p53 gene mutations and abnormal retinoblastoma protein in radiation-induced human sarcomas.

The potentially carcinogenic effect of therapeutic irradiation has been recognized for many years. Second malignancies, usually sarcomas, are known to arise within or at the edge of radiation fields after a period of several years after the initial radiation exposure. We analyzed tumor cells derived from seven radiation-induced tumors for abnormalities in tumor suppressor genes p53 and retinoblastoma at the DNA sequence and/or protein level. p53 mutations were detected by exon-specific polymerase chain reaction amplification and single-strand conformation polymorphism analysis of exons 5-8 followed by direct genomic sequencing of those tumors exhibiting a variant pattern. The p53 gene was abnormal in three of six sarcomas studied. Retinoblastoma gene analysis was performed by Western immunoblot; retinoblastoma protein was under-phosphorylated in three of seven tumors and absent in one other. In all, six of seven radiation-induced human tumors have abnormalities of one or both suppressor genes. Inactivation of tumor suppressor genes by ionizing radiation may contribute to radiation carcinogenesis.

p53 mutation does not correlate with radiosensitivity in 24 head and neck cancer cell lines.

The molecular basis of tumor response to therapeutic radiation is poorly understood. Recent evidence suggests the p53 tumor suppressor gene may be involved in production of the G1 arrest seen following DNA damage by X-irradiation. It has further been proposed that tumor cells lacking the p53 checkpoint function are likely to be more sensitive to cell killing by X-irradiation because these cells enter S phase despite unrepaired DNA damage. We tested the hypothesis that tumor cells with p53 mutations are more radiosensitive by correlating the in vitro surviving fraction at 2 Gy with the mutational status of 24 head and neck squamous cell cancer cell lines. p53 mutations were present in 15 of 24 (63%) of tumors; all were homozygous changes occurring within exons 5-9. The surviving fraction at 2 Gy for the group with mutations was 0.568 compared to 0.507 for tumors without mutations (P = 0.28, Mann-Whitney test). Furthermore, no association between radiosensitivity and mutational type, codon location, or predicted amino acid alteration was noted. Our data do not support the hypothesis that p53 gene alteration predisposes tumor cells to increased cell killing via radiation.

Occurrence of p53 gene deletions and human papilloma virus infection in human head and neck cancer.

Little is known regarding the molecular genetic events in head and neck carcinoma. Epidemiological evidence suggests that both alcohol and tobacco use are related to the development of these neoplasms, and viral infections have also been postulated to play a role in some tumors. Loss of p53 tumor suppressor gene function has been found in many malignancies and can occur through either gene mutation or by interaction with the E6 protein of oncogenic human papilloma viruses (HPV). Because the mucosal surfaces of the head and neck are exposed to mutagens and HPVs, we studied DNA derived from 30 stage I-IV squamous cell carcinomas of the head and neck (9 primary tumors and 21 early passage cell lines) for p53 gene mutations as well as for the presence of oncogenic HPV DNA. Exons 2 through 11 of the p53 gene were examined using single strand conformation polymorphism analysis followed by direct genomic sequencing of all variants. HPV detection was done using polymerase chain reaction amplification with HPV E6 region type specific primers as well as L1 region degenerate ("consensus") primers; HPV type was determined by restriction fragment length polymorphism analysis of the amplified fragment as well as by Southern blotting of genomic DNA. Sixteen of 30 tumors (53%) had p53 mutations and oncogenic HPV DNA was detected in 3 of 30 (10%) tumors, none of which had p53 mutations. The p53 mutational spectrum observed was characterized by equal frequencies of transversions (6 of 16), transitions (5 of 16), and deletions (5 of 16). This distribution of mutations differs from the spectrum of p53 mutation reported in esophageal (P = 0.05) and lung (P = 0.02) cancers, two other tobacco associated neoplasms. A previously undescribed clustering of 3 mutations at codon 205 was also observed. A trend toward a shorter time to tumor recurrence after treatment was noted for those patients with tumors exhibiting p53 gene mutations, and no relationship between p53 mutations and tumor stage or node status was noted. Alteration in p53 gene function appears common in head and neck cancer, and the mutational spectrum observed may reflect the role of different mutagens or mutagenic processes than those responsible for the p53 mutations in lung and esophageal neoplasms.

Failure-free survival following brachytherapy alone or external beam irradiation alone for T1-2 prostate tumors in 2222 patients: results from a single practice.

