Activity of MDI-301, a novel synthetic retinoid, in xenografts

MDI 301 suppresses myeloid leukemia cell growth in vitro and in vivo without the toxicity associated with all-trans retinoic acid therapy

MDI 301 is a novel 9-cis retinoic acid derivative in which the terminal carboxylic acid group has been replaced by a picolinate ester. MDI 301, a retinoic acid receptor-α - agonist, suppressed the growth of several human myeloid leukemia cell lines (HL60, NB4, OCI-M2, and K562) in vitro and induced cell-substrate adhesion in conjunction with upregulation of CD11b. Tumor growth in HL60-injected athymic nude mice was reduced. In vitro, MDI 301 was comparable to all-trans retinoic acid (ATRA) whereas in vivo, MDI 301 was slightly more efficacious than ATRA. Most importantly, unlike what was found with ATRA treatment, MDI 301 did not induce a cytokine response in the treated animals and the severe inflammatory changes and systemic toxicity seen with ATRA did not occur. A retinoid with these characteristics might be valuable in the treatment of promyelocytic leukemia, or, perhaps, other forms of myeloid leukemia.

Antitumoral effects of 9-cis retinoic acid in adrenocortical cancer

The currently available medical treatment options of adrenocortical cancer (ACC) are limited. In our previous meta-analysis of adrenocortical tumor genomics data, ACC was associated with reduced retinoic acid production and retinoid X receptor-mediated signaling. Our objective has been to study the potential antitumoral effects of 9-cis retinoic acid (9-cisRA) on the ACC cell line NCI-H295R and in a xenograft model. Cell proliferation, hormone secretion, and gene expression have been studied in the NCI-H295R cell line. A complex bioinformatics approach involving pathway and network analysis has been performed. Selected genes have been validated by real-time qRT-PCR. Athymic nude mice xenografted with NCI-H295R have been used in a pilot in vivo xenograft model. 9-cisRA significantly decreased cell viability and steroid hormone secretion in a concentration- and time-dependent manner in the NCI-H295R cell line. Four major molecular pathways have been identified by the analysis of gene expression data. Ten genes have been successfully validated involved in: (1) steroid hormone secretion (HSD3B1, HSD3B2), (2) retinoic acid signaling (ABCA1, ABCG1, HMGCR), (3) cell-cycle damage (GADD45A, CCNE2, UHRF1), and the (4) immune response (MAP2K6, IL1R2). 9-cisRA appears to directly regulate the cell cycle by network analysis. 9-cisRA also reduced tumor growth in the in vivo xenograft model. In conclusion, 9-cisRA might represent a promising new candidate in the treatment of hormone-secreting adrenal tumors and adrenocortical cancer.

Effects of a synthetic retinoid on skin structure, matrix metalloproteinases, and procollagen in healthy and high-risk subjects with diabetes

BACKGROUND

In diabetes, foot ulceration may result from increased skin fragility. Retinoids can reverse some diabetes-induced deficits of skin structure and function, but their clinical utility is limited by skin irritation. The effects of diabetes and MDI 301, a nonirritating synthetic retinoid, and retinoic acid have been evaluated on matrix metalloproteinases (MMPs), procollagen expression, and skin structure in skin biopsies from nondiabetic volunteers and diabetic subjects at risk of foot ulceration using organ culture techniques.

METHODS

Zymography and enzyme-linked immunosorbent assay were utilized for analysis of MMP-1, -2, and -9 and tissue inhibitor of metalloproteinase-1 (TIMP-1) and immunohistochemistry for type I procollagen protein abundance. Collagen structure parameters were assessed in formalin-fixed, paraffin-embedded tissue sections.

RESULTS

The % of active MMP-1 and -9 was higher and TIMP-1 abundance was lower in subjects with diabetes. Type 1 procollagen abundance was reduced and skin structural deficits were increased in diabetes. Three μM MDI 301 reduced active MMP-1 and -9 abundance by 29% (P < .05) and 40% (P < .05), respectively, and increased TIMP-1 by 45% (P = .07). MDI 301 increased type 1 procollagen abundance by 40% (P < .01) and completely corrected structural deficit scores. Two μM retinoic acid reduced MMP-1 but did not significantly affect skin structure.

CONCLUSIONS

These data indicate that diabetic patients at risk of foot ulceration have deficits of skin structure and function. MDI 301 offers potential for repairing this skin damage complicating diabetes.

