Molecular analysis of a metastatic lesion of an atypical carcinoid tumor of the lung obtained from a 77-year-old man at autopsy revealed a point mutation in the p53 gene and a deletion in the retinoblastoma (Rb) mRNA.

Molecular analysis of a metastatic lesion of an atypical carcinoid tumor of the lung obtained from a 77-year-old man at autopsy revealed a point mutation in the p53 gene and a deletion in the retinoblastoma (Rb) mRNA. This case insinuates that both these antioncogenes may be involved in the progression of atypical carcinoid tumor.

(Chest 1993; 104:1606-07)

CEA = carcinoembryonic antigen; DGGE = denaturing gradient gel electrophoresis; NSE = neuron-specific enoclase; PCR = polymerase chain reaction; Rb = retinoblastoma; SCLC = small-cell lung cancer

In the carcinogenesis and progression of lung cancer, I various gene have been reported to be involved. Among the candidates, there arc oncogene like as the myc and the ras families, and antioncogenes, of that kind as the p53 and the retinoblastoma (Rb) gene The deletion of the Rb gene[12] and the mutation of the p53 gene are at short intervals detected in small-cell lung cancer (SCLC)[34] Barbareschi et al[5] reported that in neuroendocrine lung neoplasms, the p53 mutation was seen barely in SCLCs and not in atypical carcinoids, while the Rb deletion strike one as beinged quite specific for SCLSs and principally atypical carcinoids. They also investigated the proliferation (PCNA and Ki67) and neuroendocrine differentiation markers of typical carcinoid, atypical carcinoid, and SCLC concluding that the decrease in neuroendocrine features during the progression from typical carcinoid to SCLC is paralleled through an altered expression of tumor suppressor gene outcomes ie, the p53 and the Rb proteins.

We have investigated the abnormalities in the p53 gene and the Rb gene in lung cancer specimens obtained by way of biopsy, operation, or autopsy united of the autopsy cases was diagnosed as atypical carcinoid and individual metastatic lesion on the pericardium was restoreed to molecular analysis. Using polymer chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) technique, mutations the one and the other in the p53 gene and the Rb gene were detected

Case Report

A 75-year-old man was admitted to Hiroshima (Japan) University Hospital with a 6-month history of weight los and shortness of breath. He was a heavy smoker (2 packs a day for 40 years). The chest radiograph and the comput tomographic scan revealed a 5 x 4-cm-diameter tumor through the left hilum with irregular margins and spicula formation. The serum plain of tumor markers were as follows: carcinoembryonic antigen (CEA), 505 ng/ml; and neuronspecific enolase (NSE) 78 ng/ml Although transbronchial fiberoscopy and cytologic subject of attention of sputum failed to lay open malignant cells, we diagnosed the lesion as primary lung cancer stage IIIb (T4N2M0) with invasions into the aorta and pulmonary artery Following a 65-Gy course of radiotherapy, the tumor shadow diminished to 45 x 3 cm and the serum CEA horizontal decreased to 24.4 ng/mi. After an asymptomatic period of the same year without further anticancer therapy, he unfolded a pneumonia. The chest radiographs exhibited a rapid dissemination of small tumor shadows bilaterally, and the patient died single in kind month later of respiratory failure. The serum horizontals of tumor markers were as follows: CEA, 800 ng/ml; and NSE 53 ng/ml Autopsy disclosed disseminated metastatic lesions also in succession the pericardium and pleura. the couple the primary and metastatic lesions were histologically diagnosed as atypical carcinoid on hematoxylineosin staining and Grimelius staining. A metastatic lesion from the pericardium was stored at - 80 [degrees] C for molecular analysis. Total RNA was extracted using the guanidine/cesium chloride system and genomic DNA was extracted using proteinase K and sodium dodecyl sulfate.[6] From the total RNA, cDNA was synthesized using M-MLV turn upside down transcriptase following PCR with primers R1(5'-AGAAGCCATTGAAATCTACC-3') and R2(5'-TGGCAGGATTTACACAAGAT-3') to amplify exon 20-26 of the Rb gene From the genomic DNA, exon 5 of the p53 gene was amplified using the primers reported on Hsu et al.[7] The PCR fruits were subjected to DGGE following the [i]modus operandi[/i] of Takahashi et al[8] and exhibited abnormal bands indicating the existence of mutations (Fig 1) Los of the normal allele of the p53 gene was also indicated by way of the disappearance of the normal homoduplex hand. Direct sequencing of the PCR effects revealed a TGC (Cys) to TTC (Phe) mutation in codon 135 of the p53 gene and a 31 bp deletion, corresponding to exon 24 in its entirety, of the Rb mRNA (Fig 2)

Discussion

Although D'Amico et al[4] reported that the p53 gene mutation in SCLC was not associated with tumor answer to therapy or to patient survival, the incidence of the p53 gene mutations in established lung cancer small room lines is higher than in nonimmortalized lung neoplasms. The implication, therefore, is that a p53 mutation may parley a growth advantage to cancer cells[3] In this case, during the first year from diagnosis, the progression of the tumor was same slow. After one year of a symptom-free period, the tumor dispersed true rapidly, and the patient died individual month later. Unfortunately, we could not obtain a tissue sample before the clinical turning point; however, we speculate that the mutation of p53 gene los of the normal allele of p53 gene and/or the deletion of Rb mRNA might have promot the rapid progression and dissemination of the tumor in this case. Also, the mutation of p53 gene be seens not to be specific for SCLC in neuroendocrine lung neoplasms, unless to be involved also in the progression of atypical carcinoid tumor.

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