this invention relates to a pharmaceutical composition for the treatment of leukemia which comprises as an active ingredient a 9 - cis - retinoic acid - α - tocopherol ester represented by the formula ( i ) ## str1 ## and a pharmaceutical carrier thereof . moreover , this invention relates to a pharmaceutical composition for the treatment of leukemia which comprises as an active ingredient a combination of a 9 - cis - retinoic acid - α - tocopherol ester represented by the above formula ( i ) with vd 3 . furthermore , this invention relates to a pharmaceutical composition for the treatment of leukemia which comprises as an active ingredient a combination of a 9 - cis - retinoic acid - α - tocopherol ester represented by the above formula ( i ) with 9 - cis - ra . this invention also relates to a method for the treatment of leukemia which comprises administering to a patient suffering from leukemia a therapeutically effective amount of a 9 - cis - retinoic acid - α - tocopherol ester represented by the above formula ( i ). further , the invention relates to a method for the treatment of leukemia which comprises administering to a patient suffering from leukemia a therapeutically effective amount of 9 - cis - retinoic acid - α - tocopherol ester together with vd 3 at a sufficiently low dose not to produce side effects . furthermore , the invention relates to a method for the treatment of leukemia which comprises administering to a patient suffering from leukemia a therapeutically effective amount of 9 - cis - retinoic acid - α - tocopherol ester together with 9 - cis - ra at a sufficiently low dose not to produce side effects . japanese patent publication 60 - 56156 discloses that 9 - cis - retinoic acid - α - tocopherol ester can be obtained by light - isomerisation of all - trans α - tocopherol vitamin a acid . commercially it may be prepared by an esterification of 9 - cis - ra with α - tocopherol . the esterification of 9 - cis - ra with α - tocopherol may be carried out according to any well - known esterification processes , for example , the process as disclosed in our japanese patent kokai 5 - 202020 . the term &# 34 ; α - tocopherol &# 34 ; as used herein refers to dl - α - tocopherol , d - α - tocopherol and l - α - tocopherol . also , the term &# 34 ; a 9 - cis - retinoic acid - α - tocopherol ester represented by the formula ( i )&# 34 ; as used herein refers to all possible optical isomers , racemates and racemic mixtures thereof . these possible , optically active substances may be prepared , for example , according to chiral synthesis using optically active starting materials . as stated above , the 9 - cis - retinoic acid - α - tocopherol ester of this invention itself may exert biological activities to inhibit the proliferation of leukemia cells and induce the differentiation of the said cells . moreover , a synergistic effect can be achieved by using the present 9 - cis - retinoic acid - α - tocopherol ester together with vd 3 or 9 - cis - ra , while a dose of vd 3 or 9 - cis - ra can be reduced to prevent vd 3 or 9 - cis - ra from developing inherent side effects thereto . the leukemia to which the present therapeutic agent is to be clinically applied includes hematological tumors , that is , leukemia , especially acute promyelocytic leukemia , and lymphoma . for the treatment of leukemia , therapeutically effective serum concentration of the 9 - cis - retinoic acid - α - tocopherol ester in an adult patient weighing 60 kg usually ranges from 1 × 10 - 9 m to 5 × 10 - 5 m in order that the present ester may sufficiently exert its effect . thus , a specific daily dose for adults to meet the requirement for the serum concentration as stated above may be preferably in the range of from 10 mg to 1200 mg , more preferably from 60 mg to 600 mg , in terms of the 9 - cis - retinoic acid - α - tocopherol ester . the present therapeutic agent which comprises as an active ingredient a combination of the present 9 - cis - retinoic acid - α - tocopherol ester with vd 3 should be administered at such a dose that can sufficiently exert a synergistic effect of both the ingredients , while the vd 3 should be administered at a sufficiently low dose not to