The spread (metastasis) of prostate cancer (CaP) is associated with extraordinary pain, in some cases, paraplegia (due to bone metastasis), and eventually death. At the time of initial diagnosis, if urologists could know more exactly which clinically localized CaPs are likely to metastasize in the future and hence present with a poor prognosis, they could design more effective treatment and improve outcome. Existing tools such as PSA measurement or evaluation of tumor architecture (Gleason score) provide a ¿ball-park¿ estimate of the prognosis for CaP patients. Tests or markers that determine the aggressiveness of the tumor, and thereby accurately predict the prognosis for CaP patients, could help the clinicians to make appropriate treatment decisions. If these prognostic markers are also involved in pathways that regulate CaP growth and metastasis, treatments targeted at these markers could prevent metastasis and improve survival. Our laboratory has identified two such molecules, hyaluronic acid (HA) and hyaluronidase (HAase).
HA is a gel-like sugar polymer that aids tumor metastasis. Small fragments of HA stimulate growth of new blood vessels (angiogenesis), which is critically important for tumor growth and metastasis. HAase is an enzyme that degrades HA into small angiogenic fragments. Using CaP (and bladder cancer) cells and tissues, my laboratory was the first to unequivocally establish a link between HAase and cancer and to identify the tumor-derived HAase (HYAL1). We found that both HA and HAase levels are elevated in CaP tissues (three- to eightfold) when compared to normal (NAP) and benign (BPH) prostate tissues and that HYAL1 is expressed in CaP tissues and cells. The presence of angiogenic HA fragments in high-grade CaP (Gleason >= 7) tissues indicated the functional involvement of HA and HYAL1 in CaP progression. When we stained NAP, BPH, and CaP tissues to localize HA and HYAL1 using specific reagents, we found that while the increased HA is localized in the host cells that surround the tumor (i.e., stroma), the HYAL1 exclusively resides in the tumor cells. In preliminary studies, the HA and HYAL1 staining results predicted CaP progression (i.e., recurrence and metastasis) with 86' accuracy. When CaP cells were made to stop producing HAase by genetic engineering (i.e., HYAL1-antisense transfection), their growth and invasive function (a measure of metastatic ability) were significantly reduced. Thus, blocking HAase production in CaP (anti-HAase therapy) may inhibit angiogenesis (by preventing angiogenic HA fragment production) and growth/metastasis, and it could be used in CaP treatment. We found that VERSA-TL 502 (sodium polystyrene sulfonate), a water soluble, nontoxic possible contraceptive agent, inhibits both HAase activity produced by CaP cells and their proliferation.
The overall objectives of this study are to establish the prognostic capability of HA and HYAL1 for CaP and to evaluate the possibility of an anti-HAase therapy as a treatment for CaP. We hypothesize that both HA and HYAL1 are independent predictors of CaP prognosis (i.e., recurrence, metastasis, and survival). We also hypothesize that HYAL1 type HAase affects CaP progression by controlling the expression of genes that function in CaP growth and metastasis. We have designed three specific aims to test these hypotheses.
In the first aim, we will examine whether the HA and HYAL1 staining intensity (i.e., weak or strong) and the staining pattern (i.e., focal or diffuse) in archival CaP tissues can be used to predict prognosis for CaP patients on whom 7- to 10-year follow-up information is available. The prognostic capability of HA and HYAL1 staining will be compared to the prognostic information obtained from existing clinical/pathologic parameters. In the second aim, we will take two approaches to evaluate the effect of HYAL1 on CaP growth and progression. In the first approach, using immunologically tolerant mice, we will compare tumor-take rate, growth, and metastasis of CaP cells that have been made to stop HAase production (by HYAL1-antisense cDNA transfection) to that of the parent CaP cells that produce HAase. In the second approach, we will test the effectiveness of anti-HAase therapy in CaP treatment by testing the efficacy of VERSA-TL 502, a nontoxic HAase inhibitor, to inhibit the growth and metastatic ability of CaP cells in cell culture and in animal models. In the third aim, we will study the mechanism by which HYAL1 may control CaP growth and metastasis. We will make a pair-wise comparison of the differences in gene expression among the following: (1) parent CaP cells and HYAL1-antisense transfectant, (2) CaP tissues containing high and low levels of HYAL1, and (3) CaP cells either treated or untreated with VERSA-TL 502. The gene expression will be compared using a technique of cDNA microarray analysis. In studying this differential gene expression, special emphasis will be on growth- and metastasis-related genes, which might be regulated by HYAL1.
This investigation could establish HA and HYAL1 as accurate prognostic markers that help clinicians in making individualized treatment selections for CaP patients. The study would reveal whether an anti-HAase therapy, preferably involving a synthetic HAase inhibitor (e.g., VERSA-TL 502), could be a new therapeutic avenue of improving treatment for clinically localized and metastatic CaP.