K-RAS mutation in transitional cell carcinoma of urinary bladder

Simultaneous activation of Kras and inactivation of p53 induces soft tissue sarcoma and bladder urothelial hyperplasia

The development of the Cre recombinase-controlled (Cre/LoxP) technique allows the manipulation of specific tumorigenic genes, temporarily and spatially. Our original intention of this study was to investigate the role of Kras and p53 in the development of urinary bladder cancer. First, to validate the effect of intravesical delivery on Cre recombination (Adeno-Cre), we examined activity and expression of β-galactosidase in the bladder of control ROSA transgenic mice. The results confirmed specific recombination as evidenced by β-galactosidase activity in the bladder urothelium of these mice. Then, we administered the same adenovirus into the bladder of double transgenic Kras^LSLG12D/+. p53^fl/fl mice. The virus solution was held in place by a distal urethral retention suture for 2 hours. To our surprise, there was a rapid development of a spindle-cell tumor with sarcoma characteristics near the suture site, within the pelvic area but outside the urinary track. Since we did not see any detectable β-galactosidase in the area outside of the bladder in the validating (control) experiment, we interpreted that this sarcoma formation was likely due to transduction by Adeno-Cre in the soft tissue of the suture site. To avoid the loss of skin integrity associated with the retention suture, we transitioned to an alternative technique without suture to retain the Adeno-Cre into the bladder cavity. Interestingly, although multiple Adeno-Cre treatments were applied, only urothelial hyperplasia but not carcinogenesis was observed in the subsequent experiments of up to 6 months. In conclusion, we observed that the simultaneous inactivation of p53 and activation of Kras induces quick formation of spindle-cell sarcoma in the soft tissues adjacent to the bladder but slow formation of urothelial hyperplasia inside the bladder. These results strongly suggest that the effect of oncogene regulation to produce either hyperplasia or carcinogenesis greatly depends on the tissue type.

Biomarkers in bladder cancer: translational and clinical implications

Bladder cancer is associated with high recurrence and mortality rates. These tumors show vast heterogeneity reflected by diverse morphologic manifestations and various molecular alterations associated with these disease phenotypes. Biomarkers that prospectively evaluate disease aggressiveness, progression risk, probability of recurrence and overall prognosis would improve patient care. Integration of molecular markers with conventional pathologic staging of bladder cancers may refine clinical decision making for the selection of adjuvant and salvage therapy. In the past decade, numerous bladder cancer biomarkers have been identified, including various tumor suppressor genes, oncogenes, growth factors, growth factor receptors, hormone receptors, proliferation and apoptosis markers, cell adhesion molecules, stromal factors, and oncoproteins. Recognition of two distinct pathways for urothelial carcinogenesis represents a major advance in the understanding and management of this disease. Nomograms for combining results from multiple biomarkers have been proposed to increase the accuracy of clinical predictions. The scope of this review is to summarize the major biomarker findings that may have translational and clinical implications.

Knockdown of phospholipase C-epsilon by short-hairpin RNA-mediated gene silencing induces apoptosis in human bladder cancer cell lines

Transitional cell carcinoma of bladder (TCCB) is a common malignancy worldwide, and outcomes for patients with advanced bladder cancer remain poor. To study the pathogenesis of TCCB, we investigated roles of Phospholipase C (PLC)ɛ, an effector of Ras and Rap small GTPases. RNA interference was used to knockdown PLCɛ expression in human bladder cancer cell lines (BIU-87 and T24). The expression levels of PLCɛ mRNA and protein were detected by reverse transcriptase-polymerase chain reaction and Western blot, respectively. Flow cytometry (FCM) was used to detect distribution of cell cycle. Cellular apoptosis was reflected by transmission electron microscopy and the expression of bcl-2 and bax. We found that PLCɛ could be efficiently knocked down by shRNA. FCM assay showed that the pGenesil-PLCɛ-transfected cells were arrested at the G0/G1 phase. Silence of PLCɛ might induce apoptosis via modulation of bcl-2 and bax. In conclusion, our results suggest that PLCɛ plays an important role in the pathogenesis of human bladder cancer cells. PLCɛ may be used as a potential target of gene therapy for bladder cancer in future.

Involvement of the PLCε/PKCα pathway in human BIU-87 bladder cancer cell proliferation

PLCε (phospholipase Cε), one of effectors belonging to the small GTPase superfamily, has been suggested to play a crucial role in carcinogenesis. However, its bio-function in bladder cancer has never been demonstrated. In our previous study, we found that PLCε mRNA was highly expressed in bladder cancer tissues. In the present study, we silenced the PLCε gene by shRNA (small-hairpin RNA) in the bladder cancer cell line BIU-87. The results showed that it significantly inhibited cell proliferation and arrested the cell cycle at G0/G1-phase. The regulation of cell characteristics has been related to PKCα (protein kinase Cα) activity. Further study showed that knockdown of the PLCε gene down-regulated oncogenes c-fos and c-jun. These results indicate that PLCε plays a crucial role in bladder cancer, and PLCε may be a key molecule regulating the signal pathway of bladder cancer proliferation.