produce its side effects , that is to say , at such a dose that its serum concentration in a patient should be 10 - 9 m or less . a serum concentration of the 9 - cis - retinoic acid - α - tocopherol ester in an adult patient weighing 60 kg usually ranges from 1 × 10 - 9 m to 5 × 10 - 5 m in order that the synergistic effect may sufficiently be exerted . thus , a specific daily dose for adults to meet the requirements for both the serum concentrations as stated above may be preferably in the range of from 10 mg to 1200 mg , more preferably from 60 mg to 600 mg in terms of the 9 - cis - retinoic acid - α - tocopherol ester and in the range of from 0 . 005 μg to 5 μg , more preferably from 0 . 01 μg to 0 . 50 μg in terms of vd 3 . it is essential to administer both the ingredients concomitantly . the present therapeutic agent which comprises as an active ingredient a combination of the present 9 - cis - retinoic acid - α - tocopherol ester with 9 - cis - ra should be administered at such a dose that can sufficiently exert a synergistic effect of both the ingredients , while the 9 - cis - ra should be administered at a sufficiently low dose not to produce its side effects , that is to say , at such a dose that its serum concentration in a patient should be 10 - 7 m or less . a serum concentration of the 9 - cis - retinoic acid - α - tocopherol ester in an adult patient weighing 60 kg usually ranges from 1 × 10 - 9 m to 5 × 10 - 5 m in order that the synergistic effect may sufficiently be exerted . then , a specific daily dose for adults to meet the requirements for both the serum concentrations as stated above may be preferably in the range of from 10 mg to 1200 mg , more preferably from 60 mg to 600 mg , in terms of the 9 - cis - retinoic acid - α - tocopherol ester and in the range of from 1 . 0 mg to 80 mg , more preferably from 5 . 0 mg to 20 mg in terms of 9 - cis - ra . it is essential to administer both the ingredients concomitantly . the therapeutic agent for leukemia according to the present invention may typically be administered via oral , intravenous , subcutaneous , intramuscular or rectal route , and intravenous or oral administration is preferable . a pharmaceutical composition for treating leukemia according to this invention may be prepared according to any conventional preparation methods . a pharmaceutical preparation for oral administration may include various dosage forms , for example , tablets , granules , powders , hard capsules , soft capsules , liquid preparations for oral administration , etc . a pharmaceutical preparation for parenteral administration may include various dosage forms , for example , injections , suppositories , etc . these dosage forms can be prepared by any conventional methods using additives commonly used for pharmaceutical preparations , if desired , such as excipients , stabilizers , antiseptics , solubilizers , wetting agents , emulsifying agents , lubricants , sweetening agents , coloring agents , flavors , antioxidants and the like . specific examples of these additives may include starch , sucrose , fructose , lactose , glucose , mannitol , sorbitol , precipitated calcium carbonate , crystalline cellulose , carboxymethylcellulose , dextrin , gelatin , acacia , magnesium stearate , talc , hydroxypropylmethylcellulose and the like . for injections or liquid preparations , the active ingredient may be used in the form of a solution or suspension thereof in a conventional diluent . typical examples of the diluent may include physiological saline solution , ringer solution , aqueous glucose solution , alcohols , fatty acid esters , glycols , glycerol , fatty acid glycerides , fats derived from animal and plant sources , paraffins and the like . injections may be prepared according to any conventional methods using additives , if required , such as ph adjusters , buffers , stabilizers , preservatives , solubilizing agents and the like . this invention will be more fully illustrated by way of the following preparation example , examples and formulation examples . however , these examples are not to be considered as limiting the present invention . the medicines and reagents used in the following examples were available as stated below : dimethyl sulfoxide ( hereinafter referred to as &# 34 ; dmso &# 34 ;) and vd 3 were available from wako pure chemical industries , ltd . atra was available from sigma chemical co . 