PURPOSE: To evaluate failure-free survival (FFS) for brachytherapy (BT) alone compared to external beam radiotherapy (EBRT) alone for Stage T1-2 Nx-No Mo patients over the same time period by a single community-based practice in the prostate-specific antigen (PSA) era. MATERIALS AND METHODS: The database of Arizona Oncology Services (a multiphysician radiation oncology practice in the Phoenix metropolitan area) was reviewed for patients meeting the following criteria: (1) T1 or T2 Nx-No Mo prostate cancer; (2) no prior or concurrent therapy including hormones; (3) treatment period 12/88-12/95; and (4) treatment with either EBRT alone or BT alone ((125)I or (103)Pd). This yielded 1527 EBRT and 695 BT patients; no patients meeting the above criteria were excluded from analysis. Median follow-up for EBRT patients was 41.3 months and, for BT patients, 51.3 months. Patients were not randomized to either therapy but rather received EBRT or BT based upon patient, treating, and/or referring physician preference. PSA failure was defined according to the ASTRO consensus guidelines. The median patient age was 74 years for both groups. RESULTS: Failure-free survival at 5 years for EBRT and BT are 69% and 71%, respectively (p = 0.91). For T stage, no significant difference in FFS at 5 years is observed between EBRT and BT for either T1 (78% vs. 83%, p = 0.47) or T2 (67% vs. 67%, p = 0.89) tumors. Analysis by Gleason score shows superior outcomes for Gleason 8-10 lesions treated with EBRT vs. BT (5-year FFS 52% vs. 28%, p = 0.04); outcomes for lower grade lesions (Gleason 4-6) when analyzed by Gleason score alone do not significantly differ according to treatment received. Patients with initial PSA values of 10-20 ng/dL have an improved FFS with EBRT vs. BT at 5 years (70% vs. 53%, p = 0.001); outcomes for patients with initial PSA ranges of 0-4 ng/dL, of > 4-10 ng/dL, and > 20 ng/dL did not differ significantly by treatment received. FFS was also determined for presenting Gleason score/PSA combinations; all Gleason combinations in the initial PSA range >10-20 ng/dL had superior outcomes with EBRT compared to BT, and this reached statistical significance for Gleason scores of 2-4 (72% vs. 58%, p = 0.026), Gleason 7 (67% vs. 28%, p = 0.002), and Gleason 8-10 (63% vs. 23%, p = 0.05). CONCLUSION: In our patient population, either EBRT or BT appear equally efficacious for patients with T1/T2 disease with Gleason scores 10 ng/dL (but 20 ng/dL, as would be anticipated from the significant risks of occult distant metastasis in this group. To our knowledge, this is the first report comparing the outcome of EBRT and BT treatment in patients treated concurrently by a single group, and these results, achieved in a community-based practice, compare favorably to data from academic centers regarding external beam, brachytherapy, or surgical outcomes and should be generalizable to the community at large.

Failure free survival following brachytherapy alone for prostate cancer: comparison with external beam radiotherapy.

BACKGROUND AND PURPOSE: To compare failure free survival (FFS) for brachytherapy (BT) alone and external beam radiotherapy (EBXRT) alone. MATERIALS AND METHODS: Between 12/88 and 12/95, 1527 and 695 T(1) or T(2) Nx-No Mo prostate cancer patients (from the Arizona Oncology Services database) were treated with either EBXRT or BT, respectively. The median age was 74 years. Median follow-up for EBXRT and BT patients was 41.3 and 51.3 months, respectively. RESULTS: Overall FFS at 5 years for EBXRT and BT were 69 and 71%, respectively (P=0.91). No significant difference in FFS at 5 years was observed between EBXRT and BT for either T(1) (78 vs. 83%, P=0.47) or T(2) (67 vs. 67%, P=0.89) tumours. Superior outcomes for Gleason 8-10 lesions treated with EBXRT vs. BT (5 years FFS 52 vs. 28%, P=0.04) were observed; outcomes for lower grade lesions when analysed by Gleason score alone did not significantly differ according to treatment received. Patients with initial PSA values 10-20 ng/dl had an improved FFS with EBXRT vs. BT (70 vs. 53%, P=0.001); outcomes for patients with initial PSA ranges 0-4 ng/dl, >4-10 ng/dl and >20 ng/dl did not differ significantly with treatment received. CONCLUSIONS: EBXRT and BT appear to be equally efficacious for low-risk patients having T(1)/T(2) disease with Gleason scores <6 and PSA <10 ng/dl. Patients with Gleason scores 8-10 or PSA >10 ng/dl-<20 ng/dl) appear to fare worse with BT alone compared with EBXRT. Neither EBXRT nor BT were particularly effective for patients with a presenting PSA >20 ng/dl.

Two prostate carcinoma cell lines demonstrate abnormalities in tumor suppressor genes.

Two prostate carcinoma cell lines, DU-145 and PC-3, were examined for abnormalities in the retinoblastoma (Rb) and the p53 putative tumor suppressor genes. We found an abnormal Rb gene product in DU-145 using Western blot analysis. Polymerase chain reaction amplification followed by direct DNA sequencing demonstrated a base substitution mutation that generates a stop codon in exon 21. On Northern, Southern, and Western blot analysis, the p53 gene and its product appear to be normal in DU-145. PC-3, however, failed to demonstrate expression of either the p53 transcript on Northern blot analysis or the p53 protein on Western blot analysis, while the Rb gene products appeared to be normal on both Northern and Western blot analysis. This work extends the correlation between abnormal expression of putative tumor suppressor genes and human malignancies.