IntroductionNatural killer (NK) cells are cytotoxic and cytokine-producing lymphocytes, involved in the immune defense against viral infections and tumors. 1 Their homeostasis is regulated by cytokines and membrane associate receptors able to inhibit or activate cellular programs. 2 The inhibitory receptors are well characterized and described extensively in several reviews. [3][4][5] Triggering of NK cells depends largely on NK receptor member D of the lectinlike receptor family (NKG2D) and natural cytotoxicity receptors (NCRs): NKp46, NKp44, NKp30. 6,7 NCRs are involved in the recognition of several tumor cell lines, although their ligands remain elusive. 6 NKG2D recognizes the MHC (major histocompatibility complex) class I chain-related (MIC) protein A (MICA) and B (MICB); both are nonclassic class I molecules. The UL16-binding proteins (ULBP1-3 or RAET1 proteins; ULBP1-3 in this paper) are the second group of NKG2D ligands in humans. MICs are expressed during virus infection or cell transformation; ULBP expression in fresh tumor cells is essentially unknown; only long-term cultured in vitro cell lines have been looked at so far. [8][9][10] Cytotoxic T lymphocytes (CTLs) and interferons (IFNs) have a key role in tumor progression and tumor "immune-editing process." 11 MHC class I molecule loss is a frequent event in tumor progression and could prevent CTL recognition. However, theoretically, NK cells could recognize MHC class I-defective tumors, according with the "missing self hypothesis." 12 So far, only in mouse models NK cells were demonstrated to destroy in vivo lymphoma and melanoma tumors with reduced MHC class I expression and/or with high levels of activating target structures. [13][14][15] Even though almost 30 years ago human NK cells were discovered for their in vitro antitumor cytotoxicity, we still have little information concerning the regulation of their antitumor activity in vivo or ex vivo. 16,17 Therefore, several questions remain to be addressed to understand the antineoplastic potential of human NK lymphocytes:1. HLA class I molecules are reported to be down-regulated during solid tumor progression. 18 19,20 Other hematopoietic-derived cells can stimulate NK lymphocytes as described for dendritic cells (DCs). 21 The B-cell membrane-associated proteins CD40 and CD1 regulate natural killer cell cytotoxicity. [22][23][24][25] Furthermore, NK lymphocytes are specifically activated after bone marrow graft but not by other tissue transplantations. 26 They localize in lymph nodes and spleen, mainly in B-cell follicles and in the marginal zone. 27 Blood, spleen, and bone marrow are the anatomic districts where the highest number and activity of NK cells are present. 1 Taking together these considerations, hematologic malignancies (B-cell-derived tumors in particular) could be considered an appealing system to investigate the potential role of NK cells in the control of tumor progression.Multiple myeloma (MM) is a plasma cell-derived tumor. It is characterized by accumulation of plasma cells in th...

Germline mutations of the tumour suppressor gene BRCA1 are involved in the predisposition and development of breast cancer and account for 20 -45% of all hereditary cases. There is an increasing evidence that these tumours are characterised by a specific phenotype and pattern of gene expression. We have hypothesised that differences in chemosensitivity might parallel molecular heterogeneity of hereditary and sporadic breast tumours. To this end, we have investigated the chemosensitivity of the BRCA1-defective HCC1937 breast cancer cell line, and the BRCA1-competent MCF-7 (hormone-sensitive) and MDA-MB231 (hormoneinsensitive) breast cancer cell lines using the MTT assay. The 50% inhibitory concentration (IC 50 ) for the individual compounds were derived by interpolate plot analysis of the logarithmic scalar concentration curve after a 48 h exposure. HCC1937 cells were significantly (Po0.005) more sensitive to cisplatin (CDDP) (IC 50 : 30-40 mM) compared with MCF-7 (IC 50 : 60-70 mM) and MDA-MB231 (IC 50 : 90 -100 mM) cells. On the other hand, BRCA1-defective breast cancer cells were significantly less sensitive to doxorubicin (Dox) (IC 50 : 45-50 mM) compared with MCF-7 (IC 50 : 1-5 mM) and MDA-MB231 (IC 50 : 5-10 mM) (Po0.02), as well as to paclitaxel (Tax) (IC 50 : 42 mM for HCC1937, 0.1 -0.2 mM for MCF-7 and 0.01 -0.02 mM for MDA-MB231) (Po0.001). Full-length BRCA1 cDNA transfection of BRCA1-defective HCC1937 cells led to the reconstituted expression of BRCA1 protein in HCC1937/ WT BRCA1-derived cell clone, but did not reduce tumour cell growth in soft agar. BRCA1 reconstitution reverted the hypersensitivity to CDDP (Po0.02), and restored the sensitivity to Dox (Po0.05) and Tax (Po0.001), compared with parental HCC1937 cells. Taken together, our findings suggest a specific chemosensitivity profile of BRCA1-defective cells in vitro, which is dependent on BRCA1 protein expression, and suggest prospective preclinical and clinical investigation for the development of tailored therapeutical approaches in this setting.

The phosphatidyl-inositol 3 kinase (PI3k)/ Akt pathway has been implicated in childhood acute lymphoblastic leukemia (ALL). Because rapamycin suppresses the oncogenic processes sustained by PI3k/Akt, we investigated whether rapamycin affects blast survival. We found that rapamycin induces apoptosis of blasts in 56% of the bone marrow samples analyzed. Using the PI3k inhibitor wortmannin, we show that the PI3k/Akt pathway is involved in blast survival. Moreover, rapamycin increased doxorubicin-induced apoptosis even in nonresponder samples. Anthracyclines activate nuclear factor B (NF-B), and disruption of this signaling pathway increases the efficacy of apoptogenic stimuli. Rapamycin inhibited doxorubicin-induced NF-B in ALL samples.

Bisphosphonates (BPs) are an emerging class of drugs mostly used in the palliative care of cancer patients. We investigated the in vitro activity of the most potent antiresorptive BP, zoledronic acid (ZOL), on the growth and survival of three human pancreatic cancer (PC) cell lines (BxPC-3, CFPAC-1 and PANC-1). Pancreatic cancer frequently has a dysregulated p21 ras pathway and therefore appears to be a suitable target for BPs that interfere with the prenylation of small GTP-binding proteins such as p21 ras . We found that ZOL induces growth inhibition (IC 50 :10 -50 mM) and apoptotic death of PC cells. The proapoptotic effect was correlated to cleavage/ activation of caspase-9 and poly(ADP)-ribose polymerase, but not of caspase-3. Moreover, we studied the p21 ras signalling in cells exposed to ZOL and detected a reduction of p21 ras and Raf-1 content and functional downregulation of the terminal enzyme ERK/ MAPkinase and of the pKB/Akt survival pathway. Finally, we observed that ZOL induces significant cytoskeletal rearrangements. In conclusion, we demonstrated that ZOL induces growth inhibition and apoptosis on PC cells and interferes with growth and survival pathways downstream to p21 ras . These findings might be relevant for expanding application of BPs in cancer treatment.