Matrix metalloproteinase inhibitor Ro 28-2653 in combination with estramustine: tumor-reducing effects on hormone-sensitive prostate cancer in rats

New Derivatives of N-Hydroxybutanamide: Preparation, MMP Inhibition, Cytotoxicity, and Antitumor Activity

Using a novel method of N-substituted succinimide ring opening, new N-hydroxybutanamide derivatives were synthesized. These compounds were evaluated for their ability to inhibit matrix metalloproteinases (MMPs) and their cytotoxicity. The iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide showed the inhibition of MMP-2, MMP-9, and MMP-14 with an IC50 of 1-1.5 μM. All the compounds exhibited low toxicity towards carcinoma cell lines HeLa and HepG2. The iodoaniline derivative was also slightly toxic to glioma cell lines A-172 and U-251 MG. Non-cancerous FetMSC and Vero cells were found to be the least sensitive to all the compounds. In vivo studies demonstrated that the iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide had low acute toxicity. In a mouse model of B16 melanoma, this compound showed both antitumor and antimetastatic effects, with a 61.5% inhibition of tumor growth and an 88.6% inhibition of metastasis. Our findings suggest that the iodoaniline derivative of N1-hydroxy-N4-phenylbutanediamide has potential as a lead structure for the development of new MMP inhibitors. Our new synthetic approach can be a cost-effective method for the synthesis of inhibitors of metalloenzymes with promising antitumor potential.

Discovery of small molecule inhibitors for the snake venom metalloprotease BaP1 using in silico and in vitro tests

Snakebites represent an important public health problem, with a great number of victims with permanent sequelae or fatal outcomes, particularly in rural, agriculturally active areas. The snake venom metalloproteases (SVMPs) are the principal proteins responsible for some clinically-relevant effects, such as local and systemic hemorrhage, dermonecrosis, and myonecrosis. Because of the difficulties in neutralizing them rapidly and locally by antivenoms, the search and design of small molecules as inhibitors of SVMPs are proposed. The Bothrops asper metalloprotease P1 (BaP1) is hereby used as a target protein and by High Throughput Virtual Screening (HTVS) approach, the free access virtual libraries: ZINC, PubChem and ChEMBL, were searched for potent small molecule inhibitors. Results from the aforementioned approaches provided strong evidences on the structural requirements for the efficient BaP1 inhibition such as the presence of the pyrimidine-2,4,6-trione moiety. The two proposed compounds have also shown excellent results in performed in vitro interaction studies against BaP1.

Tumor-infiltrating immune cells promoting tumor invasion and metastasis: existing theories

It is a commonly held belief that infiltration of immune cells into tumor tissues and direct physical contact between tumor cells and infiltrated immune cells is associated with physical destructions of the tumor cells, reduction of the tumor burden, and improved clinical prognosis. An increasing number of studies, however, have suggested that aberrant infiltration of immune cells into tumor or normal tissues may promote tumor progression, invasion, and metastasis. Neither the primary reason for these contradictory observations, nor the mechanism for the reported diverse impact of tumor-infiltrating immune cells has been elucidated, making it difficult to judge the clinical implications of infiltration of immune cells within tumor tissues. This mini-review presents several existing hypotheses and models that favor the promoting impact of tumor-infiltrating immune cells on tumor invasion and metastasis, and also analyzes their strength and weakness.

Focal degeneration of basal cells and the resultant auto-immunoreactions: a novel mechanism for prostate tumor progression and invasion