9 - cis - ra was available from biomol research laboratories or basf ( via nisshin badische ). nitro blue tetrazolium ( hereinafter referred to as &# 34 ; nbr &# 34 ;) and phorbol - 12 - myristate - 13 - acetate ( hereinafter referred to as &# 34 ; tpa &# 34 ;) were available from sigma chemical co . to a solution of 50 mg ( 0 . 1664 mmol ) of 9 - cis - retinoic acid ( 9 - cis - ra ) in diisopropyl ether ( 5 ml ) was added 26 μl ( 0 . 1831 mmol ) of trifluoroacetic acid anhydride and the mixture was stirred at room temperature for 15 minutes . then , a solution of 79 mg ( 0 . 1831 mmol ) of dl - α - tocopherol in diisopropyl ether ( 5 ml ) was added dropwise and the mixture was stirred at room temperature for one hour . to the reaction mixture was added 28 % ( w / v ) aqueous ammonia ( 10 ml ) and the resulting mixture was extracted with diisopropyl ether ( 20 ml × 3 ). the combined organic layers were washed successively with water and saturated aqueous sodium chloride . the diisopropyl ether layer was dried over anhydrous sodium sulfate and the solvent was then distilled off under reduced pressure . the residue was purified by a silica gel chromatography and the fractions from hexane containing 2 % ( v / v ) diisopropyl ether gave 36 mg ( 30 %) of the title compound as a yellow oily substance . 1 h nmr ( cdcl 3 , 400 mhz ) d 0 . 82 - 0 . 90 ( m , 12h ), 1 . 00 - 2 . 20 ( m , 29h ), 1 . 05 ( s , 3h ), 1 . 55 ( s , 6h ), 1 . 66 ( s , 3h ), 1 . 98 ( s , 3h ), 2 . 03 ( s , 6h ), 2 . 09 ( s , 3h ), 2 . 40 ( s , 3h ), 2 . 59 ( t , j = 6 . 8 hz , 2h ), 6 . 08 ( s , 1h ), 6 . 09 ( d , j = 10 . 7 hz , 1h ), 6 . 29 ( d , j = 13 . 2 hz , 1h ), 6 . 33 ( d , j = 14 . 2 hz , 1h ), 6 . 67 ( d , j = 15 . 6 hz , 1h ), 7 . 15 ( dd , j = 11 . 7 hz , 15 . 0 hz , 1h ) the cultured cell used for the following determination and examples was the nb4 cell , i . e ., the cultured cell of human myelomonocytic leukemia , which was given from professor h . phillip koeffler of cedars - sinai medical center / ucla school of medicine , los angels , u . s . a . ( blood , vol . 77 , 1080 , 1991 ) and used here after suspending and incubating in rpmi 1640 medium ( manufactured by gibco brl ) containing 10 % fetal bovine serum ( hereinafter referred to as &# 34 ; fbs &# 34 ;) and 80 μg / ml gentamicin at 37 ° c . in a moist air containing 5 % co 2 . the above cultured cells were incubated in a culture plate under the same conditions as described above with the addition of 9 - cis - retinoic acid - α - tocopherol ester alone or in combination with vd 3 , atra or 9 - cis - ra . the number of cultured cells was measured by means of coulter counter type zm ( manufactured by coulter electronics co ., ltd ., u . k .). nbt reducing activity values were measured as a standard for the differentiation induction of the cultured cells of myelomonocytic leukemia according to the following method : 1 ) preparation of nbt test solution : to 100 ml of rpmi 1640 medium containing 10 % fbs was added a solution of 100 mg of nbt in 1 ml of dmso and then 100 μl of a dmso solution of tpa at 100 μg / ml , and the resulting mixture was stirred well to prepare a nbt test solution . 2 ) the cultured cells were placed into a 10 ml - test tube and the number of the cultured cells was measured . thereafter , the test tube was centrifuged , a supernatant was discarded and then 1 ml aliquot of the said nbt test solution was added to each test tube . the resulting mixture was shaken at 37 ° c . for 30 minutes . the reaction was discontinued by adding 0 . 3 ml of 5n hydrochloric acid and then the mixture was allowed to stand at room temperature for 1 - 2 hours . the cultured cell suspension thus obtained was centrifuged to remove a supernatant , 0 . 