John D. Minna

jun-B inhibits and c-fos stimulates the transforming and trans-activating activities of c-jun

We have cloned the human jun-B gene and determined its sequence and transforming and trans-activating activities. jun-B is less potent that c-jun in transforming and immortalizing primary rat embryo cells in cooperation with activated ras (effects enhanced by c-fos and TPA); unlike c-jun, jun-B does not transform Rat-1A cells alone. However, cotransfection of c-jun and jun-B into primary rat embryo cells with c-Ha-ras results in a significant decrease in transformation compared with c-jun alone, an event reversed by TPA. Cotransfection of c-jun and jun-B with or without c-fos into F9 teratocarcinoma cells results in decreased trans-activation of AP-1 compared with either gene alone. Introduction of jun-B into primary rat c-jun/ras transformants or c-jun into jun-B/ras transformants also results in a decrease in trans-activation. These findings demonstrate that, whereas jun-B and c-jun each participate in AP-1 trans-activation and malignant transformation, interactions between them involve negative regulation.

Non-small cell lung cancer part: I Biology, diagnosis, and staging

Squamous, large cell, and adenocarcinoma, collectively termed non-small cell lung cancer (NSCLC), are diagnosed in approximately 75% of patients with lung cancer in the United States. The treatment of these three tumor cell types is approached in virtually identical fashion because, in contrast to small cell carcinoma of the lung, NSCLC more frequently presents with localized disease at the time of diagnosis and is thus more often amenable to surgical resection but less frequently responds to chemotherapy and irradiation. Cigarette smoking is etiologically related to the development of NSCLC in the great majority of cases. Genetic mutations in dominant oncogenes such as K-ras, loss of genetic material on chromosomes 3p, 11p, and 17p, and deletions or mutations in tumor suppressor genes such as rb and p53 have been documented in NSCLC tumors and tumor cell lines. NSCLC is diagnosed because of symptoms related to the primary tumor or regional or distant metastases, as an incidental finding on chest radiograph, or rarely because of a paraneoplastic syndrome such as hypercalcemia or hypertrophic pulmonary osteoarthropathy. Screening smokers with periodic chest radiographs and sputum cytologic examination has not been shown to reduce mortality. The diagnosis of NSCLC is usually established by fiberoptic bronchoscopy or percutaneous fine-needle aspiration, by biopsy of a regional or distant metastatic site, or at the time of thoracotomy. Pathologically, NSCLC arises in a setting of bronchial mucosal metaplasia and dysplasia that progressively increase over time. Squamous carcinoma more often presents as a central endobronchial lesion, while large cell and adenocarcinoma have a tendency to arise in the lung periphery and invade the pleura. Once the diagnosis is made, the extent of tumor dissemination is determined. Since most NSCLC patients who survive 5 years or longer have undergone surgical resection of their cancers, the focus of the staging process is to determine whether the patient is a candidate for thoracotomy with curative intent. The dominant prognostic factors in NSCLC are extent of tumor dissemination, ambulatory or performance status, and degree of weight loss. Stages I and II NSCLC, which are confined within the pleural reflection, are managed by surgical resection whenever possible, with approximate 5-year survival of 45% and 25%, respectively. Patients with stage IIIa cancers, in which the primary tumor has extended through the pleura or metastasized to ipsilateral or subcarinal lymph nodes, can occasionally be surgically resected but are often managed with definitive thoracic irradiation and have 5-year survival of approximately 15%.(ABSTRACT TRUNCATED AT 400 WORDS)

Ten-year survival of patients with small-cell lung cancer treated with combination chemotherapy with or without irradiation.

We evaluated the 10- to 15-year outcome of 252 patients with small-cell lung cancer entered into therapeutic clinical trials with or without chest and cranial irradiation. Thirty-two patients (13%) survived free of cancer for 2 or more years. Twelve patients (5%) survived at least 10 years free of cancer, and 10 patients are currently alive and free of cancer beyond 10 years. Six of these 10 patients currently function at a level comparable with that before diagnosis. The other 22 patients who were cancer-free at 2 years have died. Nine patients died from recurrent small-cell lung cancer 2 to 6.2 years after initiation of chemotherapy. Five died from non-small-cell lung cancer, three died of other malignancies, and five died of causes other than cancer. A small fraction of patients with small-cell lung cancer are cured of their original malignancy, but these patients remain at high risk for second cancers and death from other causes.

