Toshimitsu Konno

Mechanism of tumor-targeted delivery of macromolecular drugs, including the EPR effect in solid tumor and clinical overview of the prototype polymeric drug SMANCS.

This review article describes three aspects of polymeric drugs. The general mechanism of the EPR (enhanced permeability and retention) effect and factors involved in the effect are discussed, in view of the advantages of macromolecular therapeutics for cancer treatment, which are based on the highly selective EPR-related delivery of drug to tumor. Also described are advantages of more general water-soluble polymeric drugs as primary anticancer agents, using SMANCS as an example. Last, SMANCS/Lipiodol is discussed with reference to the type of formulation for arterial injection with most pronounced tumor selective delivery, as well as its advantages, precautions, and side effects from the clinical standpoint.

Effect of arterial administration of high-molecular-weight anticancer agent SMANCS with lipid lymphographic agent on hepatoma: a preliminary report.

A clinical evaluation of arterial infusion of high-molecular-weight antitumor agent SMANCS dissolved in lipid lymphographic agent (thiodol) in 44 patients with mostly unresectable hepatoma is described. The treatment regimen demonstrated significant merits both therapeutically and diagnostically. Marked antitumor effects were shown in the decreased serum alpha-fetoprotein levels (86% of cases) and tumor size (95% of cases), and in survival period and histological findings. Furthermore, there was increased diagnostic sensitivity using CT scan, plain X-rays or ultrasound. The procedure of selective arterial administration of 3-4 mg of SMANCS in 3-4 ml of ethiodol per dose was simple to perform and was required only once every 3-4 weeks. Both ethiodol and the drug accumulated more selectively in tumor than in any other tissues and their activity remained for more than 3 weeks. Only minimal side-effects were associated with SMANCS and ethiodol during this study.

Selective targeting of anti-cancer drug and simultaneous image enhancement in solid tumors by arterially administered lipid contrast medium

Twenty‐four patients with various solid tumors including metastatic liver cancer and cancer of the lung, gallbladder, and pancreas were treated with a lipophilic macromolecular drug, copoly(styrene‐maleic acid) conjugated neocarzinostatin (SMANCS). The drug was dissolved in a lipid contrast medium Lipiodol and administered by catheterizing the respective feeding arteries under x‐ray monitoring. The advantages of this therapy include: (1) selective deposition of Lipiodol with the anti‐cancer drug in the target tumor, (2) a pronounced and long‐lasting anti‐cancer effect, (3) enhanced visulization of the tumor on x‐ray examinations for a prolonged period which also facilitated the long‐term follow‐up, (4) semiquantitative evaluation of the dosage regimen by x‐ray examination before further administration, (5) general applicability due to procedural simplicity, and (6) little side effect. Since the amount of Lipiodol and SMANCS used per administration for a patient (1.0–5.0 ml; 1.0–5.0 mg) was far less that the anticipated toxicity (LD50 of Lipiodol = 95 ml/60 kg, dog, intravenously; and that of SMANCS = 3.4 mg/kg, mouse, IV), no deleterious effects to such critical organs as the brain, heart, lung, liver, or kidneys were observed upon radiologic and general clinical examination.

Studies on anticancer treatment with an oily anticancer drug injected into the ligated feeding hepatic artery for liver cancer

In six adult patients with nonresectable liver cancer, as well as in mature New Zealand white rabbits with implanted VX2 carcinoma in the liver, the artery feeding the hepatic lobe with the malignant lesion was ligated, and an oily contrast medium (Lipiodol Ultra‐Fluid) was injected into the hepatoproximal lumen of the ligated artery of the liver with carcinoma. The oily contrast medium was detected in all the branches of the artery injected, and thereafter was found only in tumor tissue for 7 days experimentally and for 16 months clinically. Taking advantage of this phenomenon, the therapeutic effect of the injection of an oily anticancer drug (bleomycin oil suspension) into the hepatoproximal lumen of the ligated hepatic artery was investigated in rabbits with VX2 carcinoma of the liver. The mean concentration level of bleomycin in the tumor tissue was 2.4 ± 0.4 μg/g 1 week after the injection of bleomycin oil suspension (1.5 mg potency/kg) in three rabbits. However, its concentration level in nontumorous tissue of the liver was undetectably low in two rabbits, but 0.6 μg/g in the third rabbit. The group of rabbits receiving an injection of bleomycin oil suspension into the ligated artery had a significantly longer mean survival time than those of the experimental group receiving an injection of saline solution of bleomycin into the ligated artery as well as the three other groups treated (P < 0.02, N = 5 for each group). It may be concluded that an oily anticancer drug injected into the hepatoproximal lumen of the ligated hepatic artery can intensify the anticancer effects of a ligation of the hepatic artery for liver cancer. Cancer 52:2193‐2200, 1983.

