Induction of a less aggressive phenotype in human colon carcinoma HCT116 cells by chronic exposure to HDAC inhibitor SAHA

Histone deacetylase inhibitors (HDACis) are anticancer molecules that epigenetically modulate cell functions. Chronic exposure of HCT116 colon cancer cells to SAHA has been investigated for a better understanding of resistance mechanisms but, surprisingly, a less aggressive tumor phenotype both in vitro and in vivo was obtained after exposure to increasing concentrations of SAHA. Indeed, HCT116/SAHA cells when injected into nude mice showed a reduced engraftment and growth with respect to HCT116 cells. This difference was not observed inoculating the cells into NOD/SCID mice that, differently from nude mice, lack NK activity, thus suggesting the involvement of the native immune response in impairment of HCT116/SAHA cell growth. In agreement with this result, a growing induction of NKG2D ligand expression, MICA and MICB, that are molecular mediators of NK cell killing, was confirmed in HCT116/SAHA chronically exposed to SAHA. A reduced clonogenic efficiency was also observed in HCT116/SAHA with respect to HCT116 cells. Interestingly, even after chronic exposure to SAHA, HCT116/SAHA cells developed only a moderate resistance to SAHA both in vitro and in vivo and they acquired a collateral sensitivity to anthracyclines. These results are of note and probably rely on the fact that, having simultaneously many different targets, HDACis would require many different mutations to display high resistance index. Moreover, to understand the molecular basis of HCT116/SAHA cell phenotype a gene expression profile of cancer genes was evaluated in HCT116 incubated with SAHA for 24 h and in HCT116/SAHA cells to identify selectively regulated genes.     

Legacy effect of high glucose on promoting survival of HCT116 colorectal cancer cells by reducing endoplasmic reticulum stress response

Patients with diabetes have increased risk of cancer and poor response to anti-cancer treatment. Increased protein synthesis is associated with endoplasmic reticulum (ER) stress which can trigger the unfolded protein response (UPR) to restore homeostasis, failure of which can lead to dysregulated cellular growth. We hypothesize that hyperglycemia may have legacy effect in promoting survival of cancer cells through dysregulation of UPR. Using HCT116 colorectal cancer cells as a model, we demonstrated the effects of high glucose (25 mM) on promoting cell growth which persisted despite return to normal glucose medium (5.6 mM). Using the Affymetrix gene expression microarray in HCT116 cells programmed by high glucose, we observed activation of genes related to cell proliferation and cell cycle progression and suppression of genes implicated in UPR including BiP and CHOP. These gene expression changes were validated in HCT116 cancer cells using quantitative real-time PCR and Western blot analysis. We further examined the effects of thapsigargin, an anti-cancer prodrug, which utilized ER stress pathway to induce apoptosis. High glucose attenuated thapsigargin-induced UPR and growth inhibition in HCT116 cells, which persisted despite return to normal glucose medium. Western blot analysis showed activation of caspase-3 in thapsigargin-treated cells in both normal and high glucose medium, albeit with lower levels of cleaved caspase-3 in cells exposed to high glucose, suggesting reduced apoptosis. Flow cytometry analysis confirmed fewer apoptotic cells under thapsigargin treatment in cells exposed to high glucose. Our results suggested that hyperglycemia altered gene expression involved in UPR with increased cell proliferation and facilitated survival of HCT116 cells under thapsigargin-induced ER stress by reducing the apoptotic response.     

Loss of XIAP sensitizes rosiglitazone-induced growth inhibition of colon cancer in vivo

