence suggest that loss of heterozygosity (LOH) in specific chromosomal regions is a common mechanism for the inactivation of tumor-suppressor genes that are implicated in the pathogenesis of prostate cancer (PCa). Short tandem repeat (STR) sequences are extremely reliable genetic markers for the detection of LOH associated with cancers. Hence, in the current study, we investigated the detection of LOH at 6 STR markers (D8S360, D9S1748, D9S171, D8S137, D6S1631, and THRB) using blood circulating cell-free DNA (cfDNA), which can be used to distinguish PCa from benign prostatic hyperplasia (BPH). A total of 136 individuals were included in the study, 76 male patients diagnosed with PCa (50 male patients with localized PCa and 26 male patients with metastatic PCa) as experimental subjects and 60 male patients with BPH as controls. Circulating cfDNA was extracted from plasma samples and amplified with fluorescence-labeled primers specific for known STR markers. We also evaluated the serum prostate-specific antigen in both groups. Our findings revealed that the frequency of LOH at D8S360, D9S1748, D9S171, D8S137, and D6S1631 was significantly higher in PCa subjects than in controls (P<0.05). Of the 6 STR markers, LOH at D8S360 could discriminate metastatic PCa from localized PCa. We found that 71.05% of patients with PCa and 1.66% of BPH subjects had LOH at least at 3 of the markers in cfDNA. Our findings provide additional evidence to support the hypothesis that analysis of LOH at D8S360, D9S1748, D9S171, D8S137, and D6S1631 STR markers using cfDNA can be applied as a noninvasive diagnostic approach for the detection of PCa.

MTUS1, a gene encoding angiotensin-II type 2 (AT2) receptor-interacting proteins, in health and disease, with special emphasis on its role in carcinogenesis

Loss of tumor suppressor activity is a frequent event in the formation and progression of tumors and has been listed as an important hallmark of cancers. Microtubule-Associated Scaffold Protein 1 (MTUS1) is a candidate tumor suppressor gene which is reported to be frequently down-regulated in a variety of human cancers including pancreas, colon, bladder, head-and-neck, ovarian, breast cancers, gastric, lung cancers. It is also reported to be implicated in several types of pathologies such as cardiac hypertrophy, atherosclerosis, and SLE-like lymphoproliferative diseases. Moreover, MTUS1-encoded proteins are shown to be involved in the regulation of vital cellular processes such as proliferation, differentiation, DNA repair, inflammation, vascular remodeling and senescence. However, the current knowledge is very limited about the role of this gene in human cancers as well as other type diseases. Besides, there is no literature report which summarizes and criticizes the importance of MTUS1 in the cellular processes, especially in the processes of carcinogenesis. Accordingly, in this comprehensive review, we tried to shed light on the role of tumor suppressor MTUS1/ATIP in health and disease, putting special emphasis on its role in the development and progression of human cancers as well as associated molecular mechanisms and the reasons behind MTUS1/ATIP deficiency, which have been not well documented previously.

Inhibitor of growth-4 mediates chromatin modification and has a suppressive effect on tumorigenesis and innate immunity

Inhibitor of growth-4 (ING4) is a member of the ING family and acts as a tumor suppressor protein. ING4 is a promising candidate for cancer research due to its anti-angiogenic function and its role in the inhibition of cell migration, cell cycle, and induction of apoptosis. Interaction of this protein with the histone acetyl transferase complex plays a vital role in the regulation of multiple nuclear factor kappa light chain enhancer of activated B cells response elements and thus in the regulation of innate immunity. Splice variants of ING4 have different binding affinities to target sites, which results in the enhancement of its functional diversity. ING4 is among the few known regulatory proteins that can directly interact with chromatin as well as with transcription factors. The influence of ING4 on tumor necrosis factor-α, keratinocyte chemoattractant, interleukin (IL)-6, IL-8, matrix metalloproteinases, cyclooxygenase-2, and IκBα expression clearly demonstrates its critical role in the regulation of inflammatory mediators. Its interaction with liprin α1 and p53 contribute to mitigate cell spreading and induce apoptosis of cancer cells. Multiple factors including breast cancer melanoma suppressor-1 are upstream regulators of ING4 and are frequently deactivated in tumor cells. In the present review, the different properties of ING4 are discussed, and its activities are correlated with different aspects of cell physiology. Special emphasis is placed on our current understanding of ING4 with respect to its influence on chromatin modification, tumorigenesis, and innate immunity.

