Reversal of cathepsin D routing modulation in MCF-7 breast cancer cells expressing antisense insulin-like growth factor II (IGF-II)

Selective induction of apoptosis in MCF7 cancer-cell by targeted liposomes functionalised with mannose-6-phosphate

Liposomes are versatile platforms to carry anticancer drugs in targeted drug delivery; they can be surface modified by different strategies and, when coupled with targeting ligands, are able to increase cellular internalisation and organelle-specific drug delivery. An interesting strategy of antitumoral therapy could involve the use of lysosomotropic ligand-targeted liposomes loaded with molecules, which can induce lysosomal membrane permeabilization (LMP), leakage of cathepsins into the cytoplasm and subsequent apoptosis. We have previously demonstrated the ability of liposomes functionalised with a mannose-6-phosphate to reach lysosomes; in this research we compare the behaviour of M6P-modified and non-functionalised liposomes in MCF7 tumour cell and in HDF normal cells. With this aim, we first demonstrated by Western blotting the overexpression of mannose-6-phosphate/insulin-like growth factor (M6P/IGF-II) receptor in MCF7. Then, we prepared calcein-loaded liposomes and we revealed the increased uptake of M6P-functionalised liposomes in MCF7 cells respect to HDF cells by flow cytometry analysis. Finally, we loaded functionalised and not functionalised liposomes with N-hexanoyl-d-erythro-sphingosine (C6Cer), able to initiate LMP-induced apoptosis; after having studied the stability of both vesicles in the presence of serum by Dynamic Light Scattering and Spectrophotometric turbidity measurements, we showed that ceramide-loaded M6P-liposomes significantly increased apoptosis in MCF7 with respect to HDF cells.

Tumor-targeted intracellular delivery of anticancer drugs through the mannose-6-phosphate/insulin-like growth factor II receptor

Tumor-targeting of anticancer drugs is an interesting approach for the treatment of cancer since chemotherapies possess several adverse effects. In the present study, we propose a novel strategy to deliver anticancer drugs to the tumor cells through the mannose-6-phosphate/insulin-like growth factor receptor (M6P/IGF-IIR) which are abundantly expressed in several human tumors. We developed a drug carrier against M6P/IGF-II receptor by modifying human serum albumin (HSA) with M6P moieties. M6P-HSA specifically bound and internalized into M6P/IGF-IIR-expressing B16 melanoma cells as demonstrated with radioactive studies and anti-HSA immunostaining. In vivo, M6P-HSA rapidly accumulated in subcutaneous tumors in tumor and stromal components after an intravenous injection. To demonstrate the application of M6P-HSA as a drug carrier, we coupled doxorubicin to it. Dox-HSA-M6P conjugate could release doxorubicin at lysosomal pH and showed M6P-specific binding and uptake in tumor cells. In vitro, a short exposure with Dox-HSA-M6P induced killing of tumor cells, which could be blocked by excess M6P-HSA. In vivo, Dox-HSA-M6P distributed to tumors and some other organs while free doxorubicin distributed to all organs but slightly to tumors. In B16 tumor-bearing mice, Dox-HSA-M6P significantly inhibited the tumor growth whereas an equimolar dose of free doxorubicin did not show any anti-tumor effect. In addition, targeted doxorubicin did not show any side-effects on liver and kidney function tests, body weight and blood cell counts. In conclusion, M6P-HSA is a suitable carrier for delivery of anticancer drugs to tumors through M6P/IGF-IIR. Improved antitumor effects of the targeted doxorubicin by M6P-HSA suggest that this novel approach may be applied to improve the therapeutic efficacy of anticancer drugs.

IGF binding proteins (IGFBPs) and regulation of breast cancer biology

The IGFBP family comprises six proteins with high affinity for the IGFs. Changes in the balance of the components of the IGF system may contribute to the progression of breast cancer. In tumours the abundance of IGFBPs relates to the estrogen receptor status and their production in the breast is controlled by hormones, principally estrogen and progesterone. Important interactions occur between IGFBPs and key growth regulators such as TGF-beta, PTEN and EGF which are reviewed. The conflicting observations between the effects of IGFBPs on the risk of breast cancer, in particular IGFBP-3, obtained from epidemiology studies in comparison to in vivo observations are highlighted and potential explanations provided. The functional activity of IGFBPs can also be affected by proteolysis, phosphorylation and glycosylation and the implications of these are described. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of their cellular actions. IGFBPs can affect cell function in an IGF-dependent or independent manner. The key mechanisms underlying the intrinsic actions of the IGFBPs are still in debate. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs and IGFBP proteases, but also by these factors delivered from the circulation. Finally, the therapeutic potential of IGFBPs-2 and -3 are considered together with key questions that still need to be addressed.

