Antisense oligonucleotide intralesional therapy for human PC-3 prostate tumors carried in athymic nude mice

Antisense Oligonucleotides Targeting Angiogenic Factors as Potential Cancer Therapeutics

Cancer is one of the leading causes of death worldwide, and conventional cancer therapies such as surgery, chemotherapy, and radiotherapy do not address the underlying molecular pathologies, leading to inadequate treatment and tumor recurrence. Angiogenic factors, such as EGF, PDGF, bFGF, TGF-β, TGF-α, VEGF, endoglin, and angiopoietins, play important roles in regulating tumor development and metastasis, and they serve as potential targets for developing cancer therapeutics. Nucleic acid-based therapeutic strategies have received significant attention in the last two decades, and antisense oligonucleotide-mediated intervention is a prominent therapeutic approach for targeted manipulation of gene expression. Clinical benefits of antisense oligonucleotides have been recognized by the U.S. Food and Drug Administration, with full or conditional approval of Vitravene, Kynamro, Exondys51, and Spinraza. Herein we review the scope of antisense oligonucleotides that target angiogenic factors toward tackling solid cancers.

Differentiated prostatic antigen expression in LNCaP cells following treatment with bispecific antisense oligonucleotides directed against BCL-2 and EGFR

Antisense oligonucleotides (oligos) have been administered against in vivo and in vitro prostate cancer models employing LNCaP and PC-3 cell lines. While most oligos consist of a single mRNA binding site targeting a single gene product or those with sequence homology, our lab has developed bispecific oligos directed toward two unrelated proteins. In LNCaP cells, we initially identified bispecifics that increased the expression of prostate-specific membrane antigen (PSMA) while not affecting secreted prostate-specific antigen (PSA). We postulated that surface antigen expression is increased by bispecifics able to form double-stranded regions, acting as interferon (IFN-γ) inducers. In other systems, when induced, IFN-γ promotes cell surface antigen expression, including HLA and receptors for tumor necrosis factor. To test this hypothesis, we measured the effect of oligo treatment on both IFN-γ induction and the expression of another secreted product of differentiated prostate cells, prostatic acid phosphatase (PAP). This study initially evaluated the inhibition of in vitro propagating LNCaP cells employing mono- and bispecific oligos directed against bcl-2 (the second bispecific binding site was against the epidermal growth factor receptor). Employing RT-PCR, the expression of non-targeted proteins encoded by mRNA for PSMA, PSA, PAP, and IFN-γ was subsequently valuated. When LNCaP prostate tumor cells were incubated with oligos and compared to lipofectin-containing controls significant growth inhibition resulted. Employing RT-PCR, the levels of mRNA encoding PSMA were unexpectedly found to be elevated following treatment with the bispecific oligos but not with a monospecific directed solely against bcl-2. No differences were detected in mRNA levels encoding PSA following treatment with either oligo type. IFN-γ was significantly induced only by bispecific oligos, and PAP expression was similar to PSA. These data support the hypothesis that double strand-forming bispecific oligos induce IFN-γ that enhances cell surface PSMA expression. Expression of tumor-associated surface antigens could increase their recognition and targeting by immunologic defense mechanisms and increase the effectiveness of tumor vaccines.

Bax expression remains unchanged following antisense treatment directed against BCL-2

Antisense oligonucleotides (oligos) have been evaluated in both in vivo and in vitro prostate cancer models. Although most contain a single mRNA binding site, our laboratory has also evaluated bispecific types directed toward two proteins. This study evaluates the inhibition of in vitro propagating LNCaP cells employing mono- and bispecific oligos directed against bcl-2 [the second binding site was directed against the epidermal growth factor receptor (EGFR)]. Employing RT-PCR, the expression of two apoptosis regulating proteins, bcl-2 and non-targeted bax, was then evaluated. LNCaP prostate tumor cells were initially incubated for 24 h in the presence of oligos (6.25 μM) directed against bcl-2 and compared to lipofectin containing controls. Comparable and significant growth inhibition was produced by both mono- and bispecific forms. Employing RT-PCR to determine the expression of bcl-2, we found that the greatest amount of mRNA suppression approached 100% for each oligo type: monospecific MR4 (directed only against bcl-2), 100%; and bispecifics MR24 and MR42, 86 and 100%, respectively. We conclude, based upon both inhibition of in vitro growth and bcl-2 expression, that bispecific antisense oligos directed against EGFR and bcl-2 mRNAs are at least as effective as a monospecific directed solely toward bcl-2. In an effort to determine a compensatory response by cells evading apoptosis in the presence of bcl-2 suppression, the levels of mRNA encoding the non-targeted apoptosis activating protein bax were evaluated. Non-targeted protein suppression by these bispecifics has previously been demonstrated against prostate-specific membrane antigen (PSMA). However, in contrast to effects against bcl-2 and PSMA, no significant alteration in bax expression was produced by either oligo type. In LNCaP cells, bcl-2 suppression does not influence bax expression and, at least for this protein, there is no compensatory change in bax expression regulating apoptosis at this level. Identifying changes in the expression of proteins which regulate apoptosis is important if gene therapy targets bcl-2.

