It is not possible to 'cancel' a published transaction. After you publish a transaction to the network, all of the nodes will relay your transaction, so that eventually they (should) all know of your transaction. If you tried to publish a 'cancel request', you would have no guarantee that every single node would hear about that request, and even if they did, they may not be incentivized to listen to it. So 'cancelling' a transaction is not part of the protocol.

Your transaction included a low fee, and so it has not yet confirmed. Eventually, the network's nodes may all 'forget' about your transaction, so you could then re-spend the coins to an address you control. Take a look at this question for more info on unconfirmed transactions.