Image enhancement in computerized tomography for sensitive diagnosis of liver cancer and semiquantitation of tumor selective drug targeting with oily contrast medium

A new type of anticancer agent with an amphiphilic nature, poly(styrene‐co‐maleic acid)‐conjugated neocarzinostatin (Smancs), was dissolved in lipid contrast medium Lipiodol (Smancs/Lpd, Gelbet Co., Paris, France). This medium was injected arterially and found to be an invaluable tool for highly sensitive computerized tomography (CT) image analysis of tumors. After the administration, CT images revealed high‐density areas which corresponded to the location and size of liver cancer, the smallest being 4 mm in diameter. The deposition pattern of Smancs/Lpd in liver cancers by CT was classified into three types. In type A, Lipiodol was distributed relatively even in the tumor lesion, whereas in type B it was accumulated predominantly around the tumors periphery although the central portion remaining low in density. A few cases exhibited type C pattern, which was a mixture of types A and B. Type A was found essentially in primary liver cancer, and types B and C in secondary liver cancer. Thus, the CT pattern was found to be useful for differential diagnosis. For a sufficient therapeutic effect, 0.08 ml of Smancs/Lpd per cm2 of the maximal CT cross‐section of the tumor area was found to be necessary. As a routine protocol after Smancs/Lpd administration, CT scanning was recommended for primary liver cancer initially at 1 week and then once every month. Secondary liver cancer required more frequent CT follow‐ups after the administration (on the third day, after 1 and 2 weeks, and every month) due to relatively rapid disappearance of the stain than in the primary liver cancer.

Targeting cancer chemotherapeutic agents by use of lipiodol contrast medium

Arterially administered Lipiodol Ultrafluid contrast medium selectively remained in various malignant solid tumors because of the difference in time required for the removal of Lipiodol contrast medium from normal capillaries and tumor neovasculature. Although blood flow was maintained in the tumor, even immediately after injection Lipiodol contrast medium remained in the neovasculature of the tumor. To target anti‐cancer agents to tumors by using Lipiodol contrast medium as a carrier, the characteristics of the agents were examined. Anti‐cancer agents had to be soluble in Lipiodol, be stable in it, and separate gradually from it so that the anti‐cancer agents would selectively remain in the tumor. These conditions were found to be necessary on the basis of the measurement of radioactivity in VX2 tumors implanted in the liver of 16 rabbits that received arterial injections of 14C‐labeled doxorubicin. Antitumor activities and side effects of arterial injections of two types of anti‐cancer agents were compared in 76 rabbits with VX2 tumors. Oily anti‐cancer agents that had characteristics essential for targeting were compared with simple mixtures of anti‐cancer agents with Lipiodol contrast medium that did not have these essential characteristics. Groups of rabbits that received oily anti‐cancer agents responded significantly better than groups that received simple mixtures, and side effects were observed more frequently in the groups that received the simple mixtures. These results suggest that targeting of the anti‐cancer agent to the tumor is important for treatment of solid malignant tumors.

Tailor-making of protein drugs by polymer conjugation for tumor targeting: A brief review on smancs

Chemical conjugation of poly(styrene-co-maleic acid) to an antitumor protein (neocarzinostatin) yielded an entirely new derivative designated as smancs (polystyrene-maleic acid conjugated neocarzinostatin). The purpose of the modification was to improve its pharmacological properties; the resulting conjugate exhibited much higher tumoritropism and lymphotropism, enhancedin vivo stability (about ten times), higher chemotherapeutic index (lower toxicity), and decreased antigenicity. Another advantage associated with this molecular engineering was an increased hydrophobicity. By this character it was solubilized in lipid contrast medium LipiodolR, which facilitated highly sensitive detection under x-ray-accompanying selective anticancer effectin situ. Three factors were responsible for such improvements: molecular size, hydrophobicity, and polyanionic nature. Most of the known drugs so far used as therapeutic agents are less than 1000 daltons, and those with larger molecular weights have been explored much less extensively. By polymer conjugation, the size of the drug can be extended to about 15,000 daltons (macromolecular therapeutics). The most outstanding characteristic of smancs (16,000 daltons) was the tumoritropicity, which may be a result of the highly developed neovasculature of solid tumors. Smancs as a prototype drug thus appears to lead the way in cancer drug targeting.