7 ml of dmso was added and then absorbance was measured at 560 nm by means of a spectrophotometer ( type u - 2000 , manufactured by hitachi , ltd .). the measured data was converted to the absorbance per 1 cultured cells , which was designated as a nbt reducing activity value . an increased nbt reducing activity value means a promoted differentiation induction of leukemia cells . combined effect of 9 - cis - retinoic acid - α - tocopherol ester and vd 3 on the differentiation induction of nb4 cells to nb4 cells ( 2 × 10 5 cells / ml ) used as the cultured cell was added vd 3 so as to provide concentrations of 3 × 10 - 9 m , 3 × 10 - 8 m and 3 × 10 - 7 m , respectively , and then 9 - cis - retinoic acid - α - tocopherol ester was further added so as to provide a concentration of 3 × 10 - 6 m . incubation was carried out for 4 days to investigate the combined effect on the differentiation induction of the cells . for comparison , the cultured cells not containing any 9 - cis - retinoic acid - α - tocopherol ester and those containing tretinoin tocoferil ( 3 × 10 - 6 m ) instead of the 9 - cis - retinoic acid - α - tocopherol ester were similarly incubated . the effect on the differentiation induction of the cells was investigated by measuring nbt reducing activity values . the results are shown in fig1 . in fig1 the abscissa and ordinate indicate concentrations of vd 3 and absorbances ( i . e ., nbt reducing activity values ) per 10 7 cultured cells , respectively . the line represented by (--) shows a relationship between concentrations of vd 3 and nbt reducing activity values when vd 3 was used alone , the line represented by (-▪-) shows a relationship between concentrations of vd 3 and nbt reducing activity values when 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ) was used together with vd 3 , and the line represented by (-▴-) shows a relationship between concentrations of vd 3 and nbt reducing activity values when tretinoin tocoferil ( 3 × 10 - 6 m ) was used together with vd 3 . fig1 shows that a nbt reducing ability was not increased in a concentration range of up to 3 . 0 × 10 - 6 m when vd 3 was used alone , while tretinoin tocoferil ( 3 × 10 - 6 m ), when used together , potentiated a nbt reducing ability by vd 3 , but its potentiating ability was limited to approximately three - fold level at 3 × 10 - 9 m of vd 3 . on the other hand , 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ), when used together , potentiated a nbt reducing ability by vd 3 and its potentiating ability was raised to approximately 7 . 5 - fold level at 3 × 10 - 9 m of vd 3 . accordingly , it is clearly demonstrated that 9 - cis - retinoic acid - α - tocopherol ester could noticeably potentiate the differentiation of nb4 cells by vd 3 and its potentiating effect was far more strong as compared with tretinoin tocoferil . combined effect of 9 - cis - retinoic acid - α - tocopherol ester and 9 - cis - ra on the inhibition of nb4 cell proliferation to nb4 cells ( 5 × 10 5 cells / ml ) used as the cultured cell was added 9 - cis - ra ( 3 × 10 - 9 m ) and then 9 - cis - retinoic acid - α - tocopherol ester was further added so as to provide a concentration of 3 × 10 - 6 m . incubation was carried out for 4 days to investigate the inhibitory effect on the cell proliferation . for comparison , the cultured cells not containing both 9 - cis - retinoic acid - α - tocopherol ester and 9 - cis - ra ( control ), those not containing any 9 - cis - retinoic acid - α - tocopherol ester and those containing tretinoin tocoferil ( 3 × 10 - 6 m ) instead of the 9 - cis - retinoic acid - α - tocopherol ester were similarly incubated . after 4 days , the number of the cells was counted and expressed in terms of a relative percent calculated from the cell number of the control defined as 100 . the results are shown in fig2 . in fig2 the symbols of none and 9cra shown beneath the abscissa represent the group not given 9 - cis - ra and the group given 9 - cis - ra , respectively . the columns from the left to the right in order represent the control ( not given any active agents ), the group given tretinoin tocoferil alone ( 3 × 10 - 6 m ), the group given 9 - cis - retinoic acid - α - tocopherol ester alone ( 3 × 10 - 6 m ), the group given 9 - cis - ra alone ( 3 × 10 - 9 m ), the group given concomitantly 9 - cis - ra ( 3 × 10 - 9 m ) and tretinoin tocoferil ( 3 × 10 - 6 m ) and the group given concomitantly 9 - cis - ra ( 3 × 10 - 9 m ) and 