Apoptosis regulators Fau and Bcl-G are down-regulated in prostate cancer

BACKGROUND

The molecular control of cell death through apoptosis is compromised in prostate cancer cells, resulting in inappropriate cell survival and resistance to cytotoxic therapy. Reduced expression of the functionally connected apoptosis-regulators and candidate tumor suppressors Fau and Bcl-G has recently been implicated in oncogenesis in other tissues. The present study examines the hypothesis that reduced expression of these genes may be involved in prostate cancer.

METHODS

Fau and Bcl-G mRNA levels were determined by real time RT-PCR in two independent prostate tissue collections. In experiments in vitro, Fau and Bcl-G levels in prostate cancer cell lines were reduced using RNA interference and the effects on sensitivity to UVC irradiation were determined.

RESULTS

Fau and Bcl-G mRNA levels were both lower in prostate cancer tissue than in normal prostate and Benign Prostate Hyperplasia. Active down-regulation of Fau and Bcl-G expression in vitro resulted in decreased sensitivity to UVC-induced cytotoxicity. Simultaneous down-regulation of Fau and Bcl-G produced a decrease in sensitivity which was similar to either gene alone.

CONCLUSIONS

Fau and Bcl-G mRNA levels are both decreased in prostate cancer. In prostate cancer cell lines in vitro such down-regulation results in reduced sensitivity to UVC-induced cytotoxicity, consistent with the putative roles of these genes as candidate prostate tumor suppressors. The absence of an additive effect when Fau and Bcl-G were down-regulated simultaneously is consistent with the two genes acting in the same apoptosis pathway, for example, with the pro-apoptotic effects of Fau being mediated through modulation of Bcl-G.

BCAR1 expression in prostate cancer: association with 16q23 LOH status, tumor progression and EGFR/KAI1 staining

BACKGROUND

The 16q23 locus has been recently suggested in both breast and prostate cancer to contain a gene involved in disease progression. The breast cancer antiestrogen resistance 1 (BCAR1) gene, located at 16q23, contributes to many cellular processes including migration and survival, and interacts in vitro with the growth factor receptor EGFR and the metastasis suppressor KAI1.

METHODS

BCAR1, EGFR, and KAI1 expression was studied by immunohistochemistry on a tissue microarray containing 100 localized prostate cancers (LPC), 15 hormone refractory prostate cancers (HRPC), and 15 lymph node metastasis (LNM). Forty eight of the LPC were also analyzed for 16q23 LOH status using microsatellite markers.

RESULTS

BCAR1 staining was present in 25% of LPC, associated with higher Gleason score, and in 60% and 80% of, respectively, LNM and HRPC. BCAR1 expression was inversely correlated with 16q23 LOH status (P < 0.001), and was associated with high EGFR staining (P < 0.02), and negative KAI1 expression (P < 0.01).

CONCLUSIONS

BCAR1 expression in LPC seems to be regulated at least in part by genetic events. The increased expression of BCAR1 with disease progression suggests a potential interest for both prognosis and treatment.

Comparison of Genetic Alterations Detected in Circulating Microsatellite DNA in Blood Plasma Samples of Patients with Prostate Cancer and Benign Prostatic Hyperplasia

Prostate cancer is the most frequent malignant disease and the second most frequent cause of death due to cancer in men in the Western world. Since serum prostate-specific antigen (PSA) and its subforms show poor specificity in clinical practice, a molecular marker for the detection and discrimination of prostate cancer (PCa) could be of great interest. To investigate the potential significance of genetic aberrations, such as loss of heterozygosity (LOH), in PCa we identified and characterized allelic losses in circulating tumor-associated DNA in blood from patients with localized PCa. Genomic DNA extracted from cell-free plasma of blood samples drawn from 65 PCa patients was analyzed using a panel of 15 polymorphic microsatellite markers mapping to known tumor-suppressor genes. Comparative analyses were performed with a control group of 36 patients with benign prostatic hyperplasia (BPH). In the current study, we demonstrate that PCa patients had higher DNA concentrations in their blood circulation than BPH patients. In the marker panel studied, LOH was more frequently detected in PCa patients (34%) than in BPH patients (22%). The incidence of LOH in the plasma DNA of PCa patients was highest at chromosomal regions 3p24 (THRB, 22%) and 8p21 (D8S360, 22%) in comparison to the BPH control cohort, which frequently showed LOH at loci 8q21, 8p21, 9p21, and 11q22 (D8S286, D8S360, D9S1748, and D11S898, each 6%). These results indicate that microsatellite analysis using plasma DNA may be an interesting tool for molecular screening of PCa patients.

