BIOCHIMIE, 1978, 60, 1221-1233. Revue Cell surface glycoproteins and Kenneth M. YAMADA * and Jacques POUYSSEGUR<>. (31-7-1978). malignant transformation. Centre de Biochimie, Universit~ de Nice, Pare Valrose, 0603~ Nice, France. I. Introduction. (;ell surface glycoproteins are thought to play important roles in cell adhesion, cell-cell reco- gnition, uptake of nutrients, and growth control [previous reviews include refs. 1-6]. A number of recent reports have identified individual glyco- proteins involved in some of these events, parti- cularly in nlalignant transformation. In order to organize this rapidly expanding literature, we have divided this review into three major sec- tions. Section II will be descriptive : after briefly smnniarizing the alterations in cell behavior that occur after malignant transformation, we shall describe in detail the many accompanying chan- ges in individual cell surface proteins. Section III will discuss two general approaches that have provided nieans to analyze the causal relation- ships of these changes, and that have started to provide a unified picture of the mechanisms of transformation, (A) the isolation and reconstitu- tion of cell surface components and (B) the isola- tion of mutants defective in specific cellular func- tions. Finally, sections IV and V will present a current, but tentative, cause-effect schenia for ma- lignant transformation, and will briefly discuss areas for future research. II. Specific alterations after transformation. A. ALTEI/EI) CELLULAR PROPERTIES. Transformation of fibroblastic cells in vitro by oncogenic viruses and carcinogens has provided valuable model systems by which to analyze the process of malignancy [7, 8]. A number of cellu- lar properties are found to be altered after trans- 0 1"o whom all correspondence shoald be addressed. (*) Permanent address of K.M.Y. is Laboratory of Molecular Biologg, National Cancer Institute, Bethesda, MD. 2001/~ U.S.A. formation [7-37] (table I). It is important to note that not all of these changes are found in all trans- formed cells, and that exceptions or lack of inves- tigations of a large number of transformants call each of these characteristics of transfornIed cells into question as markers for transformation [38- 47]. Nevertheless, these alterations frequently ac- conIpany transformation, and the mechanisms of each have been intensively investigated. B. ALTERE1) CELL SURFACE GLYCOPROTEINS. The amounts of several uleulbrane-associated proteins, the glycosylation of glycoproteins, and the types of secreted proteins are often altered after transformation (table II). These changes are also not always found in all transformed cells, for reasons that remain to be elucidated. In the fol- lowing sections, each of these protein alterations and their suggested relationships to the alterations in cell functions after transformation will be re- viewed. 1. Decreased [ibroneclin. Several years ago, a number of laboratories dis- covered that a niajor cell surface protein that was readily labeled by radioactive or imnmnological surface labeling techniques was decreased or ab- sent after transformation (reviewed in refs. 3, 48-50). In subsequent years, further work has shown that although this protein, cellular fibro- nectin (also known as LETS, CSP, or galactopro- tein a), is usually decreased after transformation, there are several exceptions. In 12 of 89 transfor- med cell lines, fibronectin is not obviously de- creased [50I ; niany of these exceptions are found in spontaneous in vitro transformants [3, 51]. Re- cent work suggests that decreases in cell surface fibronectin may be associated nlore with the ca- pacity of cells to metastasize than with their ini- tial capacity to form tumors after injection into inmmnosuppressed animals [52]. The decreases in cell surface fibronectin after transformation appear to result from a combina- tion of decreased biosynthesis, increased proteo- 84