Knock-down of Sorcin Induces Up-regulation of MDR1 in HeLa Cells

Abstract

In our previous study, the MDR1/Pglycoprotein-overexpressing multidrug resistant subline, Hvr100-6, was established from the human cervical carcinoma cell line HeLa-Ohio (HeLa) by stepwise exposure to an anti-microtubule agent, vinblastine sulfate, a typical substrate of MDR1. Their gene and protein expression profiles were analyzed herein, and 148 genes were identified to be differentially expressed by cDNA microarray analysis. The up-regulation of sorcin, a soluble resistance-related calcium-binding protein of 22 kDa, was confirmed in Hvr100-6 cells by the proteome analysis. To clarify the relationship between MDR1 and sorcin, HeLa cells were treated with small interfering RNAs (siRNAs) targeted for theirs mRNAs. The siRNA for MDR1 mRNA resulted in its decrease by 86% and 61% on the days 1 and 2 after the treatment, whereas the expression level of sorcin mRNA was not changed. On the other hand, the siRNA for sorcin mRNA suppressed its expression by 80-90% on days 1-3 after the treatment. Interestingly; suppression of sorcin induced a more than 3-fold increase in the expression level for MDR1 mRNA. An efflux function of MDR1 evaluated with using rhodamine 123 as a probe showed a tendency to be increased in HeLa cells treated with siRNA for sorcin, compared with that in the cells treated with scramble siRNA. The activity and the expression of caspase-3 in the sorcin knock-down HeLa cells were relatively higher than those in the cells treated with scramble siRNA. Thus, we demonstrated that sorcin might be a partial suppressor of MDR1 expression. Furthermore, the present study suggested that sorcin repressed apoptosis via dysfunction of caspase-3.

Sorcin Induces a Drug-Resistant Phenotype in Human Colorectal Cancer by Modulating Ca2+ Homeostasis

“…Some evidence suggests that sorcin may be responsible for inducing MDR in human tumors (17)(18)(19)(20)(21)(22)(23), but no information is available on the specific function of the 22 kDa isoform in CRC drug resistance. Thus, pRC-or 22 kDa sorcin-HCT-116-stable transfectants ( Supplementary Fig.…”

“…19) and CHOP regimen in diffuse large B-cell lymphoma (20). Other reports suggest a correlation between the expression of sorcin and the MDR1/P-glycoprotein: it has been shown that sorcin knockdown induces the upregulation of MDR1 in HeLa cells (21); by contrast, a direct correlation between sorcin and MDR1 expression and a role of sorcin in inducing a MDR phenotype has been observed in human leukemia and gastric carcinoma cells (22,23). Finally, recent studies in oral squamous cell carcinoma, NSCLC, and acute myeloid leukemia suggest that sorcin may be responsible for drug resistance and poor prognosis (19,24,25).…”

“…Because the above studies suggest an involvement of the 22 kDa sorcin isoform in the cytoprotective pathways of human cancer cells (17)(18)(19)(20)(21)(22)(23), without providing a more in-depth explanation of its function, and considering that we previously showed that only the mitochondrial isoform of sorcin interacts with TRAP1 and is crucial for its antiapoptotic function (11), we became interested in studying the expression of 22 kDa sorcin in human CRC and in characterizing its role in the drugresistant phenotype of this malignancy.…”

Quantitative proteomic analysis to discover potential diagnostic markers and therapeutic targets in human renal cell carcinoma

“…The level of mRNA for galectin-1 was measured by the quantitative real time RT-PCR method as described previously [13,14]. Forward primers, reverse primers and TaqMan probes are listed in Table 2.…”

Overexpression of sorcin results in multidrug resistance in gastric cancer cells with up-regulation of P-gp

“…The overexpression of sorcin genes may just be coincidental with the amplification of MDR (21). Other conflicting results suggested that sorcin might be independently involved in mediating MDR (22)(23)(24).…”