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ), respectively . fig2 shows that the proliferation of nb4 cells could not be inhibited with 9 - cis - ra alone ( 3 × 10 - 9 m ), while tretinoin tocoferil ( 3 × 10 - 6 m ) could inhibit the proliferation of nb4 cells when used together with 9 - cis - ra ( 3 × 10 - 9 m ), but its inhibition rate ( i . e ., a relative percent of the number of survival cells to that of the control ) was approximately 86 %. in contrast thereto , when 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ) was used together , the proliferation of nb4 cells was inhibited and its inhibition rate was approximately 72 %, which means the proliferation of nb4 cells was noticeably inhibited . accordingly , it is clearly demonstrated that the differentiation of nb4 cells can be effectively inhibited by a combined use of 9 - cis - retinoic acid - α - tocopherol ester with 9 - cis - ra and the inhibitory effect was far more potent as compared with that of tretinoin tocoferil . combined effect of 9 - cis - retinoic acid - α - tocopherol ester and 9 - cis - ra on the differentiation induction of nb4 cells to nb4 cells ( 5 × 10 5 cells / ml ) used as the cultured cell was added 9 - cis - ra ( 3 × 10 - 9 m ) and then 9 - cis - retinoic acid - α - tocopherol ester at a concentration of 3 × 10 - 6 m . incubation was carried out for 4 days . the cells were washed with a phosphate buffer and then reacted with a mouse monoclonal antibody cd11b ( obtained from nichirei corporation ) diluted with ifa buffer ( 10 mm hepes , ph 7 . 4 , 150 mm nacl , 4 % fbs , 0 . 1 % sodium azide ! at 4 ° c . for one hour . the cells were washed twice with ifa buffer and then reacted with a fitc - labeled rabbit anti - mouse antibody ( diluted with ifa buffer ) at 4 ° c . for one hour . the cells were washed twice with ifa buffer and fluorescence - positive cells were analyzed by means of a flow cytometry ( epics xl , manufactured by coulter electronics co ., ltd .). for comparison , the cultured cells not containing both 9 - cis - retinoic acid - α - tocopherol ester and 9 - cis - ra , those containing 9 - cis - ra ( 3 × 10 - 9 m ), those containing 9 - cis - retinoic acid alone ( 3 × 10 - 8 m ) and those containing tretinoin tocoferil ( 3 × 10 - 6 m ) instead of the 9 - cis - retinoic acid - α - tocopherol ester were similarly incubated and reacted with the antibodies . appearance of a differentiation marker for cd11b indicates the differentiation of the cells into a granulocyte system . the results are shown in fig3 . in fig3 the symbols of none and 9cra represent the group not given 9 - cis - ra and the group given 9 - cis - ra , respectively , while the symbols of 9cra + tt and 9cra + 9ctt represent the group given 9 - cis - ra ( 3 × 10 - 9 m ) and tretinoin tocoferil ( 3 × 10 - 6 m ) and the group given 9 - cis - ra ( 3 × 10 - 9 m ) and 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ) respectively . fig3 shows that differentiation could be far more induced when tretinoin tocoferil ( 3 × 10 - 6 m ) was further added as compared when 9 - cis - ra ( 3 × 10 - 9 m ) was used alone . further , differentiation could be much more noticeably induced when 9 - cis - retinoic acid - α - tocopherol ester ( 3 × 10 - 6 m ) was further added as compared when tretinoin tocoferil ( 3 × 10 - 6 m ) was further added and the differentiation inducing ability was equivalent to that when 9 - cis - retinoic acid ( 3 × 10 - 8 m ) was used alone . accordingly , it is clearly demonstrated that an equivalent effect can be achieved by a combination of 9 - cis - retinoic acid with 9 - cis - retinoic acid - α - tocopherol ester even if an amount of the 9 - cis - retinoic acid to be used may be reduced to 1 / 10 . inhibitory effects on proliferation of nb4 cells by 9 - cis - retinoic acid - α - tocopherol ester alone and by combined use of the ester with vd 3 to nb4 cells ( 5 × 10 5 cells / ml ) used as the cultured cell was added 9 - cis - retinoic acid - α - tocopherol ester was added ( 1 . 