Structural organization and expression of human MTUS1, a candidate 8p22 tumor suppressor gene encoding a family of angiotensin II AT2 receptor-interacting proteins, ATIP

The Mitochondrial Tumor suppressor 1 (MTUS1) gene is a newly identified candidate tumor suppressor gene at chromosomal position 8p22. We report here that MTUS1 encodes a family of proteins whose leader member (ATIP1) was previously isolated in our laboratory as a novel interacting partner of the angiotensin II AT2 receptor involved in growth inhibition (Nouet, JBC 279: 28989-97, 2004). The MTUS1 gene contains 17 coding exons distributed over 112 kb of genomic DNA. Alternative exon usage generates three major transcripts (ATIP1, ATIP3 and ATIP4), each showing different tissue distribution. ATIP polypeptides are identical in their carboxy-terminal region carrying four coiled-coil domains. In their amino-terminal portion, ATIP polypeptides exhibit distinct motifs for localisation in the cytosol, nucleus or cell membrane, suggesting that MTUS1 gene products may be involved in a variety of intracellular functions in an AT2-dependent and independent manner. ATIP1 is ubiquitous and highly expressed in the brain. ATIP3 is the major transcript in tissues (prostate, bladder, breast, ovary, colon) corresponding to cancer types with frequent loss of heterozygosity at 8p22. Interestingly, ATIP4 is a brain-specific transcript highly abundant in the cerebellum and fetal brain. High evolutionary conservation of ATIP amino-acid sequences suggests important biological roles for this new family of proteins in tumor suppression and/or brain function.

Allelic imbalance and biochemical outcome after radical prostatectomy

OBJECTIVE

To compare the incidence of allelic imbalance (AI) in men with rapid disease progression with those who remained disease free after radical prostatectomy, with the aim of identifying genetic markers to predict prognosis and guide further treatment.

PATIENTS AND METHODS

Tumour and normal DNA were extracted from two matched groups of 31 men with extracapsular node-negative (pT3N0) prostate cancer who had undergone radical prostatectomy. One group comprised men who developed biochemical recurrence within 2 years of surgery and one group were prostate-specific antigen (PSA) free for at least 3 years. Men were matched for Gleason grade, preoperative PSA and pathological stage. Analysis was performed by genotyping.

RESULTS

Allelic imbalance was analysed using 30 markers, and was seen in at least one marker in 57 (92%) of the cases. Deletion at marker D10S211 (10p12.1) was significantly more common in the relapse group than the non-relapse group (35 vs 5%, P=0.03).

CONCLUSIONS

This study demonstrates significant association between AI on chromosome 10 and biochemical progression after radical prostatectomy.

Allelic loss at 16q23.2 is associated with good prognosis in high grade prostate cancer

PURPOSE

Loss of heterozygosity (LOH) at 16q23.2 is an early and frequent event in prostate cancer. LOH is thought to be involved in tumor development and progression mainly through inactivation of tumor suppressor genes. However, it has been demonstrated that LOH at 16q23.2 is an independent marker of good prognosis in breast cancer. In the present study, we evaluated the clinical relevance of 16q23.2 LOH in prostate cancer, together with other LOH frequently associated with this disease.

EXPERIMENTAL DESIGN

Tumoral and normal DNA were extracted from 61 radical prostatectomies, including 30 pT2 tumors with low Gleason score 5,6 (group 1), and 31 pT3 high grade (G8-9) tumors (group 2). Median follow-up after surgery was 42 months. Three patients reccured in group 1, and 20 in group 2. LOH analysis was performed using highly informative microsatellites markers, at 16q23.2, and at other chromosome loci frequently deleted in prostate cancer: 7q31, 8p22, 12p13, 13q14, and 18q21.

RESULTS

LOH at 16q23.2 is associated with low stage low grade tumors and lower preoperative PSA, while LOH at 8p22 is more frequent in high stage high grade prostate cancer. In group 2, 16q23.2 LOH was the only predictor of disease-free survival in univariate and multivariate analysis, and the cumulative LOH rate was not higher in patients non-deleted for 16q23.2.

CONCLUSION

These results emphasize the interest of 16q23.2 as an independent prognostic factor in high-grade prostate cancer, and suggest that this chromosomal region may contain a gene involved in tumor progression.

