The American Cancer Society expects more than 20,000 new cases of MM in the US in 2010. The median age at diagnosis is 69 years for men and 72 years for women (it rarely occurs before 40 years) and the median survival is 5 years (2). Multiple myeloma (MM) is a malignancy characterized by clonal proliferation and accumulation of terminally differentiated plasma B cells that produce immunoglobulin. The malignant plasma cells are found in the bone marrow (BM) and extramedullary locations (1). Currently chemotherapy induces complete tumor regression in about 50% of patients (1, 3), but the eventual outcome is the development of drug resistance and death. Thus, the need for more efficacious treatments is apparent.
The introduction of novel drugs such as thalidomide, lenalidomide, and bortezomib (Bor) that are thought to target specific intracellular pathways and affect cellular interactions with the tumor microenvironment, has aided in the treatment of MM especially in management of elderly patients (1,3). Nonetheless, although the recent advances in hematological diseases and especially in MM have prolonged survival and led to higher rates of remission, arguably the course of the disease has not fundamentally changed since the 1960s, when autologous hematopoietic stem cell transplantation (AHSCT) was first recommended as a standard treatment in patients that were suitable candidates for the procedure. The frontline treatment for MM is AHSCT, but the outcome is favorable only in younger patients where it increases the rate of complete remission and prolongs event-free survival compared with conventional chemotherapy (4). Thus, pharmacologic interventions are the only option for the majority of patients who are older.
During the last ten years, intriguing insights into the molecular mechanisms underlying the progression of MM were obtained and successfully translated into more effective therapeutics, such as the proteasome inhibitors. The ubiquitin-proteasome pathway degrades intracellular proteins, interacts with the cell cycle and apoptosis, and has an important function in almost all cellular events (5,6). The U.S. Food and Drug Administration (FDA) granted approval for the proteasome inhibitor bortezomib (PS-341; VELCADE®) for the treatment of multiple myeloma in May 2003. This was the first approval of a drug targeting the ubiquitin-proteasome pathway. Since then the FDA also has approved bortezomib for treatment of mantle cell lymphoma. Several U.S. Pat. Nos. 5,780,454; 6,297,217; 6,617,317; and 6,747,150, disclose (and each of which are incorporated herein by reference) the use of bortezomib for treatment of cancer (7-10).
The development of drug resistance frequently causes bortezomib to become ineffective in treatment of multiple myeloma and the drug also displays problematic off-target adverse effects (11,12). Combinations of bortezomib with other therapeutics are being tested to develop regimens that will overcome drug resistance and reduce the occurrence of adverse side effects (13-15).
Bortezomib (Bor) is a synthetic peptide boronate that is a reversible proteasome inhibitor. Several other classes of compounds that inhibit the proteasome have been developed that include several irreversible inhibitors (5,6). Salinosporamide A (NPI-0052) is a natural product that is an irreversible proteasome inhibitor that has been the subject of several U.S. Pat. Nos. 7,842,814; 7,511,156; and 7,691,896 (16-18). Synergy in animal models of multiple myeloma was shown for the combination of salinosporamide A and lenalidomide (19). Carfilzomib (PR-171) is an irreversible proteasome inhibitor. Carfilzomib is a synthetic epoxomycin analog that was previously disclosed in U.S. Pat. No. 7,417,042 by Smyth and Laidig (20). Three of the irreversible proteasome inhibitors, salinosporamide A, carfilzomib, and CEP-18770 (a bortezomib analog), are being tested in clinical trials.
Bor also has shown promising activity in some types of solid tumors, such as combination studies in non-small cell lung cancer (21-25). Other studies including clinical trials of Bor have indicated potential benefit in breast (25), gastrointestinal cancer (26,27), and thyroid cancer (28,29).
Galectin-3C (Gal-3C) is an N-terminally truncated form of the human carbohydrate binding protein, galectin-3. Galectin-3 is involved in cancer cell adhesive properties, metastatic and invasive potentials (30-33), tumor growth, neoplastic transformation, and apoptosis (34-36). Galectin-3 is a member of the galectin family that is defined based on sequence homology within the carbohydrate recognition domain (CRD) and a characteristic affinity for -galactosides (37,38). Galectin-3 is unique among the galectins because in addition to the carboxy-terminal CRD it has an amino-terminal domain that is critical for multivalent behavior. Alone the carboxy-terminal CRD lacks hemagglutination activity and the cooperative binding that are characteristics of the intact lectin. The amino-terminal domain enables the CRD to cross-link carbohydrate-containing ligands on cell surfaces and in the extracellular matrix and, thus, to modulate cell adhesion and signaling (39-43).
Galectin-3 is thought to participate in regulation of the inflammatory state of various immune cells. Several studies indicate that it plays a novel regulatory role in the B cell compartment (44-46) including PCs (47). Hoyer et al. found stage-specific expression during B-cell development (48). Highest galectin-3 levels were observed in the long-lived naive and memory B cells, and lowest were in germinal center and plasma B cells. Nonetheless, high level galectin-3 levels were observed in the neoplasms that derive from these cells-diffuse large B-cellymphoma, primary effusion lymphoma, and MM (48).
The expression of galectin-3 in cancer has been the subject of many studies. Among those cancers in which galectin-3 is overexpressed are non-small cell lung cancer (49), gastrointestinal cancer (50, 51, 52, Miyazaki, 2002 #2994, 53, 54), thyroid cancer (55-57), and ovarian cancer (58). The gene expression level of galectin-3 in three CCC cell lines was over threefold higher than that of ovarian serous adenocarcinoma cell lines. Knock-down of galectin-3 expression in clear cell carcinoma (CCC) of the ovary using small interfering RNA induced increased apoptosis induced by cisplatin, suggesting that galectin-3 expression may contribute to cisplatin-resistance in ovarian CCC (59).
The truncated galectin-3 (Gal-3C) disclosed in the present invention consists of 143 carboxy-terminal amino acid residues of human galectin-3. Gal-3C retains carbohydrate binding ability but lacks the amino-terminal domain and, therefore, is expected to act as a dominant negative inhibitor of galectin-3 by preventing its homophilic cross-linking that promotes cell adhesion and consequent survival signals (60). The amino acid sequence of the galectin-3C, that is produced by exhaustive digestion with collagenase, and that is designated as SEQ ID NO: 1, is as follows: gap agplivpynl plpggvvprm litilgtvkp nanrialdfq rgndvafhfn prfnennrrv ivcntkldnn wgreerqsvf pfesgkpfki qvlvepdhfk vavndahllq ynhrvkklne isklgisgdi ditsasytmi (SEQ ID NO: 1)
The amino acid sequence of the intact recombinant human galectin-3 described by Oda et al. (61) is designated herein as SEQ ID NO: 2, and its sequence is as follows: madnfslhda lsgsgnpnpq gwpgawgnqp agaggypgas ypgaypgqap pgaypgqapp gayhgapgay pgapapgvyp gppsgpgayp ssgqpsapga ypatgpygap agplivpynl plpggvvprm litilgtvkp nanrialdfq rgndvafhfn prfnennrrv ivcntkldnn wgreerqsvf pfesgkpfki qvlvepdhfk vavndahllq ynhrvkklne isklgisgdi dltsasytmi (SEQ ID NO: 2)
Previously Gal-3C inhibited tumor growth and metastasis in a mouse model of human breast cancer and showed no evidence of adverse side effects (60). U.S. Pat. No. 6,770,622 to Jarvis et al. discloses the use of galectin-3C as set forth in SEQ ID No. 1 to treat cancer, to reduce tumor size, and to reduce metastasis (62).