5 × 10 - 5 m ). incubation was carried out for 4 days . for comparison , the cultured cells not containing any active compounds and those containing tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) instead of the 9 - cis - retinoic acid - α - tocopherol ester were similarly incubated . in order to investigate the effect obtained by a combined use with vd 3 , the cultured cells containing 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) and vd 3 ( 3 × 10 - 9 m ) and for comparison those containing tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) and vd 3 ( 3 × 10 - 9 m ) were similarly incubated . the results are shown in fig4 . in fig4 the symbols of none , 9ctt and tt shown beneath the abscissa represent the group not given 9 - cis - retinoic acid - α - tocopherol ester or tretinoin tocoferil , the group given 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) and the group given tretinoin tocoferil ( 1 . 5 × 10 - 5 m ), respectively . the columns from the left to the right in order represent the control ( not given any active agents ), the group given vd 3 alone ( 3 × 10 - 9 m ), the group given 9 - cis - retinoic acid - α - tocopherol ester alone ( 1 . 5 × 10 - 5 m ), the group given vd 3 ( 3 × 10 - 9 m ) together with 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ), the group given tretinoin tocoferil alone ( 1 . 5 × 10 - 5 m ) and the group given vd 3 ( 3 × 10 - 9 m ) together with tretinoin tocoferil ( 1 . 5 × 10 - 5 m ), respectively . fig4 shows that 9 - cis - retinoic acid - α - tocopherol ester even when used alone could highly inhibit the proliferation of nb4 cells and its inhibitory effect was far more potent than that of tretinoin tocoferil when used alone . fig4 further shows that 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) could noticeably potentiate an inhibitory effect on the proliferation by vd 3 and this inhibitory effect was much more effective than that when tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) and vd 3 ( 3 × 10 - 9 m ) were used together . to nb4 cells ( 5 × 10 5 cells / ml ) used as the cultured cell was added 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) and incubation was carried out for 4 days to investigate the effect on the differentiation induction of the cells . for comparison , the cultured cells not containing 9 - cis - retinoic acid - α - tocopherol ester and those containing tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) were similarly incubated . on the other hand , for investigating the effect by a combined use with vd 3 , the cultured cells containing 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) and vd 3 ( 3 × 10 - 9 m ) and for comparison those containing tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) instead of the 9 - cis - retinoic acid - α - tocopherol ester and vd 3 ( 3 × 10 - 9 m ) were also similarly incubated . the effect on the differentiation induction of the cells was investigated by measuring nbt reducing activity values . the results are shown in fig5 . in fig5 the ordinate indicates absorbances ( nbt reducing activity values ) per 10 7 cultured cells , while the symbols of none , 9ctt and tt shown beneath the abscissa represent the group not given 9 - cis - retinoic acid - α - tocopherol ester or tretinoin tocoferil , the group given 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) and the group given tretinoin tocoferil ( 1 . 5 × 10 - 5 m ), respectively . the columns from the left to the right in order represent the control ( not given any active agents ), the group given vd 3 alone ( 3 × 10 - 9 m ), the group given 9 - cis - retinoic acid - α - tocopherol ester alone ( 1 . 5 × 10 - 5 m ), the group given 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) together with vd 3 ( 3 × 10 - 9 m ), the group given tretinoin tocoferil alone ( 1 . 5 × 10 - 5 m ), and the group given tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) together with vd 3 ( 3 × 10 - 9 m ), respectively . fig5 shows that 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 6 m ) even when used alone could noticeably raise a nbt reducing ability and this effect was far more potent than that of tretinoin tocoferil when used alone ( 1 . 5 × 10 - 5 m ). fig5 further shows that 9 - cis - retinoic acid - α - tocopherol ester ( 1 . 5 × 10 - 5 m ) could noticeably potentiate an inhibitory effect on the proliferation by vd 3 and this inhibitory effect was much more effective than that when tretinoin tocoferil ( 1 . 