Ligands for peroxisome proliferator-activated receptor gamma (PPAR gamma) possess anticancer properties. However, the efficacy of PPAR gamma ligands varies in different cancers. In colon cancer, the role of PPAR gamma and its ligands is controversial. We recently showed that downregulation of X-linked inhibitor of apoptosis protein (XIAP) could sensitize colon cancer cells to troglitazone, and 15-deoxy-D12,14-prostaglandin J2 (15-PGJ2) induced cell killing. In our study, we aimed to examine whether rosiglitazone, another more clinically relevant PPAR gamma ligand, has any synergistic anticancer effect with XIAP downregulation in colon cancer. Human colon cancer cell lines HCT116-XIAP(+/+) cells and HCT116-XIAP(-/-) cells were treated with various concentrations of rosiglitazone. The effects of rosiglitazone on cell proliferation, apoptosis and growth of xenograft colon cancers were studied. Rosiglitazone barely suppressed the growth and only very weakly induced apoptosis in HCT116 cells in vitro. Loss of XIAP did not sensitize HCT116 cells to rosiglitazone-induced growth inhibition or apoptosis. In vivo studies revealed that rosiglitazone strongly suppressed the growth of xenograft colon cancer, especially tumors derived from HCT116-XIAP(-/-) cells. The rosiglitazone-treated tumor had reduced expression of ki-67 and lowered mitotic rate. Downregulation of XIAP was associated with an impaired activation of PPAR gamma by its ligand. Rosiglitazone induced marked upregulation of PTEN in HCT116-XIAP(-/-) cells, as well as in xenograft tumors derived from HCT116-XIAP(-/-) cells. We concluded that rosiglitazone significantly suppresses the growth of xenograft colon cancer, and downregulation of XIAP sensitizes the xenograft tumors to rosiglitazone-induced tumor suppression in vivo via upregulation of PTEN.     

Wild-type p53 is not sufficient for serum starvation-induced apoptosis in cancer cells but accelerates apoptosis in sensitive cells

According to the conflicting growth signal model, cells that are driven to proliferate by certain oncogenes undergo apoptosis but not growth arrest upon withdrawal of growth factors. However, we found that the majority of human cancer cell lines continued to proliferate and did not undergo apoptosis following serum withdrawal. As an exeption, wild-type (wt) p53-expressing HCT116 human colon cancer cells underwent apoptosis within 24-36 h of serum deprivation. p53 degradation in human papilloma virus EG-expressing HCT116 cells led to enhanced survival that was not due to growth arrest. These results are consistent with a role for p53 in starvation-induced death in HCT116 cells. However, other cell lines did not undergo apoptosis despite their expression of wt p53. Thus, H460 cells (wt p53) were resistant to starvation-induced death but introduction of the adenovirus EIA oncoprotein induced p53 and also increased sensitivity to serum withdrawal. p53 was not stabilized by E1A and resistance to starvation-induced cell death was observed in E6-expressing H460 cells. These results suggest that although p53 contributes to starvation-induced apoptosis in sensitive (HCT116 and E1A-expressing H460) cancer cell lines, most cancer cells survived despite the presence of wt p53. We conclude that naturally selected human cancer cell lines suppress apoptosis due to conflicting growth signals.     

Tumor suppression by resistant maltodextrin,Fibersol-2

Resistant maltodextrin Fibersol-2 is a soluble and fermentable dietary fiber that is Generally Recognized As Safe (GRAS) in the United States. We tested whether Fibersol-2 contains anti-tumor activity. Human colorectal cancer cell line, HCT116, and its isogenic cells were treated with FIbersol-2. Tumor growth and tumorigenesis were studied in vitro and in vivo. Apoptotic pathway and generation of reactive oxygen species (ROS) were investigated. We discovered that Fibersol-2 significantly inhibits tumor growth of HCT116 cells by inducing apoptosis. Fibersol-2 strongly induces mitochondrial ROS and Bax-dependent cleavage of caspase 3 and 9, which is shown by isogenic HCT116 variants. Fibersol-2 induces phosphorylation of Akt, mTOR in parental HCT116 cells, but not in HCT116 deficient for Bax or p53. It prevents growth of tumor xenograft without any apparent signs of toxicity in vivo. These results identify Fibersol-2 as a mechanism-based dietary supplement agent that could prevent colorectal cancer development.     

c-FLIP: a key regulator of colorectal cancer cell death

c-FLIP is an inhibitor of apoptosis mediated by the death receptors Fas, DR4, and DR5 and is expressed as long (c-FLIP(L)) and short (c-FLIP(S)) splice forms. We found that small interfering RNA (siRNA)-mediated silencing of c-FLIP induced spontaneous apoptosis in a panel of p53 wild-type, mutant, and null colorectal cancer cell lines and that this apoptosis was mediated by caspase-8 and Fas-associated death domain. Further analyses indicated the involvement of DR5 and/or Fas (but not DR4) in regulating apoptosis induced by c-FLIP siRNA. Interestingly, these effects were not dependent on activation of DR5 or Fas by their ligands tumor necrosis factor-related apoptosis-inducing ligand and FasL. Overexpression of c-FLIP(L), but not c-FLIP(S), significantly decreased spontaneous and chemotherapy-induced apoptosis in HCT116 cells. Further analyses with splice form-specific siRNAs indicated that c-FLIP(L) was the more important splice form in regulating apoptosis in HCT116, H630, and LoVo cells, although specific knockdown of c-FLIP(S) induced more apoptosis in the HT29 cell line. Importantly, intratumoral delivery of c-FLIP-targeted siRNA duplexes induced apoptosis and inhibited the growth of HCT116 xenografts in BALB/c severe combined immunodeficient mice. In addition, the growth of c-FLIP(L)-overexpressing colorectal cancer xenografts was more rapid than control xenografts, an effect that was significantly enhanced in the presence of chemotherapy. These results indicate that c-FLIP inhibits spontaneous death ligand-independent, death receptor-mediated apoptosis in colorectal cancer cells and that targeting c-FLIP may have therapeutic potential for the treatment of colorectal cancer.     