Increased prostate-specific membrane antigen expression in LNCaP cells following treatment with bispecific antisense oligonucleotides directed against bcl-2 and EGFR

Antisense oligonucleotides have been employed against in vivo and in vitro prostate cancer models. While most oligos consist of a single mRNA binding site, targeting a single gene product or others sharing sequence homology, our laboratory has developed bispecific oligos directed toward even unrelated proteins. This study evaluates the inhibition of in vitro propagating LNCaP cells employing mono- and bispecific oligos directed against bcl-2 [the second bispecific binding site was directed against the epidermal growth factor receptor (EGFR)]. Employing RT-PCR, the expression of non-targeted proteins encoded by mRNA for prostate-specific membrane antigen (PSMA) and prostate-specific antigen (PSA) were subsequently evaluated. When LNCaP prostate tumor cells were incubated with bispecific oligos (directed against bcl-2 and EGFR) and compared to lipofectin-containing controls significant growth inhibition resulted. In subsequent experiments, the levels of mRNA encoding PSMA were unexpectedly found to be elevated following treatment with the bispecific oligos but not with the monospecific directed solely against bcl-2. No differences were detected in mRNA levels encoding PSA following treatment with either mono- or bispecific oligos. Previously, we suggested that cell growth inhibition produced by some bispecifics could be attributed to complementary double-stranded regions formed by intra-strand base pairs. Double-stranded nucleic acids are known inducers of interferon, which promote expression of cell surface HLA type antigens. If induced, perhaps this cytokine also enhances PSMA expression, making prostate tumor cells a more recognizable target for cytotoxic T cells.

Treatment of prostate and breast tumors employing mono- and bi-specific antisense oligonucleotides targeting apoptosis inhibitory proteins clusterin and bcl-2

Antisense oligonucleotides (oligos) have demonstrated their efficacy in inhibiting the growth of prostate and breast tumor cells. Previous studies employed first generation, phosphorothioated, cDNA oligos synthesized complimentary to mRNA encoding transforming growth factor-alpha (TGF-alpha), epidermal growth factor receptor (EGFR), the anti-apoptosis protein bcl-2, and the androgen receptor (AR). In an effort to construct oligos with greater than one mRNA binding site, bi-specifics have been developed which target combinations of the above proteins, and these have been shown at least as effective as the mono-specific oligos from which their sequences were derived. While all bi-specifics have inhibitory effects, which can be enhanced by the combined administration of an additional chemotherapeutic agent, those bi-specifics which target bcl-2 and EGFR were reported to be the most effective. The experiments presented here are an effort to evaluate a new group of bi-specifics whose targets include the chaperone protein clusterin, whose expression is up regulated in many tumors and activity is known to inhibit apoptosis. Of particular interest were those bi-specifics constructed to target both clusterin and bcl-2 (also an apoptosis inhibitory protein). Cell lines targeted included both prostate LNCaP and PC-3, as well as the breast derived MCF-7. In order to identify agents which enhance oligo activity, but contribute less toxicity, oligos were tested both alone and in combination with either the immune inhibitor Rapamycin, or the chemotherapeutic (and more toxic) Taxol. Results indicate that bi-specifics targeting clusterin are statistically effective, and are similarly enhanced by Rapamycin, or Taxol. When bi-specifics including clusterin as a target, were tested against LNCaP and MCF-7 cells, the level of activity was intermediate between that of the mono-specific compounds tested separately. In experiments which compared both, bi-specifics which included a target for clusterin had inhibitory activity similar to the previously described bi-specifics directed towards bcl-2 and EGFR.