Differential effect of proIGF-II and IGF-II on resveratrol induced cell death by regulating survivin cellular localization and mitochondrial depolarization in breast cancer cells

Insulin-like growth factor II (IGF-II) plays a pivotal role in fetal and cancer development by signaling through the IGF-I and insulin receptors and activating the estrogen signaling cascade. We previously showed that precursor IGF-II (proIGF-II, the predominant form expressed in cancer) and not mature IGF-II (mIGF-II) blocks resveratrol (RSV) (a phytoalexin/anticancer agent)-induced cell death in MCF-7 cells. We hypothesize that proIGF-II regulates antiapoptotic proteins and/or the mitochondria to inhibit RSV actions and promote cell survival. This study examines the effect of mIGF-II and proIGF-II on survivin expression and mitochondrial polarization in response to RSV. RSV inhibits survivin expression and stimulates mitochondrial depolarization, caspase 7 activation and cell death. These effects were completely blocked by the addition of proIGF-II. RSV treatment had no effect on transfected MCF-7 cells constitutively expressing proIGF-II, while IGF-II siRNA transfection decreased survivin levels. Our results provide new insights for the potential use of proIGF-II as target for new anticancer therapies.

Expression of insulin-like growth factor-2 receptors on EL4 lymphoma cells overexpressing growth hormone

In the present study, we report the upregulation of functional IGF-2Rs in cells overexpressing growth hormone (GH). EL4 lymphoma cells stably transfected with an rGH cDNA overexpression vector (GHo) exhibited an increase in the binding of (125)I-IGF-2 with no change in the binding affinity compared to vector alone controls. An increase in the expression of the insulin-like growth factor-2 receptor (IGF-2R) in cells overexpressing GH was confirmed by Western blot analysis and IGF-2R promoter luciferase assays. EL4 cells produce insulin-like growth factor-2 (IGF-2) as detected by the reverse transcription-polymerase chain reaction (RT-PCR); however, no IGF-2 protein was detected by Western analysis. The increase in the expression of the IGF-2R resulted in greater levels of IGF-2 uptake in GHo cells compared to vector alone controls. The data suggest that one of the consequences of the overexpression of GH is an increase in the expression of the IGF-2R.

The effects of retinoic acid on the insulin-like growth factor axis in primary tissue culture from hyperparathyroidism

BACKGROUND

The importance of the IGF system in HPT has been previously demonstrated. Additionally, the role of vitamin A in HPT has been reported. Retinoic acid (RA), a derivative of vitamin A, is a ligand for the IGF II receptor (IGF2R). We have evaluated the interactions of RA with the IGF system in a primary parathyroid cell culture model.

MATERIALS AND METHODS

Primary cell cultures were prepared from nine patients. Following adhesion, the cells were transferred to serum-free medium and dosed once with growth factors +/- RA for 96 hours. Proliferation was assessed by measuring tritiated thymidine incorporation.

RESULTS

Compared with the control group (100%), both IGF I and II increased DNA synthesis significantly. Retinoic acid significantly reduced the basal DNA synthesis to 82.2% +/- 4.2% compared with control (P < 0.05). Retinoic acid x10(-5) M completely abrogated the proliferative actions of IGF II (70.2% +/- 9.7%, P < 0.05) but had no significant effect on the IGF I response (P > 0.05). To evaluate the role of IGF2R or IGFBPs in mediating the actions of RA, the IGF II analogs [Leu27]IGF II (10-20-fold reduced IGF I receptor affinity) and des(1-6) IGF II (lower IGFBP binding affinity) were used. The IGF II inhibitory effect of RA was enhanced in the presence of analogs [Leu27]IGF II (P = 0.052) but not with des(1-6)IGF II (P > 0.05), compared with wild-type IGF II.

CONCLUSIONS

These data implicate a novel antiproliferative role for RA in enhancing the pericellular clearance of IGF II via the IGF2R preventing ligand activation of the IGF I receptor. This may have broader implications for RA effects in other tumors.