K-Ras and β-catenin mutations cooperate with Fgfr3 mutations in mice to promote tumorigenesis in the skin and lung, but not in the bladder

The human fibroblast growth factor receptor 3 (FGFR3) gene is frequently mutated in superficial urothelial cell carcinoma (UCC). To test the functional significance of FGFR3 activating mutations as a 'driver' of UCC, we targeted the expression of mutated Fgfr3 to the murine urothelium using Cre-loxP recombination driven by the uroplakin II promoter. The introduction of the Fgfr3 mutations resulted in no obvious effect on tumorigenesis up to 18 months of age. Furthermore, even when the Fgfr3 mutations were introduced together with K-Ras or β-catenin (Ctnnb1) activating mutations, no urothelial dysplasia or UCC was observed. Interestingly, however, owing to a sporadic ectopic Cre recombinase expression in the skin and lung of these mice, Fgfr3 mutation caused papilloma and promoted lung tumorigenesis in cooperation with K-Ras and β-catenin activation, respectively. These results indicate that activation of FGFR3 can cooperate with other mutations to drive tumorigenesis in a context-dependent manner, and support the hypothesis that activation of FGFR3 signaling contributes to human cancer.

Ras mutation cooperates with β-catenin activation to drive bladder tumourigenesis

Mutations in the Ras family of proteins (predominantly in H-Ras) occur in approximately 40% of urothelial cell carcinoma (UCC). However, relatively little is known about subsequent mutations/pathway alterations that allow tumour progression. Indeed, expressing mutant H-Ras within the mouse bladder does not lead to tumour formation, unless this is expressed at high levels. The Wnt signalling pathway is deregulated in approximately 25% of UCC, so we examined if this correlated with the activation of MAPK signalling in human UCC and found a significant correlation. To test the functional significance of this association we examined the impact of combining Ras mutation (H-Ras(Q61L) or K-Ras(G12D)) with an activating β-catenin mutation within the mouse bladder using Cre-LoxP technology. Although alone, neither Ras mutation nor β-catenin activation led to UCC (within 12 months), mice carrying both mutations rapidly developed UCC. Mechanistically this was associated with reduced levels of p21 with dependence on the MAPK signalling pathway. Moreover, tumours from these mice were sensitive to MEK inhibition. Importantly, in human UCC there was a negative correlation between levels of p-ERK and p21 suggesting that p21 accumulation may block tumour progression following Ras mutation. Taken together these data definitively show Ras pathway activation strongly cooperates with Wnt signalling to drive UCC in vivo.

Management of bladder cancer: current and emerging strategies

Cancer of the urinary bladder is the fifth most prevalent solid tumour in the US. Urothelial carcinoma is the most common form of bladder cancer, accounting for about 90% of cases. About 25% of patients with bladder cancer have advanced disease (muscle-invasive or metastatic disease) at presentation and are candidates for systemic chemotherapy. Urothelial carcinoma is a chemo-sensitive disease, with a high overall and complete response rate to combination chemotherapy. In the setting of muscle-invasive urothelial carcinoma, use of neoadjuvant chemotherapy is associated with overall survival benefit. The role of adjuvant chemotherapy in this setting is yet to be validated. In the setting of metastatic disease, use of cisplatin-based regimens improves survival. However, despite initial high response rates, the responses are typically not durable leading to recurrence and death in the vast majority of these patients. Currently, there is no standard second-line therapy for patients in whom first-line chemotherapy for metastatic disease has failed. Many newer chemotherapeutic agents have shown modest activity in urothelial carcinoma. Improved understanding of molecular biology and pathogenesis of urothelial carcinoma has opened avenues for the use of molecularly targeted therapies, several of which are being tested in clinical trials. Currently, several novel drugs seem particularly promising including inhibitors of the epidermal growth factor receptor pathway, such as cetuximab, and inhibitors of tumour angiogenesis, such as bevacizumab and sunitinib. Development of reliable molecular predictive markers is expected to improve treatment decisions, therapy development and outcomes in urothelial carcinoma. Funding of and participation in clinical trials are key to advancing the care of urothelial cancer patients. Current and emerging strategies in the medical management of urothelial carcinoma are reviewed.

Loss of heterozygosity of Kras2 gene on 12p12-13 in Chinese colon carcinoma patients

AIM: To study the loss of heterozygosity (LOH) on 12p12-13 in Chinese colon carcinoma patients.

METHODS: DNA was extracted from 10 specimens of cancer tissue, 10 specimens of adjacent tissue and 10 specimens of normal tissue, respectively. LOH of Kras2 gene was analyzed by polymerase chain reaction (PCR) and denaturing polyacrylamide gel electrophoresis using 11 microsatellite markers on 12p-12-13.