Combination chemotherapy employing bispecific antisense oligonucleotides having binding sites directed against an autocrine regulated growth pathway and bcl-2 for the treatment of prostate tumors

In previous studies we demonstrated that antisense oligonucleotides (oligos) against transforming growth factor-alpha (TGF-alpha [MR1]), its binding site the epidermal growth factor receptor (EGFR [MR2]), and the anti-apoptosis protein bcl-2 (MR4) are efficacious against prostate tumors. In recent reports we also describe how two of these mRNA directed binding sites can be synthesized sequentially within a single linear complementary strand and administered either in the presence or absence of additional therapeutic agents. In these continuing experiments "bispecific" oligo pairs were further evaluated in the presence or absence of Cytoxan, Taxol, or DES. One oligo pair recognized the binding sites for TGF-alpha and EGFR mRNA (TGF-alpha/EGFR [MR12] and EGFR/TGF-alpha [MR21]); another pair recognized binding sites for EGFR and bcl-2 (EGFR/bcl-2 [MR24] and bcl-2/EGFR [MR42]). Oligo pairs differ in their linear 5' to 3' binding site orientations, and were tested in vitro against PC-3 and LNCaP prostate tumor cell lines. Following cell attachment, incubations were for 2 days with the agents followed by 2 days in their absence. When tested against PC-3 cells and combined with LD50 Cytoxan, MR2, MR4, MR24, MR42 significantly inhibited 47.3, 45.7, 68.3, and 64.9%; with LD50 Taxol MR2, MR4, MR24, MR42 significantly inhibited 49.8, 45.8, 64.1, and 59.2%; and with LD50 DES MR2, MR4, MR24, MR42 significantly inhibited 66.6, 67.6, 64.3, and 67.2% respectively. Each agent significantly increased the inhibition produced by either oligo alone.LNCaP cells were also incubated with mono- and bispecific oligos in either the presence or absence of chemotherapeutics. MR2, MR4, MR24, MR42 produced significant inhibitions of 57.4, 58.4, 69.4, and 68.6% with LD50 Cytoxan; 70.4, 70.1, 73.6, and 74.0% with LD50 Taxol; and 49.8, 50.1, 59.6, and 53.9%, respectively with LD50 DES.A complete PC-3 experiment compared MR1, MR2, MR4, MR12, MR21, MR24 and MR42, in the presence of LD50 Cytoxan. Each oligo combined with Cytoxan significantly inhibited: MR1 by 51.0, MR2 by 55.0, MR4 by 58.0; MR12 by 56.0; MR21 by 61.1, MR24 by 65.5 and MR42 by 66.0%. Bispecifics directed against two different pathways, MR24, and MR42 were the most effective.A complete LNCaP experiment compared the same series of oligos also in the presence of LD50 Cytoxan. Each oligo combined with Cytoxan significantly inhibited: MR1 by 49.0, MR2 by 50.0, MR4 by 53.0; MR12 by 52.0; MR21 by 58.6, MR24 by 53.9 and MR42 by 58.0%.

Bispecific antisense oligonucleotides having binding sites directed against an autocrine regulated growth pathway and bcl-2 for the treatment of prostate tumors