p53 dependence and apoptosis in response to FP treatment with p53-transfected colon cancer cell lines by use of thin layer collagen gel

The combination of 5-fluorouracil (5-FU) plus Cisplatin (CDDP) (FP treatment) possesses synergistic cytotoxicity against colon cancer. The molecular mechanisms by which chemotherapeutic agents induce apoptosis have been clarified by identifying apoptosis-related genes such p53 and bcl-2. We previously established a new experimental technique in which cancer cells are distributed in thin collagen gel as 1 or 2 cell layers. additionally, we evaluated the efficacy and toxicity of FP treatment in the gastric and colon cancer cell lines, and examined the relationship between the response to FP treatment and apoptosis. In these results we reported transfection of normal p53 gene into p53 mutant and analyzed the impact of the p53 gene in a sensitivity test. In this study, we examined induced apoptosis in colon cancer cell lines and the status of p53 expression in response to treatment of HCT116, COLO320, SW480 and DLD1 with 5-FU alone, CDDP alone and FP treatment under flow cytometric analysis. Transfection of SW480 and DLD1 cells was performed to compare the chemosensitivity of naturally occurring mutant-type p53 SW480 and DLD1 cells with neo-transfected SW480 and DLD1 cells and transfected SW480 and DLD1 cells. Appreciable apoptosis was induced in HCT116 and COLO320 (p53 wild-type) but not in SW480 and DLD1 cells (p53 mutant-type). Transfected SW480 and DLD1 cells underwent significantly more apoptosis (p相似文献   

Selenomethionine induces p53 mediated cell cycle arrest and apoptosis in human colon cancer cells

While there is an increasing interest in selenium chemoprevention against human colon polyp recurrence and other cancers, the mechanism(s) by which these agents inhibit carcinogenesis are uncertain. Some of the proposed mechanisms include the inhibition of cytosine methyltransferases, carcinogen bioactivation, and inhibition of cyclooxygenase (COX). More recently, it has been suggested that selenium may exert growth inhibitory effects by activating p53. However, the molecular mechanisms of action of selenomethionine, an organoselenium compound present in selenized yeast and currently being investigated in human clinical trials for colon polyp prevention, are unclear. In the present study we tested the hypothesis that selenomethionine might affect colon cancer cell growth by p53 mediated apoptosis and/or cell cycle regulation. Four human colon cancer cell lines including HCT116 and RKO (wild type p53), HCT116-p53KO (isogenic control of HCT116 cells with p53 knocked out) and Caco-2 (mutant p53) were treated with 0-100 microM of selenomethionine for 24, 48 and 72 h. Cell viability rates were determined by the MTT assay. Cell cycle analysis was performed by flow cytometry and apoptosis measured by Annexin V-Cy5 staining. Expression of p53 protein was determined by Western blotting and immunofluorescence assays. All cell lines showed concentration and time dependent growth inhibition with selenomethionine, although HCT116 and RKO cells were the most sensitive to such treatments. Interestingly, although HCT116 and HCT116-p53KO are isogenic cell lines, selenomethionine caused a G2/M cell cycle arrest in HCT116 and RKO cells, but not in HCT116-p53KO cells. Similarly, both HCT116 and RKO demonstrated a significant increase in apoptosis (100-170%; p < 0.01) with 50-100 microM selenomethionine. Cell cycle arrest and apoptosis observed in HCT116 and RKO cell lines were accompanied by a marked increase in p53 protein expression following selenium treatment. These results clearly suggest that selenomethionine exerts p53 dependent growth inhibitory effects in colon cancer cells by inducing G2/M cell cycle arrest as well as apoptosis.     

