RNA interference-directed caveolin-1 knockdown sensitizes SN12CPM6 cells to doxorubicin-induced apoptosis and reduces lung metastasis

Abstract

Human renal cell carcinoma (HRCC) is characterized by a high level of resistance to all treatment modalities. Therefore, the investigation of global gene expression in HRCC might help understand its biologic behavior and develop treatment strategies. Using cDNA microarray analysis, we initially compared gene expression profiles between HRCCs and adjacent normal tissues, and found that 87 were up-regulated and 127 genes were down-regulated. Next, a subset of genes, twofold differentially expressed, were validated by Northern blotting. Unexpectedly, caveolin-1, a gene reported to be a tumor suppressor gene, was found to be up-regulated in HRCC tissues. Expression level of caveolin-1 in SN12CPM6 (high metastatic clone) was higher than in SN12C (low metastatic clone), and SN12CPM6 was more resistant to doxorubicin (DXR) than SN12C. Caveolin-1 gene was slightly induced in surviving SN12C cells after DXR treatment. Furthermore, SN12CPM6-siCav1 cells, which were transfected with siRNA of cavelon-1 gene, were more sensitive to DXR, compared to SN12CPM6, but reduction of caveolin-1 gene expression did not affect tumor formation in subcapsule of kidney and lung metastasis. On the other hand, induction of caveolin-1 gene affected the production of lung metastasis under anti-cancer drug treatment: the incidence of pulmonary metastasis was significantly lower in SCID mice injected with SN12CPM6-siCav1 cells, and the number of pulmonary nodules decreased significantly (p = 0.0004). The above results together suggest that caveolin-1 may confer a growth advantage to cancer cells during DXR chemotherapy and surviving HRCC cells eventually might develop lung metastasis.

Caveolin-1 is a negative regulator of tumor growth in glioblastoma and modulates chemosensitivity to temozolomide

“…Perhaps our most notable finding, however, is that a substantial number of genes involved in the activation of apoptotic and cell death pathways are increased as a result of Cav-1 overexpression (TP53, MOAP1, CASP3, CASP9, BCL2L11, BAK1, BID among others). Although the role of Cav-1 in apoptosis is contentious, with reports indicating both pro- and anti-cell death roles, it may be possible that expression of Cav-1 promotes apoptotic activity in U-87MG cells by inhibiting the BIRC5 gene product, survivin, as is suggested here and in previous reports 41 - 45 . In support of these microarray data, we were able to demonstrate, at the protein level, silencing of ERK, AKT, mTOR, RPS6 and cyclin D1 pathways with corresponding activation and cleavage of the key apoptosis initiator caspase 3.…”

The Caveolin-1 Connection to Cell Death and Survival

“…These results point towards an anti-apoptotic role for Caveolin-1 in these cells. Also, pulmonary metastasis was reduced in SCID-mice injected with Caveolin-1 siRNA-transfected cells treated with doxorubicin, suggesting again that Caveolin-1 reduces sensitivity to chemotherapeutic agents both in vitro and in vivo [141]. Finally, Caveolin-1 knock-down in MDCK cells over-expressing the drug transporter protein BCRP (for breast cancer resistance protein) sensitizes the cells to the chemotherapeutic agent mitoxantrone, thus reducing cell proliferation [142].…”

The effect of liposomal size on the targeted delivery of doxorubicin to Integrin αvβ3-expressing tumor endothelial cells

“…In previous studies, the interaction of PEG-LP modified with CD13 with NGR was used to target the vasculature of GI-LI-N, HTLA-230 and IMR-32 neuroblastoma tumors [5], where the IC50 values for these cells to DOX were found to be 0.4M, 0.6 M and 0.02M, respectively [8,9]. Later, the recognition of Integrin v3 by RGD modified PEG-LP was used to target the vasculature of an SN12C renal cell carcinoma (RCC) [6]; where the EC50 value of the SN12C cells to DOX was found to be 50 ng/ml [10]. Additionally, NG2 Proteoglycan interacting TAASGVRSMH/LTLRWVGLMS [11], a membrane type-1 matrix metalloproteinase (MT1-MMP) interacting GPLPLR [12] and the APRPG ligand (the target receptor is unknown at present) [13] modified PEG-LPs were used to target the vasculatures of melanoma (B16F10), Colon 26 NL-17 and glioblastoma tumors, respectively.…”