Antisense oligonucleotides (oligos) against transforming growth factor-alpha (TGF-alpha) (MR1) and its binding site, the epidermal growth factor receptor (EGFR) (MR2), are efficacious against PC-3 and LNCaP prostate tumors. To enhance activity and aid in simultaneous delivery, "bispecific" 39-mer oligos were constructed containing portions of both MR1 and MR2 sequences. The first pair contained truncated sequences recognizing TGF-alpha and EGFR mRNA binding sites, about their respective AUG initiation codons. These bispecifics differ in their 5' to 3' tandem orientation (TGF-alpha/EGFR [MR12] and EGFR/TGF-alpha [MR21] sequences). A second pair was constructed having complementary sequences for EGFR and bcl-2 (EGFR/bcl-2 [MR24] and bcl-2/EGFR [MR42]). All bispecifics were tested in vitro against PC-3 and LNCaP prostate tumor cells, and compared to mono-specific oligos from which they were derived. The purpose of this study was: (1) to evaluate bispecific antitumor activity; (2) to identify dominant sequences; (3) to identify effects of binding site orientation; and (4) to determine whether bispecifics are more effective when targeting one versus different growth-dependent pathways. Comparisons were made between oligos tested against either PC-3 or LNCaP cells incubated for 2 d with the agents followed by 2 d in their absence. The first PC-3 cell experiment demonstrated that bispecific MR12 and MR21 oligos are at least as effective as their mono-specific counterparts and that the MR21 bispecific orientation is more effective than the MR1 mono-specific by 64% (p = 0.014). It also suggested that the sequence directed against EGFR contributed most to bispecific activity, particularly in the MR21 orientation. In a second PC-3 study a second bispecific pair of 37-mer oligos was constructed containing bases complementary to mRNA encoding EGFR and the apoptosis-associated protein bcl-2 (MR4). MR24 was constructed with the EGFR complementary site at the 5' end (EGFR/bcl-2), and MR42, containing the opposite orientation (bcl-2/EGFR). Each contained the dominant EGFR activity identified previously. MR1, MR2, MR4, MR12, MR21, MR24, and MR42 (1X and 2X in concentration) were cultured with cells and compared to controls. Each oligo significantly inhibited growth of PC-3 cells. MR42 was most effective and significantly better than MR1 (p = 0.0128), MR2 (p = 0.021), MR4 (p = 0.0002), and MR12 (p = 0.0032). 2X MR24 and 2X MR42 were better than their 1X concentration counterparts, but the differences were not significant. In a similar experiment MR1, MR2, MR4, MR12, MR21, MR24, and MR42 were cultured with LNCaP cells and compared to lipofectin-containing controls. Each oligo significantly inhibited the growth of LNCaP cells. Again, MR42 was most effective and significantly better than MR2 (p = 0.021) and MR4 (p = 0.038). MR24 was significantly better than MR2 (p = 0.048). Bispecific oligos are a significant advance in antisense technology and could play a role in treating prostate cancer, particularly if combined with traditional chemotherapeutics.

Treatment of MCF-7 breast cancer cells employing mono- and bispecific antisense oligonucleotides having binding specificity toward proteins associated with autocrine regulated growth and BCL-2

Antisense oligonucleotides (oligos) against transforming growth factor-alpha (TGF-alpha) (MR1) and its binding site, the epidermal growth factor receptor (EGFR) (MR2), are efficacious against the UACC 897 breast, PC-3 and LNCaP prostate, and T98G glioblastoma tumor lines in both in vitro and in vivo studies. Oligos against the anti-apoptosis protein bcl-2 (MR4) are also efficient against PC-3 and LNCaP tumors in similar in vitro experiments. To enhance activity, and also to introduce a derivative type of multifunctional oligo into this field, "bispecifics" were constructed containing two truncated complementary DNA sequences (from either MR1 or MR2) designed to bind targeted mRNA about their respective AUG initiation codons, and/or a similar sequence adjacent to the AUG site of mRNA encoding bcl-2. Tandem pairs of bispecifics were constructed: The first had complementary sequences for TGF-alpha and EGFR mRNA, but differed in 5' to 3' tandem orientation (TGF-alpha/EGFR [MR12] and EGFR/TGF-alpha [MR21] sequences); a second pair had binding sites associated with EGFR and bcl-2, also differing in orientation (EGFR/bcl-2 [MR24] and bcl-2/EGFR [MR42]). In studies targeting PC-3 and LNCaP cells, bispecifics demonstrated significant in vitro activity, and the second pair was significantly better than the original monospecifics. These studies are now extended to the MCF-7 breast cancer model in order to determine whether these particular bispecifics have similar anti-breast cancer activity and if they are significantly better than monospecific oligos from which they were derived. We conclude that bispecific oligos significantly inhibit MCF-7 growth, however, in contrast to results obtained with PC-3 and LNCaP, the monospecific oligos directed against EGFR and bcl-2 have significantly greater activity than the bispecifics targeting a combination of TGF-alpha, EGFR, or bcl-2. These data suggest that the relative activities of oligos, whether mono- or bispecific, change with tumor type. Bispecific oligos which target different proteins, possibly those which regulate estrogen utilization, may be more effective against MCF-7 cells and warrant additional investigation, particularly if co-administered with traditional chemotherapeutics.

