TMPRSS2 is a tumor suppressor

Details TMPRSS2 is a tumor suppressor TMPRSS2 is a tumor suppressor

2000-10-18

2002-09-03

Caputa, Anthony C. (Department: 1642)

Chemistry: molecular biology and microbiology

Measuring or testing process involving enzymes or...

C435S006120, C435S007400, C435S007920, C435S007930, C435S183000, C514S001000, C514S002600, C514S008100, C514S012200, C530S350000

Reexamination Certificate

active

06444419

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention is directed to the TMPRSS2 gene and to methods for diagnosing predisposition to cancer resulting from mutations in TMPRSS2. TMPRSS2 was first identified by Paoloni-Giacobino et al. (1997). It maps to chromosome 21q22.3 and encodes a 492 amino acid long human serine protease which includes three identified domains: transmembrane, LDLRA (LDL receptor class A) and SRCR (scavenger receptor cysteine-rich domain). The transmembrane domain consists of amino acid residues 84-106. The LDLRA domain consists of amino acid residues 113-148. The SRCR domain consists of amino acid residues 149-242.
Because TMPRSS2 belongs to the SRCR superfamily (reviewed in Resnick et al., 1994) and one member of this family, DMBT1, was recently shown to be deleted in malignant brain tumors (Mollenhauer et al., 1998), we decided to examine this Qene to determine whether it is related to any cancer. The biochemical function of the SRCR domain is not well established. This domain appears to be involved with binding to other cell-surface or extracellular molecules. For example, the SRCR domain of a cell surface protein CD6 binds to ALCAM (activated leukocyte cell adhesion molecule) (Whitney et al., 1995).
The genetics of cancer is complicated, involving multiple dominant, positive regulators of the transformed state (oncogenes) as well as multiple recessive, negative regulators (tumor suppressor genes). Over one hundred oncogenes have been characterized. The number of tumor suppressor genes is expected to increase beyond fifty (Knudson, 1993).
The involvement of so many genes underscores the complexity of the growth control mechanisms that operate in cells to maintain the integrity of normal tissue. This complexity is manifested in another way. So far, no single gene has been shown to participate in the development of all, or even the majority of human cancers. The most common oncogenic mutations are in the H-ras gene, found in 10-15% of all solid tumors (Anderson et al., 1992). The most frequently mutated tumor suppressor gene is the p53 gene, mutated in roughly 50% of all tumors. Without a target that is common to all transformed cells, the dream of a “magic bullet” that can destroy or revert cancer cells while leaving normal tissue unharmed is improbable. The hope for a new generation of specifically targeted antitumor drugs may rest on the ability to identify tumor suppressor genes or oncogenes that play general roles in control of cell division.
Some of the tumor suppressor genes, which have been cloned and characterized, influence susceptibility to: 1) retinoblastoma (RB1); 2) Wilms' tumor (WT1); 3) Li-Fraumeni (TP53); 4) Familial adenomatous polyposis (APC); 5) Neurofibromatosis type 1 (NF1); 6) Neurofibromatosis type 2 (NF2); 7) von Hippel-Lindau syndrome (VHL); and 8) Multiple endocrine neoplasia type 2A (MEN2A).
Tumor suppressor loci that have been mapped genetically but not yet isolated include genes for: Multiple endocrine neoplasia type 1 (MEN1); Lynch cancer family syndrome 2 (LCFS2); Neuroblastoma (NB); Basal cell nevus syndrome (BCNS); Beckwith-Wiedemann syndrome (BWS); Renal cell carcinoma (RCC); Tuberous sclerosis 1 (TSC1); and Tuberous sclerosis 2 (TSC2). The tumor suppressor genes that have been characterized to date encode products with similarities to a variety of protein types, including DNA binding proteins (WT1), ancillary transcription regulators (RB 1), GTPase activating proteins or GAPs (NF 1), cytoskeletal components (NF2), membrane bound receptor kinases (MEN2A), and others with no obvious similarity to known proteins (APC and VHL).
In many cases, the tumor suppressor gene originally identified through genetic studies has been shown in some sporadic tumors to be lost or mutated. This result suggests that regions of chromosomal aberration may signify the position of important tumor suppressor genes involved both in genetic predisposition to cancer and in sporadic cancer.