Insulin-like growth factor II mediates resveratrol stimulatory effect on cathepsin D in breast cancer cells

Cathepsin D (CD) is an enzyme that promotes breast cancer. CD is stored intracellularly; however, we demonstrated that IGF-II promotes CD secretion in estrogen receptor positive (ER+) breast cancer cells. We also showed that resveratrol (RSV) stimulates IGF-II in ER(+) breast cancer cells. Thus, we designed this study to determine whether RSV regulates CD in MCF-7, T47D (ER+) breast cancer cells as well as in Hs578t (cancer) and MCF-10A (normal) ER - cell lines. RSV (10(- 6) M) increased CD and IGF-II secretion in ER+ but not ER - cells. RSV treatment (10(- 4) M) inhibited CD in ER+ but not in ER - cells. Transfection of ER - cells with proIGF-II increased CD secretion. RSV (10(- 6) M) modulates CD secretion through IGF-II while RSV (10(- 4) M) inhibits CD in ER+ but not ER - cells. Regulation of CD by RSV represents a novel mechanism by which RSV may protect against breast cancer.

The potentials of MS-based subproteomic approaches in medical science: the case of lysosomes and breast cancer

Because of the great number of women who are diagnosed with breast cancer each year, and though this disease presents the lowest mortality rate among cancers, breast cancer remains a major public health problem. As for any cancer, the tumorigenic and metastatic processes are still hardly understood, and the biochemical markers that allow either a precise monitoring of the disease or the classification of the numerous forms of breast cancer remain too scarce. Therefore, great hopes are put on the development of high-throughput genomic and proteomic technologies. Such comprehensive techniques should help in understanding the processes and in defining steps of the disease by depicting specific genes or protein profiles. Because techniques dedicated to the current proteomic challenges are continuously improving, the probability of the discovery of new potential protein biomarkers is rapidly increasing. In addition, the identification of such markers should be eased by lowering the sample complexity; e.g., by sample fractionation, either according to specific physico-chemical properties of the proteins, or by focusing on definite subcellular compartments. In particular, proteins of the lysosomal compartment have been shown to be prone to alterations in their localization, expression, or post-translational modifications (PTMs) during the cancer process. Some of them, such as the aspartic protease cathepsin D (CatD), have even been proven as participating actively in the disease progression. The present review aims at giving an overview of the implication of the lysosome in breast cancer, and at showing how subproteomics and the constantly refining MS-based proteomic techniques may help in making breast cancer research progress, and thus, hopefully, in improving disease treatment.

Insulin-like growth factor binding proteins (IGFBPs) in breast cancer

The IGFBP family comprises six proteins with high affinity for the IGFs and several lower affinity IGFBP-related proteins. Their production in the breast is controlled by hormones, other local regulators and in tumors relates to the estrogen receptor status. Their functional activity can also be affected by various post-translational modifications. The IGFs are generally present at levels far in excess of that required for maximal receptor stimulation, and the IGFBPs are critical regulators of cellular action. IGFBPs can affect cell function in an IGF-dependent or independent manner. IGF bioactivity locally in the breast is influenced not only by local tissue expression and regulation of IGFs, IGFBPs, and IGFBP proteases, but also by these factors delivered from the circulation. Changes in the balance of the components of the IGF system may lead to a disruption of tissue homeostasis.

Exhaustive mining of EST libraries for genes differentially expressed in normal and tumour tissues

A four-step procedure for the efficient and systematic mining of whole EST libraries for differentially expressed genes is presented. After eliminating redundant entries from the EST library under investigation (step 1), contigs of maximal length are built upon each remaining EST using about 4 000 000 public and proprietary ESTs (step 2). These putative genes are compared against a database comprising ESTs from 16 different tissues (both normal and tumour affected) to determine whether or not they are differentially expressed (step 3; electronic northern). Fisher's exact test is used to assess the significance of differential expression. In step 4, an attempt is made to characterise the contigs obtained in the assembly through database comparison. A case study of the CGAP library NCI_CGAP_Br1.1, a library made from three (well, moderately, and poorly differentiated) invasive ductal breast tumours (2126 ESTs in total) was carried out. Of the maximal contigs, 139 were found to be significantly (alpha = 0.05) over-expressed in breast tumour tissue, while 13 appeared to be down-regulated.