Synthesis of branched antisense oligonucleotides having multiple specificities. Treatment of hormone insensitive prostate cancer

Antisense oligonucleotides (oligos) directed against transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR), have demonstrated in vitro and in vivo efficacy against both the PC-3 and LNCaP prostate tumor models. In an attempt to increase the efficiency of these oligos a new type of antisense compound called a bispecific oligo has been evaluated in vitro both alone and in combination with traditional chemotherapeutic agents. These bispecifics, which were first proposed in this journal in 2004, include binding sites for both TGF-alpha and EGFR along the same stretch of complementary DNA. Such bispecifics are able to deliver essentially two antisense activities in an equal molar ratio and can be directed against mRNA encoding proteins of different biochemical pathways. The first bispecifics were developed against two proteins regulating a single autocrine loop. Subsequent bispecifics have been developed which target both EGFR and the apoptosis regulating protein bcl-2. Bispecific activity of a single linear sequence oligo has already been shown to have efficacy. To further develop this multispecific approach, we now propose a branched antisense compound, again, having multiple binding site activities (to complementary sequenced mRNA). Active oligos would be attached to a fat soluble backbone which might enhance targeting and also intracellular entry, release and activity. Such a structure would also permit the customization of these branched forms to include oligos targeting specific proteins related to the growth of various tumor types. Problems associated with the development of antisense oligos have included both membrane solubility and specific targeting. By designing this branched form of antisense structure, multiple activities can be retained (added), solubility improved and delivery enhanced. Such a new formulation would include several antisense oligos covalently bound to and branching off from a lipid-like backbone. An elongated hydrocarbon chain would increase fat solubility and would permit oligo incorporation into nanoparticles or liposome derived delivery vehicles. Specific delivery of oligos could also be enhanced by the tendency of these nanoparticle or liposomal microbubbles to be disrupted under the influence of ultrasonic waves beamed at the targeted tissue.

Construction of a bispecific antisense oligonucleotide containing multiple binding sites for the treatment of hormone insensitive prostate tumors

Antisense oligonucleotides (oligos) have demonstrated efficacy for the treatment of various cancers, infectious diseases and metabolic disorders. While most studies have utilized single oligos either administered alone, or more recently in combination therapy with other drugs, some investigators have administered more than one oligo in a combined administration or have designed oligos which target multiple proteins (those which share mRNA sequence homology). Antisense oligos inhibit mRNA translation through complementary base pair binding, often about the AUG initiation codon. This inhibition is further enhanced through destruction of the mRNA:oligo hybrid by RNAse H. Construction of an oligo with multiple binding sites located about the respective mRNA initiation codons could simultaneously block translation of more than one protein, even those unrelated in sequence. Such binding could produce a complex mRNA:oligo hybrid more prone to degradation and clearance. Furthermore, such a formulation would increase oligo specific activity and cellular uptake, reduce toxicity, and stabilize at 1:1 the ratio between multiple oligo active sites which otherwise must be comparably delivered (in amount) and individually targeted. The activity of these newly constructed oligos could be tested in both in vitro and in vivo prostate tumor models, utilizing the hormone sensitive LNCaP and the hormone insensitive PC-3 lines. In vitro testing would evaluate oligos administered either alone or in combination with other chemotherapeutics. In vivo testing would administer the oligos to tumors carried in athymic nude mice by either intratumoral inoculation or by using a diffusion pump. Antisense oligos which target proteins associated with growth factors or their receptors, could have a role in the treatment of human prostate cancers when administered with hormone deprivation therapy, or against tumors which have already become hormone insensitive. In the later case, such treatment could form the basis of a second tier of therapy based upon growth factor deprivation.

