Down-regulation of microRNA 106b is involved in p21-mediated cell cycle arrest in response to radiation in prostate cancer cells

BACKGROUND

microRNAs (miRNAs) are endogenous short non-coding RNAs, and play a pivotal role in regulating of a variety of cellular processes, including proliferation and apoptosis, both of which are cellular responses to radiation treatment. The purpose of this study is to identify candidate miRNAs whose levels are altered in response to radiation in prostate cancer cells and to investigate the molecular pathway of such miRNAs in the regulation of radiation-induced cellular response.

METHODS

Using a miRNA microarray assay, we screened 132 cancerous miRNAs in LNCaP cells in response to radiation treatment. The function of one candidate miRNA was investigated for checkpoint protein expression, cell cycle arrest, cell proliferation, and cell survival in cells transfected with precursor or antisense miRNA.

RESULTS

In response to radiation, multiple miRNAs, including mi-106b, showed altered expression. Cells transfected with precursor miR-106b were able to suppress radiation-induced p21 activation. Functionally, exogenous addition of precursor miR-106b overrode the G2/M arrest in response to radiation and resulted in a transient diminishment of radiation-induced growth inhibition.

CONCLUSION

We have shown a novel role of miR-106b, in the setting of radiation treatment, in regulating the p21-activated cell cycle arrest. Our finding that miR-106b is able to override radiation-induced cell cycle arrest and cell growth inhibition points to a potential therapeutic target in certain prostate cancer cells whose radiation resistance is likely due to consistently elevated level of miR-106b.

Multi-institutional trial of accelerated hypofractionated intensity-modulated radiation therapy for early-stage oropharyngeal cancer (RTOG 00-22)

PURPOSE

To assess the results of a multi-institutional study of intensity-modulated radiation therapy (IMRT) for early oropharyngeal cancer.

PATIENTS AND METHODS

Patients with oropharyngeal carcinoma Stage T1-2, N0-1, M0 requiring treatment of the bilateral neck were eligible. Chemotherapy was not permitted. Prescribed planning target volumes (PTVs) doses to primary tumor and involved nodes was 66 Gy at 2.2 Gy/fraction over 6 weeks. Subclinical PTVs received simultaneously 54-60 Gy at 1.8-2.0 Gy/fraction. Participating institutions were preapproved for IMRT, and quality assurance review was performed by the Image-Guided Therapy Center.

RESULTS

69 patients were accrued from 14 institutions. At median follow-up for surviving patients (2.8 years), the 2-year estimated local-regional failure (LRF) rate was 9%. 2/4 patients (50%) with major underdose deviations had LRF compared with 3/49 (6%) without such deviations (p = 0.04). All cases of LRF, metastasis, or second primary cancer occurred among patients who were current/former smokers, and none among patients who never smoked. Maximal late toxicities Grade >or=2 were skin 12%, mucosa 24%, salivary 67%, esophagus 19%, osteoradionecrosis 6%. Longer follow-up revealed reduced late toxicity in all categories. Xerostomia Grade >or=2 was observed in 55% of patients at 6 months but reduced to 25% and 16% at 12 and 24 months, respectively. In contrast, salivary output did not recover over time.

CONCLUSIONS

Moderately accelerated hypofractionatd IMRT without chemotherapy for early oropharyngeal cancer is feasible, achieving high tumor control rates and reduced salivary toxicity compared with similar patients in previous Radiation Therapy Oncology Group studies. Major target underdose deviations were associated with higher LRF rate.

Cyclin D1 guanine/adenine 870 polymorphism with altered protein expression is associated with genomic instability and aggressive clinical biology of esophageal adenocarcinoma

PURPOSE

Altered cyclin D1 (CD1), a cell cycle regulator, may play an important role in imparting aggressive nature to esophageal adenocarcinoma (EAC). CD1 gene single nucleotide polymorphism G/A870 results in two alternatively spliced transcripts, CD1a and CD1b. CD1b, preferentially encoded by the A870 allele, is putatively oncogenic. We hypothesized that CD1 A870 allele would be associated with higher CD1 protein expression, and increased genomic instability during EAC evolution, leading to more aggressive phenotype.