The development of human prostate cancer is believed to be a multistep process, progressing sequentially from normal, to hyperplasia, to prostatic intraepithelial neoplasia (PIN), and to invasive and metastatic lesions. High grade PIN has been generally considered as the direct precursor of invasive lesions, and the progression of PIN is believed to be triggered primarily, if not solely, by the overproduction of proteolytic enzymes predominately by cancer cells, which result in the degradation of the basement membrane. These theories, however, are hard to reconcile with two main facts: (1) only about 30% untreated PIN progress to invasive stage, while none of the current approaches could accurately identify the specific PIN or individuals at greater risk for progression, and (2) results from recent world-wide clinical trials with a wide variety of proteolytic enzyme inhibitors have been very disappointing, casting doubt on the validity of the proteolytic enzyme theory. Since over 90% of prostate cancer-related deaths result from invasion-related illness and the incidence of PIN could be up to 16.5-25% in routine or ultrasound guided prostate biopsy, there is an urgent need to uncover the intrinsic mechanism of prostate tumor invasion. Promoted by the facts that the basal cell population is the source of several tumor suppressors and the absence of the basal cell layer is the most distinct feature of invasive lesions, our recent studies have intended to identify the early alterations of basal cell layers and their impact on tumor invasion using multidisciplinary approaches. Our studies revealed that a subset of pre-invasive tumors contained focal disruptions (the absence of basal cells resulting in a gap greater than the combined size of at least three epithelial cells) in surrounding basal cell layers. Compared to their non-disrupted counterparts, focally disrupted basal cell layers had several unique features: (1) significantly lower proliferation; (2) significantly lower p63 expression; (3) significantly higher apoptosis; and (4) significantly higher leukocyte infiltration and stromal reactions. Compared to their counterparts distant from focal disruptions or overlying non-disrupted basal cell layers, epithelial cells overlying focal basal cell layer disruptions showed the following unique features: (1) significantly higher proliferation; (2) significantly higher expression of cell cycle control-, cell growth-, and stem cell-related genes; and (3) physical continuity with adjacent invasive lesions. Together, these findings suggest that focal basal cell layer disruptions could substantially impact the molecular profile and biological presentations of the overlying epithelial cells. Based on these and other findings, we have proposed that prostate tumor invasion is triggered by a localized degeneration of aged or injured basal cells and the resultant auto-immunoreactions. Our hypothesized steps for prostate tumor invasion include the following: (1) due to inherited or environmental factors, some patients contained cell cycle control- and renewal-related defects in the basal cell population that cause elevated basal cell degenerations; (2) the degradation products of degenerated basal cells or diffusible molecules of the overlying epithelial cells attract leukocyte infiltration; (3) leukocytes discharge their digestive enzymes upon the direct physical contact, resulting in a focal disruption in the basal cell layer, which leads to several focal alterations: (a) a focal loss of tumor suppressors and paracrine inhibitory function; (b) a focal increase of the permeability for growth-required nutrients and oxygen; (c) a focal increase of growth factors; (d) direct physical contact between epithelial and stromal cells; and (e) the exposure of the overlying epithelial cells directly to the stromal tissue fluid. These alterations individually or collectively stimulate or favor a clonal proliferation and stromal invasion of tumor progenitor or stem cells. Our hypothesis differs from the traditional theories in several aspects, including the triggering factor for the initiation of tumor invasion, the stage of tumor invasion, the cellular origin of invasive lesions, the significance of immunoreactive and stromal cells, and the potential approaches for early detection, treatment, and prevention of invasion. Our hypothesis represents a novel in vivo model as to the cellular mechanism leading to prostate tumor invasion. If confirmed, it could lead to a new direction to search for more effective approaches to combat prostate cancer. It could also have an immediate impact on patient care through improved pathologic evaluation of prostate tumor biopsies. More importantly, our hypothesis might be applicable, and significantly impact the detection, treatment, and prevention of other epithelium-derived tumors.

Enhanced inhibitory effect of the matrix metalloproteinase inhibitor Ro 28-2653 in combination with estramustine and etoposide on the prostate carcinoma in the rat Dunning orthotopic tumor model

PURPOSE

Therapeutic efficacy of the novel matrix metalloproteinase (MMP) inhibitor Ro 28-2653 has been shown in various models of different tumor entities. We hypothesized that the inhibitor effect of Ro 28-2653 on the tumor growth could be improved by combination with chemotherapeutic drugs and examined therefore the effect of Ro 28-2653 alone and in combination with etoposide or estramustine in the MatLyLu Dunning R-3327 rat tumor model characteristic for the androgen-independent prostate cancer (PCa).

METHODS

In vitro effects were estimated measuring the proliferation of MatLyLu cells incubated with the three agents alone or in combination using the XTT test. The in vivo effects of the agents alone or in combination were examined by measuring the tumor weight 18 days after tumor cell injection.

RESULTS

The proliferation rate was only inhibited by etoposide while that effect was increased in combination with Ro 28-2653 and estramustine. Ro 28-2653 reduced the tumor weight by 86%. That effect was significantly increased in combination with etoposide to 92%.

CONCLUSIONS

The inhibitory effect of the MMP inhibitor Ro 28-2653 on the tumor growth in the Dunning PCa model is enhanced by the standard chemotherapeutic drug etoposide. A combined application of both agents could be considered as potential tool to improve the therapy of patients with advanced PCa after failure of hormonal treatment.