Glutathione S-transferase pi1 promotes tumorigenicity in HCT116 human colon cancer cells

GSTP1 is a member of the glutathione S-transferase enzyme superfamily, which catalyzes the conjugation of electrophiles with glutathione in the process of detoxification. GSTP1 is widely overexpressed in colorectal cancer, from aberrant crypt foci to advanced carcinomas. Increased expression of GSTP1 is associated with multidrug resistance and a worse clinical prognosis. However, GSTP1-null mice have an increased risk of tumor formation. Thus, the biological function of GSTP1 in colorectal cancer biology remains speculative. In an effort to gain further insights into the role of GSTP1 in tumorigenesis, we disrupted the GSTP1 gene in HCT116 human colorectal cancer cells using targeted homologous recombination. We find that loss of GSTP1 resulted in impaired clonogenic survival and proliferation. Specifically, under growth-limiting conditions, (a) GSTP1 protected HCT116 cells from oxidative stress and associated apoptosis and (b) promoted mitogen-activated protein kinase-extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase-mediated G1-S cell cycle progression. In vivo, GSTP1 was critical for engraftment and growth of HCT116 tumor xenografts. These studies directly show that GSTP1 promotes clonogenic survival and proliferation in HCT116 human colon cancer cells.     

p21(Waf1/Cip1) and p53 are downstream effectors of protein kinase C delta in tumor suppression and differentiation in human colon cancer cells

We have previously demonstrated that the delta isoform of protein kinase C (PKCdelta) is importantly involved in cell growth inhibition and tumor suppression in colon cancer cells. To investigate further the activity and mechanism of action of PKCdelta, we have retrovirally transduced a PKCdelta cDNA in HCT116 human colon cancer cells. PKCdelta-overexpressing cells (HCT116/PKCdelta) were growth-inhibited, showed marked morphologic changes and underwent multinucleation and phenotypic changes characteristic of mitotic catastrophe. Compared to controls, HCT116/PKCdelta cells showed a highly attenuated tumorigenic profile and poor anchorage-independent growth. In addition, transfected cells established junction-coordinated intercellular communications, expressed cell surface microvilli and overexpressed the colon differentiation marker alkaline phosphatase. HCT116/PKCdelta cells also produced the 89 kDa, carboxy-terminal catalytic domain of PARP. In HCT116/PKCdelta cells, p21(Waf1/Cip1) and p53 were transiently upregulated for 48 hr after PKCdelta transduction. In a p21 null subline of HCT116 cells (HCT116/p21null), overexpression of PKCdelta did not affect tumorigenicity or differentiation, indicating that p21 is essential for the antitumorigenic activity of PKCdelta. Similarly, overexpression of PKCdelta caused no significant phenotypic changes in HCT116/E6 cells, an HCT116 subline in which the p53 protein is downregulated by the human papillomavirus E6 gene product. We conclude that overexpression of PKCdelta in human colon cancer cells induces multiple antineoplastic effects that depend on the activities of p21(Waf1/Cip1) and p53.     

TIP30基因对大肠癌细胞HCT116生物学特性的影响

目的通过构建基因真核表达载体分析TIP30对大肠癌细胞HCT116生物学特性的影响,为TIP30在大肠癌基因治疗中的应用提供依据。方法构建pCMV4-flag-TIP30真核表达载体并转染HCT116细胞,RT-PCR和Western blot检测TIP30基因表达,体外侵袭实验检测细胞侵袭能力,软琼脂实验检测细胞成瘤性。结果成功构建稳定表达TIP30的HCT116细胞模型,转染TIP30 的HCT116细胞增殖受抑,侵袭能力及克隆形成能力均减弱。结论大肠癌HCT116细胞TIP30过表达不仅能抑制其生长、诱导其凋亡,并能降低其侵袭、迁移能力,为TIP30基因治疗提供依据。     

Systemic treatment with the antidiabetic drug metformin selectively impairs p53-deficient tumor cell growth

