Chemistry: molecular biology and microbiology – Animal cell – per se ; composition thereof; process of... – Method of regulating cell metabolism or physiology
C435S325000, C435S006120, C536S024500, C536S024310, C514S04400A
FIELD OF THE INVENTION
This invention relates to cell biology, physiology and medicine, and concerns an 88 kDa glycoprotein growth factor (“GP88 ”) and compositions and methods which affect the expression and biological activity of GP88. These compositions and methods are useful for diagnosis and treatment of diseases including cancer.
Several publications are referenced herein by Arabic numerals within parenthesis. Full citations for these references may be found at the end of the specification immediately preceding the claims.
BACKGROUND OF THE INVENTION
The proliferation and differentiation of cells in multicellular organisms is subject to a highly regulated process (1). A distinguishing feature of cancer cells is the absence of control over this process; proliferation and differentiation become deregulated resulting in uncontrolled growth. Significant research efforts have been directed toward better understanding this difference between normal and tumor cells. One area of research focus is growth factors and, more specifically, autocrine growth stimulation.
Growth factors are polypeptides which carry messages to cells concerning growth, differentiation, migration and gene expression (2). Typically, growth factors are produced in one cell and act on another cell to stimulate proliferation. However, certain malignant cells, in culture, demonstrate a greater or absolute reliance on an autocrine growth mechanism (3). Malignant cells which observe this autocrine behavior circumvent the regulation of growth factor production by other cells and are therefore unregulated in their growth.
Study of autocrine growth control advances understanding of cell growth mechanisms and leads to important advances in the diagnosis and treatment of cancer. Toward this end, a number of growth factors have been studied, including insulin-like growth factors (“IGF1 ” and “IGF2 ”), gastrin-releasing peptide (“GRP”), transforming growth factors alpha and beta (“TGF-a” and “TGF-b”), and epidermal growth factor (“EGF”).
The present invention is directed to a recently discovered growth factor. This growth factor was first discovered in the culture medium of highly tumorigenic “PC cells,” an insulin-independent variant isolated from the teratoma derived adipogenic cell line 1246. This growth factor is referred to herein as “GP88.” GP88 has been purified and structurally characterized (4). Amino acid sequencing of GP88 indicates that GP88 has amino acid sequence similarities with the mouse granulin/epithelin precursor.
Granulins/epithelins (“grn/epi”) are 6 kDa polypeptides and belong to a novel family of double cysteine rich polypeptides (5, 6). U.S. Pat. No. 5,416,192 (Shoyab et al.) is directed to 6 kDa epithelins, particularly epithelin 1 and epithelin 2. According to Shoyab, both epithelins are encoded by a common 63.5 kDa precursor, which is processed into smaller forms as soon as it is synthesized, so that the only natural products found in biological samples are the 6 kDa forms. Shoyab et al. teaches that the epithelin precursor is biologically inactive.
Contrary to the teachings of Shoyab et al., the inventor's laboratory has demonstrated that the precursor is not always processed as soon as it is synthesized. Studies, conducted in part by this inventor, have demonstrated that the precursor (i.e., GP88) is in fact secreted as an 88 kDa glycoprotein with an N-linked carbohydrate moiety of 2 kDa (4). Analysis of the N-terminal sequence of GP88 indicates that GP88 starts at amino acid 17 of the grn/epi precursor, demonstrating that the first 17 amino acids from the protein sequence deduced from the precursor cDNA correspond to a signal peptide compatible with targeting for membrane localization or for secretion (4).
Also in contrast to the teachings of Shoyab et al., GP88 is biologically active and has growth promoting activity, particularly as an autocrine growth factor for the producer cells.
SUMMARY OF INVENTION
The inventor has now unexpectedly discovered that a glycoprotein (GP88), which is expressed in a tightly regulated fashion in normal cells, is overexpressed and unregulated in highly tumorigenic cells derived from the normal cells, that GP88 acts as a stringently required growth stimulator for the tumorigenic cells and that inhibition of GP88 expression or action in the tumorigenic cells results in an inhibition of the tumorigenic properties of the overproducing cells.
It is an object of this invention to provide GP88 antagonizing compositions capable of inhibiting the expression or activity of GP88.
A further object of the invention is to provide methods for treating diseases associated with a defect in GP88 quantity or activity such as but not limited to cancer in mice or humans.
Another object of the invention is to provide methods for determining the susceptibility of a subject to diseases associated with a defect in GP88 expression or action.
Yet another object of the invention is to provide methods for measuring susceptibility to GP88 antagonizing therapy.
Yet another object of the invention is to provide methods, reagents, and kits for the in vitro and in vivo detection of GP88 and tumorigenic activity in cells.
Additional objects and advantages of the invention will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by the practice of the invention.
To achieve the objects and in accordance with the purpose of the invention, as embodied and properly described herein, the present invention provides compositions for diagnosis and treatment of diseases such as but not limited to cancer in which cells exhibit an altered expression of GP88 or altered response to GP88.
Use of the term “altered expression” herein means increased expression or overexpression of GP88 by a factor of at least two-fold, and at times by a factor of 10 or more, based on the level of mRNA or protein as compared to corresponding normal cells or surrounding peripheral cells. The term “altered expression” also means expression which became unregulated or constitutive without being necessarily elevated. Use of the terms increased or altered “response” to GP88 means a condition wherein increase in any of the biological functions (e.g., growth, differentiation, viral infectivity) conferred by GP88 results in the same or equivalent condition as altered expression of GP88.
Use of the term “GP88” herein means epithelin/granulin precursor in cell extracts and extracellular fluids, and is intended to include not only GP88 according to the amino acid sequences included in
, which are of mouse and human origins, but also GP88 of other species. In addition, the term also includes functional derivatives thereof having additional components such as a carbohydrate moiety including a glycoprotein or other modified structures.
Also intended by the term GP88 is any polypeptide fragment having at least 10 amino-acids present in the above mentioned sequences. Sequences of this length are useful as antigens and for making immunogenic conjugates with carriers for the production of antibodies specific for various epitopes of the entire protein. Such polypeptides are useful in screening such antibodies and in the methods directed to detection of GP88 in biological fluids. It is well known in the art that peptides are useful in generation of antibodies to larger proteins (7). In one embodiment of this invention, it is shown that peptides from 12-19 amino-acids in length have been successfully used to develop antibodies that recognize the full length GP88.
The polypeptide of this invention may exist covalently or non-covalently bound to another molecule. For example, it may be fused to one or more other polypeptides via one or more peptide bonds such as glutathione transferase, poly-histidine, or myc tag.
The polypeptide is sufficiently large to comprise an antigenetically distinct determinant or epitope which can be used as an immunogen to reproduce or test antibodies against GP88 or a functional derivative thereof.
One embodiment includ
A & G Pharmaceutical, Inc.
Dickstein , Shapiro, Morin & Oshinsky, LLP
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