Multiple mechanisms for transcriptional regulation of the myc gene family in small-cell lung cancer

The molecular mechanisms reported to regulate the expression of myc family genes are multiple and complex and include gene amplification, transcriptional activation, transcriptional attenuation, and mRNA stability. We have investigated which of these mechanisms are responsible for the extreme variation in myc gene family mRNA levels observed in human small-cell lung cancer cell lines. In addition to gene amplification, a block to nascent mRNA chain elongation, causing attenuation of transcription, is an important regulatory mechanism controlling the steady-state levels of c-myc and L-myc mRNA. The loss of transcriptional attenuation is correlated with overexpression of these two genes in cell lines which do not show gene amplification. Expression of c-myc mRNA appears to be dependent on promoter activity and attenuator function. In contrast, regulation of expression of the N-myc gene does not involve transcriptional attenuation; steady-state mRNA levels are correlated with promoter activity as well as gene amplification. We conclude that transcriptional regulation of each member of the myc gene family is accomplished by a different assortment of complex mechanisms, including gene copy number, promoter activation, and transcriptional attenuation. Interference at multiple points in this complex regulatory process appears to be an important mechanism by which small-cell lung cancer and other human tumors evade growth control.

L-myc cooperates with ras to transform primary rat embryo fibroblasts.

Recent molecular analysis has revealed that L-myc has several domains of extremely conserved amino acid sequence homology with c-myc and N-myc, suggesting similarity of function. We tested the biologic activity of L-myc by using an expression vector containing a cDNA clone coding for the major open reading frame in the 3.9-kilobase mRNA of L-myc under the control of a strong promoter (Moloney long terminal repeat) and found that L-myc complemented an activated ras gene in transforming primary rat embryo fibroblasts. However, the efficiency of transformation was 1 to 10% of that seen with the c-myc and simian virus 40 (SV40) controls. The L-myc/ras transformants initially grew more slowly than c-myc or SV40 transformants, but once established as continuous cell lines, they were indistinguishable from cell lines derived from c-myc/ras or SV40/ras transfectants as determined by morphology, soft-agar cloning, and tumorigenicity in nude mice.

Structure and expression of the human L-myc gene reveal a complex pattern of alternative mRNA processing.

We analyzed in detail the structure of the L-myc gene isolated from human placental DNA and characterized its expression in several small-cell lung cancer cell lines. The gene is composed of three exons and two introns spanning 6.6 kilobases in human DNA. Several distinct mRNA species are produced in all small-cell lung cancer cell lines that express L-myc. These transcripts are generated from a single gene by alternative splicing of introns 1 and 2 and by use of alternative polyadenylation signals. In some mRNAs there is a long open reading frame with a predicted translated protein of 364 residues. Amino acid sequence comparison with c-myc and N-myc demonstrated multiple discrete regions with extensive homology. In contrast, other mRNA transcripts, generated by alternative processing, could encode a truncated protein with a novel carboxy-terminal end.

Diagnosis and significance of liver metastases in small cell carcinoma of the lung

One hundred fifty-seven consecutive patients with small cell lung cancer seen at the National Cancer Institute over a four-year period underwent a series of pretherapy liver staging procedures to determine optimal means of detection and prognostic implications of hepatic metastases. Liver evaluation included physical examination, liver function tests, and liver scan (radionuclide or computerized tomography [CT]), as well as percutaneous and/or peritoneoscopy-directed liver biopsy when possible (74%). Liver metastases were detected in 26% of patients. Peritoneoscopy was the most sensitive method of liver evaluation and increased the detection of liver metastases when done in a sequential fashion after percutaneous liver biopsy from 18 to a total of 27 patients. Of the noninvasive procedures, radionuclide and CT liver scan were the most accurate concurring with liver biopsy in 87% of patients but permitting correct discrimination of stage in excess of 96% of patients. The accuracy of this noninvasive procedure was enhanced by an algorithm combining the results of radionuclide liver scan with liver function tests to detect patients with high or low likelihood of liver involvement. The survival and response of patients with liver metastases was significantly worse than those without such metastases with no three-year disease-free survivors among patients with liver metastases.