The effect of the antidiabetic drug metformin on tumor growth was investigated using the paired isogenic colon cancer cell lines HCT116 p53(+/+) and HCT116 p53(-/-). Treatment with metformin selectively suppressed the tumor growth of HCT116 p53(-/-) xenografts. Following treatment with metformin, we detected increased apoptosis in p53(-/-) tumor sections and an enhanced susceptibility of p53(-/-) cells to undergo apoptosis in vitro when subject to nutrient deprivation. Metformin is proposed to function in diabetes treatment as an indirect activator of AMP-activated protein kinase (AMPK). Treatment with AICAR, another AMPK activator, also showed a selective ability to inhibit p53(-/-) tumor growth in vivo. In the presence of either of the two drugs, HCT116 p53(+/+) cells, but not HCT116 p53(-/-) cells, activated autophagy. A similar p53-dependent induction of autophagy was observed when nontransformed mouse embryo fibroblasts were treated. Treatment with either metformin or AICAR also led to enhanced fatty acid beta-oxidation in p53(+/+) MEFs, but not in p53(-/-) MEFs. However, the magnitude of induction was significantly lower in metformin-treated cells, as metformin treatment also suppressed mitochondrial electron transport. Metformin-treated cells compensated for this suppression of oxidative phosphorylation by increasing their rate of glycolysis in a p53-dependent manner. Together, these data suggest that metformin treatment forces a metabolic conversion that p53(-/-) cells are unable to execute. Thus, metformin is selectively toxic to p53-deficient cells and provides a potential mechanism for the reduced incidence of tumors observed in patients being treated with metformin.     

Altered expression of cell proliferation-related and interferon-stimulated genes in colon cancer cells resistant to SN38

Irinotecan is a topoisomerase I inhibitor widely used as an anticancer agent in the treatment of metastatic colon cancer. However, its efficacy is often limited by the development of resistance. We have isolated a colon carcinoma cell line, HCT116-SN6, which displays a 6-fold higher resistance to SN38, the active metabolite of irinotecan. In this paper, we studied the molecular mechanisms that cause resistance to SN38 in the HCT116-SN6 cell line. First, we analyzed proliferation, cell cycle distribution, apoptosis, topoisomerase I expression and activity in SN38-resistant (HCT116-SN6) and sensitive (HCT116-s cells). We showed that the SN38-induced apoptosis and the SN38-activated cell cycle checkpoints leading to G(2)/M cell cycle arrest were similar in both cell lines. Topoisomerase I expression and catalytic activity were also unchanged. Then, we compared mRNA expression profiles in the two cell lines using the Affymetrix Human Genome GeneChip arrays U133A and B. Microarray analysis showed that among the genes, which were differentially expressed in HCT116-s and HCT116-SN6 cells, 27% were related to cell proliferation suggesting that proliferation might be the main target in the development of resistance to SN38. This result correlates with the phenotypic observation of a reduced growth rate in HCT116-SN6 resistant cells. Furthermore, 29% of the overexpressed genes were Interferon Stimulated Genes and we demonstrate that their overexpression is, at least partially, due to endogenous activation of the p38 MAP kinase pathway in SN38 resistant cells. In conclusion, a slower cell proliferation rate may be a major cause of acquired resistance to SN38 via a reduction of cell cycle progression through the S phase which is mandatory for the cytotoxic action of SN38. This lower growth rate could be due to the endogenous activation of p38.     

p53 dependence of Fas induction and acute apoptosis in response to 5-fluorouracil-leucovorin in human colon carcinoma cell lines.

We examined the patterns of induction of apoptosis, Fas expression, and the influence of the status of the p53 tumor suppressor gene, in response to treatment of human colon carcinoma cell lines to 5-fluorouracil (FUra) combined with leucovorin (LV) under conditions of both DNA-directed (HT29, VRC5/c1, and RKO) and RNA-directed (HCT8 and HCT116) cytotoxicity. Acute apoptosis was induced in cell lines expressing wtp53 (RKO, HCT8, and HCT116), independent of the mechanism of FUra action. In HT29 cells that expressed mp53, apoptosis was a delayed event. Cell lines undergoing DNA-directed FUra cytotoxicity demonstrated marked accumulation of cells in S-phase (HT29 and RKO), whereas those lines undergoing RNA-directed cytotoxicity (HCT8 and HCT116) demonstrated marked cell cycle phase arrest in G2-M, both reversible by dThd. dThd partially protected HCT8 and HCT116 cells from FUra-LV-induced apoptosis but had no influence on FUra-LV-induced loss in clonogenic survival. In cells expressing wtp53, the Fas death receptor was induced in response to FUra-LV treatment. FUra-LV sensitized RKO cells to the anti-Fas monoclonal antibody CH-11 that was completely reversed by dThd, demonstrating the involvement of DNA damage in FUra-LV-induced, Fas-dependent sensitization to CH-11. In contrast, FUra-LV sensitized HCT116 cells to CH-11-induced apoptosis, which was not dThd reversible. Transduction of HT29 cells with Ad-wtp53 induced elevated Fas expression and sensitized the cells to FUra-LV-induced apoptosis. Data indicate that the presence of a wtp53 gene determines FUra-LV-induced Fas expression, the kinetics of FUra-LV-induced apoptosis and not the extent of apoptosis induced, both being independent of the mechanism of FUra action. Therefore, in colon carcinomas that express wtp53, the approach to sensitize tumors to Fas-mediated apoptosis may be further enhanced from the effect of FUra-LV in elevating Fas expression in a p53-dependent manner.     