Synergistic effects of combination therapy employing antisense oligonucleotides with traditional chemotherapeutics in the PC-3 prostate cancer model

Combination therapy including antisense oligonucleotides (ODNs) with traditional chemotherapeutic agents offers potential benefits by increasing the effectiveness of the chemotherapeutics, reducing their effective dosage, and simultaneously reducing toxicity. Previously we have reported that antisense ODNs specific for transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR) (MR1 and MR2, respectively), are effective against the PC-3 in vitro and in vivo prostate cancer models. In this series we evaluated these antisense ODNs in various combinations and treatment cycles with paclitaxel (Taxol), cyclophosphamide (Cytoxan), mitoxantrone, carboplatin, cisplatin, and oxaliplatin in order to identify synergistic effects.We found that when either of the ODNs were simultaneously administered with Taxol, no synergistic activity was noted. However, when sequentially administered in a series 1 d apart, a pretreatment with the ODN directed against TGF-alpha (6.64 microm) followed by Taxol (5 nm) had significantly (p <0.001) greater activity than these agents similarly administered in the reverse order or simultaneously. When Cytoxan was administered in sequence with both ODNs significantly increased growth inhibition was obtained compared to when Cytoxan was administered alone. A 1 d treatment of PC-3 cells with Cytoxan followed the next day with MR1 was significantly more effective (p <0.0001). The reverse order, a pretreatment with MR1 followed by Cytoxan, also resulted in significant additional inhibition (p=0.0004). Similarly sequenced, MR2 followed by Cytoxan, was also significantly more effective (p=0.0014) than Cytoxan treatment alone. For mitoxantrone, which was administered in combination therapy with ODNs: mitoxantrone with MR1 was significantly more inhibitory than the combination of both MR1 and MR2 ODNs (p=0.006) and also mitoxantrone administered alone (p=0.0012). Mitoxantrone administered with MR1 was not significantly different from mitoxantrone given in combination with MR2. Although mitoxantrone and MR2 was statistically (p=00015) more inhibitory than mitoxantrone alone, this combination was barely more effective (p=0.04) than the MR1 ODN administered alone.

Correlation between PSMA and VEGF expression as markers for LNCaP tumor angiogenesis

Our aim is the identification and correlation of changes in tumor-associated protein expression which results from therapy. LNCaP tumors, excised from nude mice treated either by orchiectomy or with the chemotherapeutic agent paclitaxel, were evaluated for the expression of proteins and receptors associated with growth, differentiation, and angiogenesis using immunohistologic procedures. Compared to untreated control tumors, both treatments reduced the expression of vascular endothelial growth factor (VEGF), prostate-specific membrane antigen (PSMA), prostate-specific antigen (PSA), androgen receptor (AR), and epidermal growth factor receptor (EGFR). The effect of paclitaxel treatment on AR expression was the most significant (P = .005). Of particular interest was identifying a significant correlation (P < .000801) between PSMA and VEGF expression regardless of treatment modality. These altered expressions suggest that PSMA may also be a marker for angiogenesis and could represent a target for deliverable agents recognizing either prostatic tumors or endothelial development. Cell surface PSMA would then present a unique target for treatment of patients early in their development of prostatic metastases.

Inhibition of PC-3 prostate cancer cell growth in vitro using both antisense oligonucleotides and taxol

Antisense oligonucleotides (oligos) directed against mRNA-encoding transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGFR) have demonstrated in vitro and in vivo efficacy against prostate cancer tumor models. However, many therapeutic agents have increased effectiveness when given in combination with other more established agents. We evaluated the effectiveness of two oligos (3.32 and 6.64 microM/L) known to have significant activity against the PC-3 prostate cell line in combination therapy with the chemotherapeutic agent paclitaxel (Taxol) (2.5 and 5.0 nm). Therapy was evaluated when oligos and Taxol were administered either as (1) single agents, (2) simultaneously in a combined therapy, or (3) sequentially, a form of combination therapy with both agents being administered in a series. We found that when either of the two oligos were given simultaneously with Taxol, no synergistic activity was noted. However, when sequentially administered in a series 1 d apart, a pretreatment with the antisense directed against TGF-alpha (6.64 microM/L) followed by Taxol (5 nm) had significantly greater activity than these agents similarly administered in the reverse order or simultaneously.>

Inhibition of LNCaP prostate tumor growth in vivo by an antisense oligonucleotide directed against the human androgen receptor