RESULTS: LOH of Kras gene was detected at least on one marker of 12p-12-13 in 30% (3/10) of adjacent tissue specimens. The highest frequency of LOH was identified on D12S1034 in 28.57% (2/7) of adjacent tissue specimens. LOH was detected at least on one marker of 12p12-13 in 60% (6/10) of carcinoma tissue specimens, the most frequent LOH was found on D12S1034 and D12S1591 in 42.86% (3/7) of carcinoma tissue specimens. LOH was detected in 30% (3/10) of carcinoma tissue specimens, 30% (3/10) of adjacent tissue specimens, and no signal in 1% (1/0) carcinoma tissue specimen. The occurrence of LOH did not correlate with sex, age, tumor size and lymph node metastasis.

CONCLUSION: Genomic instability may occur on 12p-12-13 of Kras2 gene in the development and progression of colon carcinoma. The high LOH of Kras2 gene may directly influence the transcription and translation of wild type Kras2 gene.

FGFR3 and Ras gene mutations are mutually exclusive genetic events in urothelial cell carcinoma

Fibroblast growth factor receptor 3 (FGFR3) mutations are frequent in superficial urothelial cell carcinoma (UCC). Ras gene mutations are also found in UCC. As oncogenic activation of both FGFR3 and Ras is predicted to result in stimulation of the mitogen-activated protein kinase (MAPK) pathway, we hypothesized that these might be mutually exclusive events. HRAS mutation has been widely studied in UCC, but all three Ras gene family members have not been screened for mutation in the same sample series. We screened 98 bladder tumours and 31 bladder cell lines for mutations in FGFR3, HRAS, NRAS and KRAS2. FGFR3 mutations were present in 54 tumours (55%) and three cell lines (10%), and Ras gene mutations in 13 tumours (13%) and four cell lines (13%). These included mutations in all three Ras genes; ten in HRAS, four in KRAS2 and four in NRAS and these were not associated with either tumour grade or stage. In no cases were Ras and FGFR3 mutation found together. This mutual exclusion suggests that FGFR3 and Ras gene mutation may represent alternative means to confer the same phenotype on UCC cells. If these events have biological equivalence, Ras mutant invasive UCC may represent a novel subgroup.

Molecular margin analysis predicts local recurrence after sublobar resection of lung cancer

Sublobar resection for early-stage lung cancer has been used for patients who are not candidates for lobar resection. However, sublobar resection is associated with high local recurrence rates in the context of tumor-free parenchymal margins. The mechanism underlying this high recurrence rate is not well understood. We hypothesized that this elevated risk of local recurrence is due to undetected tumor cells present at parenchymal margins thought to be negative by conventional light microscopy. Thirteen of 44 patients who underwent sublobar resection for lung cancer were found to have a k-ras mutation at codon 12.1. A novel fluorescence-based assay for detection of rare copies of mutant DNA in a background of wild-type DNA, fluorescent gap ligase chain reaction, was used to quantitate the mutant/wild-type DNA in a range of 1 to 1/10,000 in histologically normal margins from these resections. Nine of 13 patients had at least one margin with the number of mutant cells over or equal to a threshold of 1/5,000, and of these, 6/9 (67%) recurred locally. None of the remaining 4 patients without mutant DNA in any surgical margin had evidence of recurrence. The higher rate of local recurrence associated with sublobar resection of lung cancer is likely due to the occult presence of tumor cells at resection margins. These occult tumor cells can be quantitated using a novel fluorescence-based assay and define a group of patients at high risk for local recurrence who are candidates for adjuvant therapy or more extensive resection. This methodology may be adaptable to a real-time format for intraoperative use.

A phase II trial of R115777, an oral farnesyl transferase inhibitor, in patients with advanced urothelial tract transitional cell carcinoma

BACKGROUND

R115777 is a potent farnesyl transferase inhibitor and has significant antitumor effects in vitro and in vivo.

METHODS

The objective of the current study was to determine the objective response proportion in patients with metastatic transitional cell carcinoma (TCC) of the urothelial tract who received treatment with R115777 at a dose of 300 mg orally given twice daily for 21 days followed by 7 days of rest for every 4-week cycle. Thirty-four patients with TCC were enrolled in this Phase II study. Patients were allowed to have received a maximum of one prior systemic chemotherapy regimen, not including chemoradiation or neoadjuvant chemotherapy. All patients were required to have an Eastern Cooperative Oncology Group performance status of 0-2 and adequate bone marrow, hepatic, and kidney function.

RESULTS

Twice daily administration of oral R115777 was tolerated well. R115777 was absorbed rapidly after oral administration. Grade 3-4 neutropenia (according to the National Cancer Institute Common Toxicity Criteria [version 2.0]) was observed in 5 patients (15%). Grade 3-4 nonhematologic toxicity was rare, consisting of rash and diarrhea in 1 patient each. Two patients (6%) without prior chemotherapy demonstrated partial responses. Thirteen patients (38%) achieved disease stabilization according to World Health Organization criteria that lasted a median of 4 months. No complete responses were observed.

CONCLUSIONS

The objective response rate of R115777 was not sufficient to warrant future investigation in TCC as a single agent. Preliminary evidence of the activity of R115777 in 2 chemotherapy-naive patients may warrant further investigation in combination with first-line chemotherapy.