Role of hMLH1 promoter hypermethylation in drug resistance to 5-fluorouracil in colorectal cancer cell lines

Loss of DNA mismatch repair (MMR) occurs in 10-15% of sporadic colorectal cancer, is usually caused by hMLH1 hypermethylation, and has been shown to confer resistance to various chemotherapeutic reagents, including 5-fluorouracil (5-FU). We tested the hypothesis that demethylation of the hMLH1 promoter in hypermethylated colorectal cancer cells would restore MMR proficiency and drug sensitivity to 5-FU. We used the MMR-deficient cell lines SW48, HCT116, HCT116+chr2 and the -proficient cell line HCT116+chr3. After treatment with the demethylating agent 5-Aza-2'-deoxycytidine (5 aza-dC), hMLH1 mRNA and protein expression were determined by RT-PCR and immunoblots. The methylation status for hMLH1 was investigated by methylation-specific PCR. Cells were subsequently treated with 5-FU and the growth characteristics ascertained by clonogenic assays. hMLH1 hypermethylation was reverted in SW48 cells 24 hr after treatment with 5 aza-dC and was accompanied by hMLH1 mRNA and protein reexpression. While 5 aza-dC alone did not affect the growth of SW48 cells, all other cell lines responded with a pronounced growth inhibition. 5-FU treatment strongly reduced the colony formation of HCT116+chr3 cells. These effects were significantly less in the MMR-deficient cells. Combined treatment of SW48 cells resulted in a similar growth pattern as seen in 5-FU only treated HCT116+chr3 cells. We demonstrate that in vitro resistance to 5-FU can be overcome by reexpression of hMLH1 protein through 5 aza-dC-induced demethylation in hypermethylated cell lines. Induction of the expression of methylated tumor suppressor or MMR genes could have a significant impact on the development of future chemotherapy strategies.     

Negative regulation of chemokine receptor CXCR4 by tumor suppressor p53 in breast cancer cells: implications of p53 mutation or isoform expression on breast cancer cell invasion

Chemokine receptor CXCR4 and its ligand CXCL12 are suggested to be involved in migration, invasion and metastasis of breast cancer cells. Mutation of the tumor suppressor gene p53 in breast cancer is associated with metastasis and aggressive clinical phenotype. In this report, we demonstrate that wild type but not the dominant-negative mutant (V143A) or cancer-specific mutants (R175H or R280K) of p53 repress CXCR4 expression. Recently described cancer-specific p53 isoform, Delta133p53, also failed to repress CXCR4 promoter activity. Short-interfering RNA-mediated depletion of p53 increased endogenous CXCR4 expression in MCF-7 breast cancer cells that contain wild-type p53. Basal CXCR4 promoter activity in HCT116 colon carcinoma cells deleted of p53 [HCT116(p53KO)] was 10-fold higher compared to that in parental HCT116 cells with functional wild-type p53. Deletion analysis of CXCR4 promoter identified a seven-base pair p53-repressor element homologous to cyclic AMP/AP-1 response (CRE/AP-1) element. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed binding of ATF-1 and cJun to the CRE/AP-1 element. The p53 rescue drug PRIMA-1 reduced CXCR4 mRNA and cell surface expression in MDA-MB-231 cells, which express R280K mutant p53. CP-31398, another p53 rescue drug, similarly reduced cell surface levels of CXCR4. PRIMA-1-mediated decrease in CXCR4 expression correlated with reduced invasion of MDA-MB-231 cells through matrigel. These results suggest a mechanism for elevated CXCR4 expression and metastasis of breast cancers with p53 mutations or isoform expression. We propose that p53 rescue drugs either alone or in combination with chemotherapeutic drugs may be effective in reducing CXCR4-mediated metastasis.