Antisense oligonucleotides in the treatment of bladder cancer

Recent improvements in the detection and treatment of nonmuscle-invasive bladder cancer

In total, 70-80% of newly diagnosed bladder cancers are confined to the mucosa and staged as Ta, T1 or carcinoma in situ according to the 2002 tumor, lymph nodes and metastasis classification. The standard treatment for these nonmuscle-invasive bladder cancers is transurethral tumor resection with or without adjuvant intravesical chemotherapy or intravesical immunotherapy and subsequent follow-up. Diagnosis and follow-up of nonmuscle-invasive bladder cancer offers two main problems. First, approximately 10-20% of all tumors are not seen in standard cystoscopy. Additionally, frequently repeated follow-up cystoscopies are bothersome for the patient. As an adjunct to standard cystoscopy, fluorescence-guided cystoscopy has demonstrated significantly higher tumor detection rates and optimized patient treatment in recent Phase III studies. Second, routinely performed urine cytology is characterized by high specificity but low sensitivity. Today, several urine tests are available that may increase diagnostic accuracy and potentially prolong intervals of follow-up cystocopy. Owing to rather high recurrence rates after transurethral tumor resection in most tumors and high progression rates in poorly differentiated tumors, adjuvant intravesical chemotherapy or intravesical immunotherapy has gained widespread use in patients with nonmuscle-invasive bladder cancer. Only a few further immunomodulatory drugs, such as recombinant cytokines, have shown significant clinical effectiveness. Additional approaches, such as photodynamic therapy with different photosensitizers and thermotherapy in combination with intravesical chemotherapy, have been evaluated in Phase III studies.

Novel therapeutics in metastatic bladder cancer

BACKGROUND

Albeit transitional cell carcinoma of the urinary bladder is a chemosensitive neoplasm, metastatic disease is related with poor prognosis and short-term survival data.

OBJECTIVE

Cisplatin-based combination chemotherapy is recognised as the golden standard therapy for patients with inoperable locally advanced or metastatic bladder cancer. However, owing to treatment-related toxicities and short-response durations, novel treatment options or agents, with both enhanced efficacy and tolerability, have been sought.

METHODS

Reviewing the current status and addressing the future of novel anticancer therapeutics in metastatic urinary bladder cancer.

RESULTS/CONCLUSION

Non-platinum, single agents, such as gemcitabine and taxanes, as well as multidrug regimens in doublet or triplet chemotherapeutic combinations are regarded as promising alternatives. Dose intensification of conventional regimens, dose-dense sequential administration of new agents, the use of molecular markers for predicting chemosensitivity and the integration of biologically targeted agents to enhance chemotherapeutic efficacy are promising approaches.

In vivo evaluation of intravesical paclitaxel and combined bcl-xL antisense oligodeoxynucleotide treatment for orthotopic urothelial carcinoma

PURPOSE

To evaluate intravesical paclitaxel monotherapy and combined treatment with antiapoptotic bcl-xL antisense oligodeoxynucleotides (AS-ODNs) on urothelial carcinoma (UC).

METHODS

Forty-eight FoxN(rnu) athymic nude rats with orthotopic human bladder UC were randomized to four treatment groups [1, paclitaxel; 2, paclitaxel/bcl-xL AS-ODNs; 3, bcl-xL AS-ODNs (control); 4, medium (control)]. Three consecutive instillations were applied and weekly endoscopic tumor size measurements were performed.

RESULTS

Significant tumor size reduction was achieved in groups 1 and 2 (each P < 0.0001), whereas continuous UC growth was observed in control animals (groups 3 and 4; P < 0.0001 and P < 0.0020). Complete tumor eradication was achieved in four treated animals (groups 1 and 2). No significant difference in chemoresection effects was found between groups 1 and 2 (P = 0.2251).

CONCLUSIONS

We present an in vivo evaluation of intravesical treatment with paclitaxel and combined bcl-xL AS-ODNs. Despite efficient tumor size reduction, no gain was observed when adding bcl-xL AS-ODNs in this experimental setting.

Synthetic nucleic acids as potential therapeutic tools for treatment of bladder carcinoma

OBJECTIVES

Abnormal gene activation in human tumours including bladder cancers (bCAs) may cause altered proliferation, maturation, and apoptosis as well as development of resistance to therapeutic interventions. Therefore, silencing of abnormally activated genes appears to be a rational approach for specific target-directed and sensitising therapies.

METHODS

Of the available strategies for gene silencing, antisense-based techniques have attracted much attention and are the focus of this review. Putative target genes should be involved in essential tumour-promoting pathways, such as growth signalling, immortalisation, cell cycle regulation, apoptosis, angiogenesis, and development of therapy resistances. This review gives an overview of selected studies performed on bCA-derived cell lines and xenografts reporting down-regulation of potential target genes by antisense-based synthetic nucleic acids such as antisense oligodeoxynucleotides (AS-ODNs) and small interfering RNAs (siRNAs). Effects on proliferation of bCA cells and enhancement of the cytotoxic action of different chemotherapeutics were evaluated.

RESULTS

Knock-down of the selected target genes frequently caused an impairment of growth of different bCA cell lines originating from cell cycle arrest or increased apoptosis. In numerous studies, the pretreatment with AS-ODNs or siRNAs provoked strong enhancement of subsequent chemotherapies, emphasising the effectiveness of these inhibition approaches.

CONCLUSIONS

The application of antisense-based inhibitors in combination with chemotherapeutics might represent an alternative strategy for the adjuvant treatment of superficial bCA. Nevertheless, translation of this technology to the clinic might be hampered by inestimable off-target effects caused by AS-ODNs and their behaviour after intravesical instillation has to be evaluated in preclinical and clinical trials.

Antisense oligonucleotide therapy in the management of bladder cancer

PURPOSE OF REVIEW

In this paper, we will review the recent advances in antisense oligonucleotide therapy in the treatment of superficial bladder cancer. Bladder cancer has an exciting potential as a model to study antisense oligonucleotide therapy because of the ease of accessibility of treatment, ease of diagnosis through biopsy and urine cytology, and direct observation of treatment efficacy through cystoscopy and posttreatment biopsy.

RECENT FINDINGS

We will elaborate on the recent developments in the delivery of antisense oligonucleotide and the implications of these results on the use of antisense oligonucleotide intravesically. We will also discuss recent preclinical in-vitro results of antisense oligonucleotide therapy in different bladder cancer cell lines.

SUMMARY

Recent developments of the in-vitro and animal in-vivo effectiveness of antisense treatment in bladder cancer provide the foundation to pursue future phase I clinical trials. Antisense oligonucleotide technology is a promising tool that may become an effective method of treating bladder cancer.