Clinical relevance of genetic instability in prostatic cells obtained by prostatic massage in early prostate cancer

We investigated whether genetic lesions such as loss of heterozygosity (LOH) are detected in prostatic cells obtained by prostatic massage during early diagnosis of prostate cancer (CaP) and discussed their clinical relevance. Blood and first urine voided after prostatic massage were collected in 99 patients with total prostate-specific antigen (PSA) between 4 and 10 ng ml⁻¹, prior to prostate biopsies. Presence of prostatic cells was confirmed by quantitative RT–PCR analysis of PSA mRNA. Genomic DNA was analysed for LOH on six chromosomal regions. One or more allelic deletions were found in prostatic fluid from 57 patients analysed, of whom 33 (58%) had CaP. Sensitivity and specificity of LOH detection and PSA free to total ratio <15% for positive biopsy were respectively 86.7 and 44% (P=0.002) for LOH, and 55 and 74% (P=0.006) for PSA ratio <15%. Analysis of LOH obtained from prostatic tumours revealed similar patterns compared to prostatic fluid cells in 86% of cases, confirming its accuracy. The presence of LOH of urinary prostatic cells obtained after prostatic massage is significantly associated with CaP on biopsy and may potentially help to identify a set of patients who are candidates for further prostate biopsies.

High frequency of allelic losses in high-grade prostate cancer is associated with biochemical progression after radical prostatectomy

Loss of heterozygosity (LOH) is the most consistent genetic change in prostate cancer (CaP). We aimed, to correlate specific LOH and the overall LOH frequency, to disease progression after radical prostatectomy (RP) in high-grade CaP. Between January 1990 through December 1998, 126 patients who underwent RP (cT1-T2), Gleason 8-10, were pT3, or pN1, or SM(+) (surgical margins). Nine were lost of follow-up, 39/117 (33%) had no biochemical progression (mean follow-up: 45 months). After exclusion for preoperative PSA >50 ng/mL, a case-control study was designed by matching 26 of these cases with 26 similar patients without biochemical progression (criteria: pT, pN, year of surgery). Using microsatellite markers, LOH were assessed on six chromosomal regions (7q31, 8p22, 12p13, 13q14, 16q23.2, 18q21). No prognostic value was associated with LOH at any one specific locus. However, the overall LOH frequency (five classes, cutoff of 60%), was significantly higher if progression (P = 0.02; P = 0.03) in SM(+) patients, and was near statistical significance (P = 0.08; P = 0.07) for the overall case-control population. In multivariate analysis (overall population), the overall LOH rate > or =60% was independently associated with progression [P = 0.035; Odds Ratio (OR) = 5.54]. An overall LOH rate > or =60% predicted poor outcome in 85% of SM(+) patients and 69% of the whole population. Our results suggest that the overall rate of LOH at chromosomal "hot spots" is more likely to be predictive of recurrence than the presence of LOH at any one particular locus. Moreover, the identification of a threshold of LOH could help in predicting patients with poor outcome who may be candidates for local or systemic adjuvant therapies.

A screen for genes that suppress loss of contact inhibition: identification of ING4 as a candidate tumor suppressor gene in human cancer

We have devised a screen for genes that suppress the loss of contact inhibition elicited by overexpression of the protooncogene MYCN. The initial application of this screen detected nine distinctive suppressors within a representative human cDNA library. One of these genes was ING4, a potential tumor suppressor gene that maps to human chromosome 12p13. Ectopic expression of ING4 suppressed the loss of contact inhibition elicited by either MYCN or MYC but had no direct effect on cellular proliferation. Pursuing the possibility that ING4 might be a tumor suppressor gene, we found inactivating mutations in ING4 transcripts from various human cancer cell lines. In addition, we used comparative genomic hybridization to detect deletion of the ING4 locus in 10-20% of human breast cancer cell lines and primary breast tumors. Ectopic expression of ING4 attenuated the growth of T47D human breast cancer cells in soft agar. We conclude that ING4 is a strong candidate as a tumor suppressor gene.

Selective capture of prostatic basal cells and secretory epithelial cells for proteomic and genomic analysis☆

Basal cells play an undefined role in signaling the growth and differentiation of normal secretory epithelial cells in the human prostate. Because basal cells disappear during malignant transformation, we hypothesize that loss of basal cell function may have a permissive role in progression of prostate intraepithelial neoplasia into invasive carcinoma. We describe an immuno-laser capture microdissection approach to selectively capture basal cells. Using surface-enhanced laser desorption/ionization time-of-flight mass spectrometry, we identified several protein candidates selectively expressed in microdissected basal cells. We also demonstrate that the RNA derived form this technique is an excellent source for gene-array studies. Thus, we provide evidence that proteomic and microgenomic techniques can be successfully applied to investigate the expression profiles of basal and secretory cells after immuno-capture.