5 × 10 - 5 m ) and vd 3 ( 3 × 10 - 9 m ) were used together . accordingly , it is clearly demonstrated that 9 - cis - retinoic acid - α - tocopherol ester can highly induce the differentiation of nb4 cells and potentiate the differentiation of nb4 cells by vd 3 . in summary , the three types of the present pharmaceutical preparations for treating leukemia may far more effectively inhibit the proliferation of leukemia cells and noticeably promote the differentiation induction of the cells . moreover , they are still effective for the treatment of leukemia even at a serum vd 3 concentration of 10 - 9 m or less which dose not cause any side effects . in addition to this , a dose of 9 - cis - ra may be reduced to such a level not developing any side effects , which is highly useful in the treatment of leukemia . 50 g of 9 - cis - retinoic acid - α - tocopherol ester was mixed with 130 g of coconut oil to form a homogeneous solution . separately , a gelatin solution for capsule coating was prepared from 93 g of gelatin , 19 g of glycerol , 10 g of d - sorbitol ( 70 w / v %), 0 . 4 g of ethyl p - hydroxybenzoate , 0 . 2 g of propyl p - hydroxybenzoate and 0 . 4 g of titanium oxide . soft capsules were prepared from the two solutions prepared as above according to a manual plate stamping method , each capsule containing 180 mg of 9 - cis - retinoic acid - α - tocopherol ester . 5 g of 9 - cis - retinoic acid - α - tocopherol ester , a proper volume of soybean oil and 1 g of benzyl alcohol were mixed and then made up to a total volume of 100 cc with soybean oil . the resulting solution was aseptically injected portionwise into ampoules in each portion of 2 cc and then the ampoules were sealed . 50 g of 9 - cis - retinoic acid - α - tocopherol ester and 5 μg of vd 3 were mixed with 130 g of coconut oil to form a homogeneous solution . separately , a gelatin solution for capsule coating was prepared from 93 g of gelatin , 19 g of glycerol , 10 g of d - sorbitol ( 70 w / v %), 0 . 4 g of ethyl p - hydroxybenzoate , 0 . 2 g of propyl p - hydroxybenzoate and 0 . 4 g of titanium oxide . soft capsules were prepared from the two solutions prepared as above according to a manual plate stamping method , each capsule containing 180 mg of 9 - cis - retinoic acid - α - tocopherol ester and 0 . 018 μg of vd 3 . 5 g of 9 - cis - retinoic acid - α - tocopherol ester , 0 . 5 μg of vd 3 , a proper volume of soybean oil and 1 g of benzyl alcohol were mixed and then made up to a total volume of 100 cc with soybean oil . the resulting solution was aseptically injected portionwise into ampoules in each portion of 2 cc and then the ampoules were sealed . 50 g of 9 - cis - retinoic acid - α - tocopherol ester and 2 . 8 g of 9 - cis - ra were mixed with 130 g of coconut oil to form a homogeneous solution . separately , a gelatin solution for capsule coating was prepared from 93 g of gelatin , 19 g of glycerol , 10 g of d - sorbitol ( 70 w / v %), 0 . 4 g of ethyl p - hydroxybenzoate , 0 . 2 g of propyl p - hydroxybenzoate and 0 . 4 g of titanium oxide . soft capsules were prepared from the two solutions prepared as above according to a manual plate stamping method , each capsule containing 180 mg of 9 - cis - retinoic acid - α - tocopherol ester and 10 mg of 9 - cis - ra . 5 g of 9 - cis - retinoic acid - α - tocopherol ester , 280 mg of 9 - cis - ra , a proper volume of soybean oil and 1 g of benzyl alcohol were mixed and then made up to a total volume of 100 cc with soybean oil . the resulting solution was aseptically injected portionwise into ampoules in each portion of 2 cc and then the ampoules were sealed .
9 - cis - retinoic acid - α - tocopherol esters , pharmaceutical compositions containing the same and use of the same as a medicine for the treatment of leukemia , in particular , the remission of leukemia are provided and a combined use of a 9 - cis - retinoic acid - α - tocopherol ester and either 1α , 25 - dihydroxyvitamin d 3 or 9 - cis - retinoic acid exhibits a synergistic effect in the treatment of leukemia without any side effects caused by 1α , 25 - dihydroxyvitamin d 3 or 9 - cis - retinoic acid .