Gastrin-releasing peptide (GRP, mammalian bombesin) in the pathogenesis of lung cancer

Established human lung cancer exhibits a complex pattern of genetic changes as well as several distinct autocrine growth factor loops for regulatory peptides. The best studied example is that of gastrin-releasing peptide (GRP), the mammalian homolog of the amphibian bombesin. It is produced by up to 70% of small cell lung cancers and 10-20% of non-small cell lung cancers. GRP stimulates the growth of normal bronchial epithelium as well as that of small cell lung cancer, and its blockade with the use of antibodies or synthetic antagonists inhibits the growth of these tumors. Study of its molecular biology has revealed a complex pattern of mRNA processing which has lead to the recent isolation of a novel family of peptides termed gastrin-releasing peptide gene-associated peptides (GGAPs), present in normal and malignant human tissues. Additional efforts have been directed at characterizing the GRP receptor as well as its intracellular signaling pathways which have been reported both as G protein phospholipase C coupled events as well as activation of a membrane associated tyrosine kinase. In view of its expression in normal bronchial epithelium and its mitogenic effects on this tissue, GRP appears to play a central role in the early events of pulmonary carcinogenesis.

p53 mutations in non-small-cell lung cancers occurring in individuals without a past history of active smoking.

Accumulating evidence suggests that the p53 gene is a good target for molecular epidemiological studies. We previously reported an association between the presence of p53 mutations and lifetime cigarette consumption. Although over 675 p53 mutations have been reported in lung cancers in the literature thus far, very little is known about the nature of such changes in lung cancers in the absence of a smoking background. In the present study, we therefore analysed 69 non-small-cell lung cancer specimens from individuals without any history of active smoking and identified p53 mutations in 26% of the cases. Statistical analysis of the present cohort of non-smokers also showed absence of significant relationship between p53 mutations and age, sex, histological type or disease stage. Comparison of mutational spectra between the present results in non-smokers and previously reported mutations in smokers clearly demonstrated G:C to T:A transversions to be significantly less frequent in non-smokers than in smokers (OR 5.35, 95% CI 1.77-16.12). Interestingly, G:C to C:G and G:C to A:T mutations were also observed in tumours of non-smokers at similar frequencies to G:C to T:A mutations, suggesting that these mutations can occur relatively frequently in the absence of active smoking. This study is, to our knowledge, the largest so far analysing a well-defined cohort of non-smokers in a single laboratory.

The human L-myc gene encodes multiple nuclear phosphoproteins from alternatively processed mRNAs.

The human proto-oncogene L-myc generates at least four different mRNAs by alternative RNA processing. We have identified two phosphorylated L-myc proteins with molecular masses of 60,000 and 66,000 daltons [p60L-myc(human) and p66L-myc(human)] in a small-cell carcinoma line expressing high levels of L-myc mRNA. These proteins have a short half-life and are localized to the nuclear matrix fraction, as previously reported for the c-myc and N-myc proteins. In vitro translation experiments demonstrated that both the p60 and p66 species are encoded by a 3.9-kilobase (kb) mRNA which retains intron 1, while only the p60 protein is translated from a 3.6-kb L-myc mRNA which has had intron 1 removed. While L-myc proteins [p32L-myc(human) and p37L-myc(human)] could be synthesized in vitro from 2.2-kb mRNA templates, no such proteins were detected by immunoprecipitation in vivo. These observations suggest that alternative RNA processing of the L-myc transcript could play a role in determining the steady-state levels of the p60L-myc and p66L-myc proteins.