One of the hallmarks of several tumor suppressor genes characterized to date is that they are deleted at high frequency in certain tumor types. The deletions often involve loss of a single allele, a so-called loss of heterozygosity (LOH), but may also involve homozygous deletion of both alleles. For LOH, the remaining allele is presumed to be nonfunctional, either because of a preexisting inherited mutation, or because of a secondary sporadic mutation. Whereas LOH events commonly involve chromosomal deletions spanning many megabases of DNA, homozygous deletions are relatively small in size, probably due to the presence of essential genes in their proximity. Indeed, the identification of tumor suppressor genes has been facilitated by the discovery of homozygous deletions present within the genomes of cancer cell lines and xenografts; examples include p16 (Kamb et al., 1994), DPC4 (Hahn et al., 1996), BRCA2 (Wooster et al., 1995; Tavtigian et al., 1996) and MMAC1/PTEN (Steck et al., 1997; Li et al., 1997).
Melanoma is a common cancer afflicting one in every hundred Americans (American Cancer Society, 1992). Environmental influences, such as exposure to ultraviolet light, play a large role in melanoma incidence, but heredity is also a contributing factor. A gene for familial melanoma, MLM, has been mapped to chromosome 9p21 (Cannon-Albright et al., 1992; Nancarrow et al., 1993; Gruis et al., 1993; Goldstein et al., 1994). Possession of a single predisposing allele at the MLM locus increases the probability that an individual will develop melanoma by up to approximately 50-fold. MLM belongs to the growing family of suspected tumor suppressor genes. Predisposition to melanoma is inherited as a dominant Mendelian trait, yet predisposing mutations in MLM are thought to act as somatic recessive alleles in the manner originally proposed by Knudson (1971). In a predisposed individual who carries one wild-type and one mutant MLM allele, dividing cells undergo secondary mutational events that involve loss or inactivation of the wild-type copy of MLM, thereby uncovering the inherited mutant MLM allele. Conversely, a single wild-type copy of the gene prevents the onset of malignancy.
Chromosomal aberrations in the vicinity of MLM at 9p21 have been extensively characterized in several different tumor types, including glioma cell lines, non-small cell lung lines and acute lymphoblastic leukemia lines (Olopade et al., 1992; Olopade et al., 1993; Lukeis et al., 1990; Diaz et al., 1988; Middleton et al., 1991; Fountain et al., 1992; Cheng et al., 1993; James et al., 1993). Thus, based on the frequency of 9p21 chromosomal abnormalities in non-melanoma tumor cells, it is probable the MLM region contains a gene (or genes) that participates at least in the progression of several different tumor types. These events involve LOH as well as a high frequency of homozygous deletion.
Cells in tissues have only three serious options in life—they can grow and divide, not grow but stay alive, or die by apoptosis. Tumors may arise either by inappropriate growth and division or by cells failing to die when they should. One of the mechanisms for controlling tumor growth might involve direct regulation of the cell cycle. For example, genes that control the decision to initiate DNA replication are attractive candidates for oncogenes or tumor suppressor genes, depending on whether they have a stimulatory or inhibitory role in the process. Progression of eukaryotic cells through the cell cycle (G
1
, S, G
2
and M phases) is governed by the sequential formation, activation and subsequent inactivation of a series of cyclin/cyclin-dependent kinase (Cdk) complexes. Cyclin D's/Cdk2,4,5, Cyclin E/Cdk2, Cyclin A/Cdk2 and Cyclin B/A/Cdk2 have been shown to be involved in this process. Cyclin D's and Cdk2, Cdk4 and Cdk5 have been implicated in the transition from G
1
to S; that is, when cells grow and decide whether to begin DNA replication. Additional cell cycle control elements have recently been discovered. These elements are inhibitors of Cdks (Cdk inhibitors, CkI), and include Far1, p21, p4

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