The invention provides the genomic sequence of GSSP-2, GSSP-2 cDNAs and GSSP-2 polypeptdes. Further the invention provides polynucleotides including biallelic markers derived from the GSSP-2 gene and from genomic regions flanking the gene. This invention also provides polynucleotides and methods suitable for genotyping a nucleic acid molecule containing sample for one or more biallelic markers of the invention. Further, the invention provides methods to detect a statistical correlation between a biallelic marker allele and a phenotype and/or between a biallelic marker haplotype and a phenotype. The invention also concerns methods and compositions for killing neoplastic cells or inhibiting neoplastic cell growth. In particular, the present invention concerns cell proliferation arresting/inhibiting and apoptosis/necrosis inducing compositions and methods for the treatment of tumors. The present invention is directed to novel polypeptides and to nucleic acid molecules encoding those polypeptides.