We have shown recently that a 15-mer phosphorothioate oligodeoxynucleotide (ODNas750/15) that hybridizes to the (CAG)n polyglutamine region of mRNA encoding human androgen receptor (AR) inhibits the expression of AR in LNCaP prostate cancer cells in vitro. This AR downregulation was accompanied by significant cell growth inhibition and reduced PSA secretion. In the present study we investigated the effects of this antisense AR ODN on prostate tumor growth in vivo using a mouse xenograft model. Via subcutaneously implanted diffusion pumps, either ODNas750/15 or a scrambled control sequence ODNsr750/15 was continuously administered into LNCaP tumor-bearing male nude mice for 7 weeks. Compared with untreated control animals, treatment with ODNas750/15 resulted in significant tumor growth inhibition. Retardation of tumor growth was also significant in castrated mice, whereas the scrambled control ODN did not exert any effects. No side effects such as loss of body weight were observed at any time of treatment. ODN treatment was well tolerated and, in contrast to castration, did not induce shrinkage of mouse prostates. Both AR expression in the tumor and PSA levels in mouse serum correlated with tumor size. However, we failed to demonstrate a correlation between tumor retardation and Ki-67 antigen expression and the number of apoptotic cells, respectively. Testing of antisense-treated LNCaP cells revealed that expression levels of other proteins that contain shorter polyglutamine sequence stretches such as HDAC2, TFIID, and c-jun were not affected. The present study demonstrates that downregulation of AR with antisense ODNas750/15 causes prostate tumor growth inhibition. These results further point out the important role of the AR in prostate tumors and support further testing of AR downregulation for treatment of prostate cancer.

TGF-alpha antisense gene therapy inhibits head and neck squamous cell carcinoma growth in vivo

Unlike normal mucosal squamous epithelial cells, head and neck squamous cell carcinomas (HNSCCs) overexpress TGF-alpha mRNA and protein which is required to sustain the proliferation of HNSCC cells in vitro. To determine whether TGF-alpha expression contributes to tumor growth in vivo, cationic liposome-mediated gene transfer was used to deliver an antisense expression construct targeting the human TGF-alpha gene into human head and neck tumor cells, grown as subcutaneous xenografts in nude mice. The TGF-alpha antisense gene was immediately detected in the cytoplasm of the tumor cells, translocated to the nucleus by 12 h and remained localized to the nucleus for up to 3 days. Direct inoculation of the TGF-alpha antisense (but not the corresponding sense) construct into established HNSCC tumors resulted in inhibition of tumor growth. Sustained antitumor effects were observed for up to 1 year after the treatments were discontinued. Down-modulation of TGF-alpha was accompanied by increased apoptosis in vivo. These experiments indicate that interference with the TGF-alpha/EGFR autocrine signaling pathway may be an effective therapeutic strategy for cancers which overexpress this ligand/receptor pair.

Intralesional radiolabeled human monoclonal IgM in human tumor xenografts

BACKGROUND AND PURPOSE

Intralesional (i.l.) administration of radiolabeled human monoclonal IgM could provide a new method for increasing the radiation dose delivered to a tumor without exceeding normal tissue tolerance.

MATERIALS AND METHODS

Nude mice with subcutaneous human head and neck squamous cell carcinoma nodules were injected either intralesionally or intravenously with a tumor-reactive human monoclonal IgM (CR4E8) labeled with indium-111 (111In) or yttrium-90 (90Y). Groups of mice were sacrificed at different time points and their tumors and major organs were excised and counted for radioactivity. Additional mice that were treated with i.l. 90Y-labeled CR4E8 were sacrificed at the same time points for tumor autoradiography. Serial whole-body gamma camera images were obtained from additional mice treated with i.l. 111In-labeled CR4E8. Intralesionally administered 111In-labeled irrelevant IgM (CH-1B9) and 90Y-aggregate served as specificity controls.