Seliciclib (CYC202, R-roscovitine) enhances the antitumor effect of doxorubicin in vivo in a breast cancer xenograft model

We sought to determine whether seliciclib (CYC202, R-roscovitine) could increase the antitumor effects of doxorubicin, with no increase in toxicity, in an MCF7 breast cancer xenograft model. The efficacy of seliciclib combined with doxorubicin was compared with single agent doxorubicin or seliciclib administered to MCF7 cells and to nude mice bearing established MCF7 xenografts. Post-treatment cells and tumors were examined by cell cycle analysis, immunohistochemistry and real-time PCR. Seliciclib significantly enhanced the antitumor effect of doxorubicin without additional murine toxicity. MIB1 (ki67) immunohistochemistry demonstrated reduced proliferation with treatment. The levels of p21 and p27 increased after treatment with doxorubicin or seliciclib alone or in combination, compared to untreated controls. However, no changes in p53 protein (DO1, CM1), survivin or p53 phosphorylation (SER15) were observed in treated tumors compared with controls. In conclusion, the CDK inhibitor seliciclib (R-roscovitine) enhances the antitumor effect of doxorubicin in MCF7 tumors without increased toxicity with a mechanism that involves cell cycle arrest rather than apoptosis.

Functions of normal and malignant prostatic stem/progenitor cells in tissue regeneration and cancer progression and novel targeting therapies

This review summarizes the recent advancements that have improved our understanding of the functions of prostatic stem/progenitor cells in maintaining homeostasis of the prostate gland. We also describe the oncogenic events that may contribute to their malignant transformation into prostatic cancer stem/progenitor cells during cancer initiation and progression to metastatic disease stages. The molecular mechanisms that may contribute to the intrinsic or the acquisition of a resistant phenotype by the prostatic cancer stem/progenitor cells and their differentiated progenies with a luminal phenotype to the current therapies and disease relapse are also reviewed. The emphasis is on the critical functions of distinct tumorigenic signaling cascades induced through the epidermal growth factor system, hedgehog, Wnt/beta-catenin, and/or stromal cell-derived factor-1/CXC chemokine receptor-4 pathways as well as the deregulated apoptotic signaling elements and ATP-binding cassette multidrug transporter. Of particular therapeutic interest, we also discuss the potential beneficial effects associated with the targeting of these signaling elements to overcome the resistance to current treatments and prostate cancer recurrence. The combined targeted strategies toward distinct oncogenic signaling cascades in prostatic cancer stem/progenitor cells and their progenies as well as their local microenvironment, which could improve the efficacy of current clinical chemotherapeutic treatments against incurable, androgen-independent, and metastatic prostate cancers, are also described.

Thermographic assessment of tumor growth in mouse xenografts

In human breast tumors, a 1-2 degrees C increase in skin surface temperature is usually observed at the periphery; it has been proposed that this change is due to the hypervascularity and increased blood flow resulting from tumor-associated angiogenesis. Here we tested the hypothesis that thermal imaging might represent a useful adjunctive technique in monitoring the growth dynamics of human tumor xenografts. Xenografts were established in immunocomprised nude mice using MDA-MB-231 or MCF7 breast cancer cells. We exploited the inherent noncontact and noninvasive advantages of infrared thermography to detect skin surface temperature changes. Continuous thermographic investigation was performed to detect and monitor tumor growth in vivo and high resolution digital images were analyzed to measure the tumor temperature dynamics. In contrast to the skin temperature increases associated with human breast cancer, a consistent temperature decrease was found in the xenograft mice. In one case, a smaller secondary tumor, otherwise undetectable, was clearly evident by thermal imaging. The tumors were cooler than the surrounding tissue with a maximum temperature reduction of 1.5 degrees C for MDA-MB-231 tumor and 3 degrees C for MCF7 tumors observed on day 14. In addition, the temperature of the xenograft tumors decreased progressively as they grew throughout the observation period. It was demonstrated that thermographic imaging could detect temperature changes as small as 0.1 degrees C on the skin surface at an early stage of tumor development. The findings of the study indicate that thermographic imaging might have considerable potential in monitoring human tumor xenografts and their response to anticancer drugs.

MDI 301, a non-irritating retinoid, induces changes in human skin that underlie repair

Previous studies have demonstrated that all-trans retinoic acid (RA) increases collagen production and decreases matrix metalloproteinase (MMP) activity in organ-cultured human skin. Decreased MMP activity is associated with up-regulation of tissue inhibitor of metalloproteinase-1 (TIMP-1). These changes are accompanied by a hyperplastic response in the epidermis. Here we show that a synthetic picolinic ester-substituted retinoid (designated as MDI 301) has comparable effects to those of RA in regard to these activities. What makes these findings of interest is that RA also stimulates elaboration of several pro-inflammatory cytokines and up-regulates leukocyte adhesion molecules in organ-cultured skin. MDI 301 does not induce such changes or is much less active. In a past study we showed that while RA was irritating to the skin of topically treated hairless mice, MDI 301 was essentially non-irritating under the same conditions [Varani et al. (2003) Arch. Dermatol Res 295:255-262]. Taken in conjunction with the findings from the past study, the present data suggest that MDI 301 will be similar to RA in capacity to repair damaged skin, but will be effective under conditions that are not irritating. These findings, thus, suggest that retinoid efficacy and clinically relevant irritancy are not inextricably linked. Potential for efficacy under conditions in which irritation is not observed is a strong rationale for further development of MDI 301 as a skin-repair agent.