PATIENTS AND METHODS

One hundred twenty-four archival specimens of EAC, and 39 associated Barrett's esophagus (BE) specimens were examined for CD1 genotype, CD1 protein expression, and chromosome 9 polysomy (representing genomic instability). We correlated CD1 genotypes with CD1 protein expression, genomic instability, age at diagnosis of EAC, and overall survival (OS).

RESULTS

The A870 allele was associated with higher levels of CD1 protein expression in EAC (P = .032); in BE (P = .01) where it was associated with concomitant increased chromosome 9 polysomy (P = .002); and with a younger age at diagnosis (P < .001) and poor OS (P = .0003) of EAC patients.

CONCLUSION

Our data suggest that CD1 A870 background may be imparting aggressive phenotype to EAC. It provides a molecular basis to explain the clinical biology associated with CD1 polymorphism whereas aberrant nuclear accumulation of CD1 protein enhances the acquisition of genomic instability (ie, clonal diversity), thus leading to early age of EAC diagnosis and poor OS. CD1 genotyping with other biomarkers may help create a biomarker-based prognostic model for EAC and CD1 may also serve as a therapeutic target.

Pretherapy nuclear factor-κB status, chemoradiation resistance, and metastatic progression in esophageal carcinoma

BACKGROUND

Transcriptional factor nuclear factor-kappaB (NF-kappaB) seems to be associated with aggressive clinical biology (chemoradiation resistance and metastatic progression) of esophageal cancer. We hypothesized that activated NF-kappaB would define clinical biology irrespective of the type of chemotherapy or sequence administered.

METHODS

Pretherapy and/or posttherapy cancer specimens were examined for activated NF-kappaB and correlated with pathologic response to chemoradiation, metastatic potential, overall survival, disease-free survival, and type of chemotherapy or sequence used.

FINDINGS

Eighty patients undergoing chemotherapy and concurrent radiation were studied. Activated NF-kappaB prior to any therapy was associated with the lack of complete pathologic response (pathCR, P = 0.006). Forty-five (78%) of 58 patients achieving <pathCR had activated NF-kappaB in pretherapy and/or posttherapy cancer specimens versus 2 (9%) of 22 patients with pathCR (P = 0.001). Twenty-four (51%) of 47 patients with activated NF-kappaB in cancer developed metastases versus 7 (21%) of 22 patients with negative NF-kappaB in cancer (P = 0.01). At a median follow-up of 32 months, 25 (53%) of 47 patients with activated NF-kappaB cancer had died versus 3 (9%) of 33 patients with negative NF-kappaB cancer. NF-kappaB activation was the only independent predictor of disease-free survival (P = 0.01) and overall survival (P = 0.007) in a multivariate model. The class of chemotherapy or its sequence had no effect on NF-kappaB expression or patient outcome.

CONCLUSIONS

Our data are the first to show that pretreatment-activated NF-kappaB significantly correlates with clinical biology of esophageal cancer, and most importantly, with pathCR. To therapeutically exploit NF-kappaB-regulated genes and their pathways, further research is warranted.

Functional imaging in treatment planning in radiation therapy: a review

The remarkable technical developments obtained in radiation oncology have resulted in an increasing use of image-based treatment planning in radiation therapy for three-dimensional and intensity modulated radiation therapy, stereotactic irradiation and image-guided brachytherapy. There has been increased use of computer-based record and verify systems as well as electronic portal imaging to enhance treatment delivery. From the data presented it is evident that PET scanning and other functional imaging techniques play a major role in the definition of tumor extent and staging of patients with cancer. The recent introduction of a combined CT and PET scanner will substantially simplify image acquisition and treatment planning.