Kinin‐generating Cascade in Advanced Cancer Patients and in vitro Study

The role of the bradykinin‐generating system in the pathogenesis of cancer was explored by simultaneously measuring plasma prekallikrein (PK), the precursor of kallikrein, which is the major enzyme responsible for kinin generation, and plasma kininogens (KNG), which are precursors of kinin, in patients with various cancers. The mean value of plasma PK in healthy volunteers was 2.5 ± 0.5 (mean ± SD) units/mg plasma protein and that in cancer patients (all stage IV) was 1.7 ± 0.7 units/ mg plasma protein. The mean value of plasma KNG in healthy volunteers was 12.5 ± 2.0 ng kinin equivalents/mg plasma protein and that in cancer patients was 10.9 ± 2,8 ng. These data showed that plasma PK and plasma KNG values were significantly lower in cancer patients compared with healthy volunteers (P < 0.0005 for PK; 0.0005 < P < 0.005 for KNG; n = 28 for healthy subjects; n = 29 for cancer patients). These data appear to indicate that conversion of PK to kallikrein would probably occur with concomitant consumption of KNG by newly generated kallikrein for kinin generation in cancer patients. Early stage cancer patients showed little difference from healthy volunteers. For the in vitro study, activation of purified Hageman factor (HP) and PK was examined by using cancer cell lines and virus‐transformed cells that produced plasminogen activator (PA) at a high rate. Both HF and PK were activated in the presence of plasminogen. Diploid cell lines and primary fibroblasts, which did not produce PA, activated neither HF nor PK. Taking all these data together, we conclude that kinin generation does occur in the plasma of patients with advanced cancer, and that one of the initiation mechanisms of the kinin‐generating cascade appears to be mediated by plasmin and to depend on cancer cell‐derived PA activity.

Anticancer effects of arterial administration of the anticancer agent SMANCS with lipiodol on metastatic lymph nodes

A new method of arterially administering an oily anticancer agent was successfully established for the selective targeting of metastatic lymph nodes. A high molecular weight anticancer agent, a conjugate of copolymer (styrene maleic acid) to neocarzinostatin (SMANCS) was prepared in our laboratory and dissolved in a lymphographic oily contrast medium, Lipiodol (SMANCS/Lipiodol). SMANCS/Lipiodol was administered intraoperatively to eight patients with colorectal cancer and preoperatively to one patient with gastric cancer with lymph node metastases. In six of the patients with colorectal cancer, the drug was administered via an artery and in the other two patients the drug was injected into the wall of the colon near the primary cancer. In the patient with gastric cancer, the drug was administered via the left gastric artery. Delivery of the drug to the lymph nodes was examined roentgenologically and the anticancer effect was examined histologically. The results showed that SMANCS/Lipiodol could be delivered to the metastatic lymph node via the artery, but it could not be delivered to the metastatic lesion of the lymph node via the lymphatic route. In the patient with gastric cancer, SMANCS/Lipiodol preoperatively administered via an artery was found to remain selectively in a metastatic lymph node and an anticancer effect was histologically proved in all three of the metastatic lymph nodes.

Treatment of carcinoma of the gallbladder in Japan

Clinical records of 2567 patients (1717 female and 850 male) with primary carcinoma of the gallbladder in Japan, during the past 19 years, were collected by questionnaires sent out to the main 100 surgical institutes in Japan. Eighty-seven per cent of the patients were over fifty years of age. Gallstones were found in 58.8% of 1496 patients. About 50% of the patients with gallstones had cholesterol group stones. Of the 2269 patients who underwent surgical interventions, radical operations were performed in 467 patients (20.6%). Of the 467 patients, a correct preoperative diagnosis was made in only 77 patients (16.3%). Patients in Nevins Stages I and II, whose lesions had been confined to the muscle layer, showed a good survival rate with only simple cholecystectomy or extended cholecystectomy, while the patients in Stages III, IV and V, whose lesions had spread beyond the muscle layer, showed poor results even with more aggressive surgical approaches. The poor prognosis of the lesions in Stages III, IV and V might be due to inappropriate aggressive procedures. For the lesions involving all the layers of the gallbladder wall, radical resection, such as extended cholecystectomy plus pancreatoduodenectomy, or extended right lobectomy plus pancreatoduodenectomy, might be recommended.