RESULTS

Intralesional administration of radiolabeled IgM resulted in prolonged high tumor radioactivity with little normal tissue uptake, with kidney and liver having the highest values. The biodistribution of i.l. CR4E8 was similar whether labeled with 111In or 90Y. Tumor uptake of i.l. irrelevant IgM appeared to be lower and tumor retention appeared to be shorter. Intravenous administration of tumor-reactive IgM resulted in very low tumor radioactivity with high liver and moderate spleen uptake. The i.l. administration of 90Y-aggregate produced prolonged high tumor radioactivity with little normal tissue uptake, with bone having the highest value. Tumor autoradiographs demonstrated that the radiolabeled IgM diffused through the tumor over time while the 90Y-aggregate remained localized at the injection site. Gamma camera scintigraphy corroborated the results of the biodistribution studies.

CONCLUSIONS

Intralesional but not intravenous administration of 111In- or 90Y-labeled human IgM results in high tumor radioactivity with low normal tissue exposure. Myelotoxicity is not anticipated to be the dose-limiting normal tissue toxicity of this treatment. Further development of human IgM for the i.l. treatment of human malignancies appears to be warranted.

Lack of toxicity associated with the systemic administration of antisense oligonucleotides for treatment of rats bearing LNCaP prostate tumors

Antisense oligonucleotides (oligos) are now in clinical trials for the treatment of a variety of diseases. However, concern is sometimes expressed as to the toxicity of such compounds, particularly those with phosphorothioated backbones. We have previously reported (J. Surg. Oncol. 62, 194, 1996) our experience in treating nude mice bearing human PC-3 prostate tumors with phosphorothioated antisense oligos directed against mRNA encoding transforming growth factor-alpha (TGF-alpha) and the epidermal growth factor receptor (EGFR). This therapy resulted in a 75% (9/12) response rate for the intralesional treatment and a 100% (3/3) response rate for the systemic administration utilizing Alzet diffusion pumps. In the current study, athymic nude rats bearing orthotopically implanted LNCaP tumors, whose establishment was confirmed by the expression of human PSA, were implanted subcutaneously with Alzet diffusion pumps and treated systemically for 14 days with a total of 1 mg of each oligo (2 mg total). Controls consisted of five untreated rats similarly inoculated with LNCaP cells, but which did not receive antisense oligos. After 2 weeks the rats were sacrificed and serum samples were evaluated for BUN, creatinine, LDH and SGOT. Lungs, kidneys, livers, spleens and prostates were also removed for pathologic evaluation. There were no serum marker differences between groups nor was there histologic evidence of oligo toxicity seen in any evaluated tissue. Of interest was the observation that the livers and spleens, as well as prostates, of treated animals revealed mild lymphocytic infiltration compared to controls. We conclude that at this level of administration, there is no toxicity associated with 14-day oligo treatment.

Enhanced expression of bcl-2 following antisense oligonucleotide mediated growth factor deprivation

Although the role of bcl-2 in apoptosis has been described, its involvement in prostate cancer (CAP) progression is less well understood, but thought to be involved with the transition of CAP from androgen-sensitivity to androgen-independence, where its expression is augmented following androgen ablation. For treating these recurrent androgen-independent tumors, following hormone treatment failure, a new tier of therapy based upon growth factor deprivation has been suggested, implemented by antisense oligonucleotides (oligos) directed against mRNA encoding a critical growth regulatory autocrine loop (comprised of transforming growth factor-alpha (TGF-alpha) and its binding site, the epidermal growth factor receptor (EGFR). To determine whether oligo-induced growth factor deprivation therapy similarly enhanced expression of bcl-2 (as follows androgen deprivation) human prostate cancer derived PC-3 cells were treated in vitro with oligos directed against TGF-alpha (MR-1) and/or EGFR (MR-2). After 5 days of treatment cells were immunochemically stained for human bcl-2. In similar experiments, cells were treated for 3 days prior to extraction of proteins, Western blot analysis, photography and computer evaluation of protein density by SigmaScan software. Immunostained cells treated with oligos directed against mRNA encoding TGF-alpha (MR-1) either alone or in combination with that directed against EGFR (MR-2) had increased bcl-2 expression (+3 to +5). In addition, the intensity of Western blots scanned for bcl-2 expression were 19%, 32% and 30% greater in cells treated with oligos directed against TGF-alpha, EGFR or their combination, respectively. We conclude that enhanced bcl-2 expression followed antisense oligo induced growth factor deprivation. This result is similar to that found upon androgen deprivation therapy, and also demonstrates additional biologic activity of this new class of molecular therapeutic agents.